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Late Ordovician brachiopods from the Chingiz Terrane, Kazakhstan, and their palaeogeography a

b

Leonid E. Popov & L. Robin M. Cocks a

Department of Geology, National Museum of Wales, Cathays Park, Cardiff, CF10 3NP United Kingdom b

Department of Earth Sciences, The Natural History Museum, Cromwell Road, London, SW7 5BD, United Kingdom Published online: 06 Feb 2014.

Click for updates To cite this article: Leonid E. Popov & L. Robin M. Cocks (2014) Late Ordovician brachiopods from the Chingiz Terrane, Kazakhstan, and their palaeogeography, Journal of Systematic Palaeontology, 12:6, 687-758, DOI: 10.1080/14772019.2013.837844 To link to this article: http://dx.doi.org/10.1080/14772019.2013.837844

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Journal of Systematic Palaeontology, 2014 Vol. 12, No. 6, 687–758, http://dx.doi.org/10.1080/14772019.2013.837844

Late Ordovician brachiopods from the Chingiz Terrane, Kazakhstan, and their palaeogeography Leonid E. Popova* and L. Robin M. Cocksb a

Department of Geology, National Museum of Wales, Cathays Park, Cardiff, CF10 3NP, United Kingdom; bDepartment of Earth Sciences, The Natural History Museum, Cromwell Road, London, SW7 5BD, United Kingdom

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(Received 12 October 2012; accepted 22 May 2013; first published online 6 February 2014) The Late Ordovician Akdombak Formation of the Chingiz-Tarbagatai Terrane, Kazakhstan, has yielded brachiopods from four successive horizons, three Katian and the upper one of Hirnantian age. Comparable faunas of an earlier Katian age are also described from the upper part of the Taldyboi Formation, also within the Chingiz-Tarbagatai Terrane, but there are no Hirnantian rocks there. The new subfamily Alpeisinae is erected within the Wangyuiidae (Plectorthoidea), and the following new genera are introduced: Holmerglossa (Linfguloidea), Wrightiops (Craniopsoidea), Buminomena (Strophomenoidea), Alpeis, Ashinaorthis and Enbektenorthis (all Orthoidea) and Rongatrypa (Atrypoidea), as well as 10 new species: Bokotorthis minuta, Craniops pristinus, Chonetoidea enbektenensis, Dalmanella kotyrzhalica, Diambonioidea koknaiensis, Enbektenorthis molesta, Kassinella kasbalensis, Kozlowskites botobaicus, Leangella (Leangella) bakanasensis Phragmorthis eximia and Strophomena (Tetraphalerella) namasensis. Eleven ecological associations are recognized, which inhabited a spectrum of depths ranging from Benthic Assemblage Zone (BA) 1 to BA 5 depth ranges. Comparison of the faunas with the neighbouring Kazakh terranes is chiefly with the Chu-Ili, North Tien Shan and Boshchekul terranes since, although others have Late Ordovician faunas, their brachiopods are unknown or unrevised. There is much in common between the brachiopods of the Kazakh terranes, but individual faunas contain different species, many of which are endemic to one terrane. The Chingiz-Tarbagatai brachiopods show some similarities to contemporaneous faunas from the equatorial sectors of Gondwana, including Australia, and some with North China and South China, but have very little in common with those from Baltica and Laurentia. Thus the Chingiz-Tarbagatai Terrane was probably part of an archipelago which lay in a subequatorial position to the north-west of the Australasian sector of Gondwana and the adjacent South China continent in the Late Ordovician. http:zoobank.org/urn:lsid:zoobank.org:pub: C502E307-C67D-4216-869D-17D199812088 Keywords: Ordovician; Katian; Hirnantian; Brachiopoda; Kazakhstan; biogeography

Introduction Today’s Kazakhstan is made up of many Lower Palaeozoic terranes (Fig. 1); however, published opinions differ as to their boundaries, identities and their original positioning, both in relation to each other and also to the major neighbouring palaeocontinents of Gondwana, Baltica and Siberia, as well as the less substantial but still significant continents of North China and South China. Most of the Kazakh terranes are composite, and nearly all include island arcs which accreted to their margins at many different times. Their faunas, particularly the shallower-water benthos such as brachiopods, are important in terrane evaluation. The Chingiz-Tarbagatai Terrane was part of the eastern cluster of Kazakh terranes, and was probably close to the Boshchekul Terrane in the Early Palaeozoic (Popov et al. 2009). The Chingiz-Tarbagatai Terrane is composite, consisting of three or more units with possible Precambrian

*Corresponding author. Email: [email protected] Ó The Trustees of the Natural History Museum, London 2014

fragmentary cores, but chiefly comprising Lower Palaeozoic island arcs of oceanic origin. There is no agreement on the palaeogeography of the region at that time, as can be seen in the many differing published reconstructions, initially by Sengor & Natalin (1996) and Zonenshein et al. (2000), and most recently by Bazhenov et al. (2012) and Wilhem et al. (2012). However, faunal data can be vital in establishing the relative positions of such terranes, as reviewed globally for the Ordovician and Silurian by Fortey & Cocks (2003). Although many of the underlying Middle Ordovician (Darriwilian and Sandbian) brachiopods of the ChingizTarbagatai Terrane have been described by Popov (1975), Nazarov & Popov (1980) and Nikitin & Popov (1984), our previous knowledge of the brachiopods from the Katian and Hirnantian rocks which lie above them in the terrane has been inadequate for biogeographical assessment. The taxa published previously from those rocks,

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Figure 1. Outline map of Kazakhstan showing the Chingiz-Tarbagatai Terrane in relation to other terranes. 1, southern cluster of crustal terranes including Karatau Naryn, North Tien Shan and Chu-Ili. 2, eastern cluster of terranes including Atasu-Dzamshi microplate and Chingiz-Tarbagatai and Boshchekul composite terranes. 3, north-western cluster of terranes including Kalmykkol-Kokchetav unit and remnants of surrounding volcanic arcs (e.g. Ishim-Stepnyak, Ishkeolmes and Selety units). 4, boundaries of three major clusters of Kazakh terranes. 5, boundary of Chingiz-Tarbagatai composite terrane. 6, boundaries of major individual tectonic units within clusters. Mainly after S¸ eng€or & Natalin (1996) with emendations. The dashed box shows the area of Figure 3.

mainly by Borissiak (1955) and Klenina (1984), have required substantial revision, which is the chief purpose of this paper. It follows our study of contemporary Late Ordovician brachiopods from the neighbouring Chu-Ili Terrane (Popov & Cocks 2006; Popov et al. 2000, 2002). However, we have been hindered in our work by lack of access to material that we know exists, but which we have not been able to use, and thus this paper is based on perhaps a little more than half of the original collections which were originally made in the old Soviet era. We have not used the traditional Kazakh regional stage names for the Upper Ordovician, since they were established mainly in the Chu-Ili region and the Chingiz-Tarbagatai region formed a part of a separate terrane at the time.

Geological setting and key sections The stratigraphy of the Chingiz-Tarbagatai Terrane (Fig. 2) was summarized by Nikitin (1960, 1972) and Nikitin et al. (1991). The present paper is chiefly concerned with the Late Ordovician brachiopods from the

Akdombak and Taldyboi formations, and the main source of the specimens is the Upper Ordovician sections of the Bakanas and Taldyboi river basins (see Appendix). However, some small collections from other isolated localities across the Chingiz Range are also included (see Appendix), as are some specimens from the Kulunbulak Formation (Katian) of the Tarbagatai Range (Fig. 3), but the diverse Late Ordovician faunas of that region need further work. The geographical and geological positions of the many localities in older publications are often imprecise and poorly constrained. However, we have located most of those localities on ‘Google Earth’ satellite images, using old field records, sketch maps and (in a few cases) aerial photographs. The field notes made by O. P. Kovalevskii in 1964 and 1965 and by I. F. Nikitin have been particularly helpful. Although we understand that geographical coordinates (latitude and longitude) taken from ‘Google Earth’ may not be absolutely precise, they should serve as a good basis for future studies.

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Figure 2. Correlation chart of the Upper Ordovician sequences of selected tectonic units within Kazakhstan. Mainly after Nikitin (1991), with emendations.

Taldyboi and Namas rivers Outlines of the Ordovician geology and lithostratigraphy of the area are given by Klenina (1984) and Nikitin (1960, 1972, 1973). In the north-eastern part of the Chingiz-Tau Range the Upper Ordovician (uppermost Sandbian to middle Katian) deposits consist of the Taldyboi and Namas formations. The Taldyboi Formation contains abundant tabulate corals, brachiopods, bivalves, gastropods, cephalopods, trilobites and echinoderms; however, only part of the brachiopod fauna was described by Klenina (1984). In the type section between the Taldyboi and Namas rivers (Fig. 4), the Taldyboi Formation is up to 946 m thick and is thrust over undifferentiated Middle Cambrian siliceous siltstones (Nikitin 1960). The lower part of the Taldyboi Formation is best exposed on the eastern side of the River Namas (Fig. 3, Site 4; Figs 4, 5). The sequence (in ascending order with the thicknesses largely estimated) is as follows (after Nikitin 1972 and Klenina 1984): Unit 1. Pebbly, polymict, reddish lilac to greenish grey conglomerates with some beds of fine- to medium-grained polymict sandstones, up to 40 m thick.

Unit 2. Polymict calcareous sandstones intercalated with siltstones and gritstones 13 m thick with abundant brachiopods (Klenina 1984), including Austinella? grandis, Dulankarella aff. magna, Shlyginia namasensis, with unidentified gastropods and cephalopods. Unit 3. Dark grey algal limestones, 25 m. Unit 4. Greenish grey siltstones intercalated with fine grained sandstones, 47 m. Unit 5. Grey sandy limestones, 16 m. Unit 6. Coarse to fine-grained, greenish grey polymict sandstones, 15 m. Unit 7. Andesitic tuffs, 164 m. Unit 8. Greenish grey polymict sandstones with a few beds of siltstones and gritstones, 29 m. Unit 9. Dark grey siltstones and silty sandstones up to 33 m thick. The upper part of the Taldyboi Formation is best exposed on the western side of the Taldyboi River about 15 km west of the section above. There the Taldyboi Formation is also thrust onto undifferentiated Cambrian rocks (Figs 4, 5). The base of the Ordovician section is about 500 m upstream from the mouth of the Taldyboi River.

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Figure 3. Generalized map of the Chingiz and Tarbagatai regions showing the position of the brachiopod sites: 1, area c. 2 km northwest of Tentek grave (Locality 72); 2, Aschisu River, near the mouth of Egendybulak river (Localities 70 and 2133); 3, Taldyboi River; 4, Namas River (Locality 1858); 5, Kensai River (Locality 3142); 6, Akdombak Mountain and Kasbala River; 7, upper reaches of Bakanas River; 8, north side of Balkybek River (Locality 3126); 9, Kara-Bushir Mountain (Localities 1053, 1055); 10, Abak-Tiigen stream in Tarbagatai Range.

The sequence (in ascending order) is as follows (after Nikitin 1960): Unit TB1. Brownish grey, medium grained, cross-bedded arkosic sandstones, 20 m thick. Unit TB2. Greenish grey fine-grained bedded arkosic sandstones, 15 m. Unit TB3. Brownish grey poorly sorted sandstones with beds of polymict conglomerates, 25 m. Unit TB4. Greenish grey arkosic sandstones, 40 m. Unit TB5. Brown andesitic tuffs, 25 m. Unit TB6. Light, yellowish green, fine-grained volcanomict sandstones with some clasts of andesite volcanic rocks and tuffs, 80 m thick. Unit TB7. Dark grey and greenish grey argillites with a few limestone beds, 40 m. A few fossiliferous horizons (Figs 4, 5, Localities 282, 1830, 1831, 2423) contain a medium-diversity brachiopod fauna including Wrightiops nikitini, Ashinaorthis recta, Bokotorthis abayi, Schachriomonia parva and Sowerbyella papiliuncula. Unit TB8. Green siliceous siltstones, 80 m.

Unit TB9. Green calcareous and argillaceous siltstones intercalated with polymict medium-grained sandstones, 60 m (Figs 4, 5, Localities 1832, 1833). Brachiopods include Holmerglossa sp., Kassinella tchingisensis, Sowerbyella papiliuncula. Unit TB10. Greenish grey, poorly sorted polymict sandstones with a few limestone pebbles, 65 m. Unit TB11. Green, calcareous argillites with lens-like beds of dark grey bioclastic limestones, 50 m. Brachiopods include Phragmorthis sp. (Figs 4, 5, Locality 1834). Unit TB12. Greenish grey, poorly sorted coarse-grained polymict sandstones, 50 m. Unit TB13. Greenish grey siltstones with beds of calcareous siltstones, argillaceous limestones and finegrained sandstones in the lower part, 140 m. Unit TB14. Green argillaceous siltstones with a few beds of argillaceous limestones in the lower part, 85 m. Brachiopods include Paracraniops ellipticus, Acculina phyaliformis, Buminomena abayi, Mabella semiovalis, Rongatrypa instabilis, Phragmorthis sp., Sowerbyella

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Figure 4. Generalized geological map of the upper reaches of the Taldyboi River basin (Area 3 on Figure 3, modified from Nikitin 1960) showing position of fossil localities.

papiliuncula and Strophomena (Tetraphalerella) namasensis (Figs 4, 5, Localities 1835, 1836, 1838, 1841, 1858). The unit contains one of the earliest Kazakh rugose corals, Tchingizophyllum primitivum Sultanbekova. Unit TB15. Green, fine-grained sandstones intercalated with calcareous siltstones, 30 m. Unit TB16. Intercalated lilac and greenish grey siltstones and fine to medium-grained sandstones, 60 m, with abundant Ectenoglossa magna (Figs 4, 5, Locality 1843) and shell beds with Mabella semiovalis (Locality 1844) and Rongatrypa instabilis (Figs 4, 5, Locality 1842). The Taldyboi Formation is conformably overlain by pyroclastic rocks of the Namas Formation. A panoramic view of the section was given by Nikitin (1973, table 4).

The upper reaches of the Bakanas River basin A complete succession of Late Ordovician (Katian to Hirnantian) rocks is exposed continuously in the Mount Akdombak area between the Bailashkar and Alpeis rivers (Fig. 3, Sections 6, 7). The Akdombak Formation, whose stratigraphy was described by Bandaletov et al. (1965) and Klenina (1984), rests unconformably on volcanic rocks of probable Late Cambrian to Tremadocian age. Above a basal horizon of polymict sandstones and conglomerates, with pebbles of andesite, chert and limestones with archaeocyathids, the lower member (up to 400 m thick) consists mainly of limestones with abundant corals of the Agetolites mirabilis Fauna. The upper member (up to 1600 m thick) consists of siliciclastic rocks with

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Figure 5. Schematic stratigraphical section of the upper part of the Taldyboi Formation on the western side of the River Taldyboi showing the position of samples and brachiopod distribution. Geographical positions of the sections and fossil localities are shown on Figures 3 and 4.

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Late Ordovician brachiopods interbeds of limestones, tuffs and andesite lava flows. The Akdombak Formation is overlain disconformably by the Alpeis Formation of Llandovery age, which has a polymict conglomerate up to 17 m thick at its base, which is in turn succeeded conformably by the Zhumak Formation (Wenlock). Within the Akdombak Formation there are various well-preserved brachiopod faunas previously studied by Borissiak (1955), Klenina (1984), and some pentamerides by Sapelnikov & Rukavishnikova (1975). Four faunas of successive ages from Early Katian to Hirnantian were collected by M. A. Borrisiak, O. P. Kovalevskii, I. M. Kolobova and L. E. Popov between 1956 and 1985, and these form the chief topic of this paper. The best studied Ordovician–Silurian boundary sequence in the Chingiz Range is in the upper reaches of the River Bakanas in the Mount Akdombak area (Figs 3, 6–8). Descriptions of the section and faunal logs are given by Bandaletov et al. (1965) and Nikitin (1972). The Upper Ordovician and Llandovery rocks in the area contain diverse faunas, including tabulate and rugose corals (Sultanbekova 1986), bivalves, gastropods, cephalopods

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(Barskov 1972), brachiopods, trilobites, ostracods, echinoderms and graptolites; however, only some of the brachiopods were described by Klenina (1984). The sequence of the Akdombak Formation in the type area near Mount Akdombak is, in ascending order (Bandaletov et al. 1965): Akdombak Formation, Lower (carbonate) Member (Middle Katian) Unit 1. Poorly sorted, polymict conglomerates with sandy matrix and sandstones, up to 25 m thick. The included pebbles are mostly andesites, quartzites and jaspers. Unit 2. Grey argillaceous limestones, up to 30 m, with trilobites including Remopleurides, Illaenus and unidentified cheirurids and asaphids. Unit 3. Grey to dark grey limestones, up to 40 m thick, with abundant tabulate corals including Agetolites multitabulatus Lin, Catenipora subparallela Kovalevskii, Reushia sp., Propora sp. and Plasmoporella kasachstanica Bondarenko. Unit 4. Dark grey, thick-bedded limestones, up to 350 m thick, with the rare trilobite Remopleurides and the brachiopods Monomerella sp. (Figs 6, 7, Locality 7963)

Figure 6. Geological map of the area around Akdombak Mountain (modified after Bandaletov et al. 1965) in the centre of the ChingizTarbagatai Terrane showing position of fossil localities.

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Figure 7. Schematic stratigraphical sections of the Akdombak Formation in the Mount Akdombak area (Akdombak section) and the upper reaches of the Bakanas River basin (Tolen Section) showing the position of samples. Geographical position of the sections and fossil localities are shown on Figures 3 and 6.

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Late Ordovician brachiopods and Ilistrophina? sp., bivalves and gastropods (Figs 6, 7, Locality 79149). Unit 5. Grey to dark grey limestones up to 90 m thick, with the corals Agetolites mirabilis Sokolov, Palaeofavosites acerbus Kovalevskii, Calapoecia aff. anticostiensis Billings, Plasmoporella convexotabulata Kiaer, Plasmoporella crassa Kovalevskii, Sarcinula terbagataica Kovalevskii and Stelliporella sp., and the cephalopods Beloitoceras nikitini Barskov and Oncoceras cf. delicatum Flower. Unit 6. Grey nodular argillaceous limestones up to 50 m thick, with the trilobites Ceraurinella, Encrinuroides and Illaenus, and brachiopods Sowerbyella (S.) akdombakensis and Schachriomonia parva (Figs 6, 7, Localities 601, 1859, 7967). Eastwards of the described section, where the Lower Member of the Akdombak Formation is exposed along the northern side of the River Bakanas, a more diverse assemblage was recovered by Kovalevskii and Popov from Unit 6 (Figs 7, 8, Localities 593 and 7975), which includes the rugose coral Grewingkia contexta Neuman, the trilobite Remopleurides, the brachiopods Anoptambonites sp., Bellimurina sp., Dulankarella sp., Mabella sp., Shlyginia sp., Bokotorthis minuta, Phaceloorthis? sp., Phragmorthis eximia, Qilianotryma sp. and Schachriomonia parva, and the algae Contexta spirata Gnilovskaya, Sinuatoporella traulliformis Gnilovskaya and Vermiporella tuberiformis Gnilovskaya. Akdombak Formation Upper Member (Late Katian to Hirnantian) Unit 7. Greyish green pebbly volcanomict conglomerates with a matrix of coarse-grained, tuffaceous sandstone, up to 50 m thick.

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Unit 8. Greyish green siltstones and sandstones 65 m thick, with Dalmanella kotyrzhalica; Diambonioidea koknaiensis, Foliomena folium, Kassinella kasbalensis and Leangella (L.) bakanasensis (Localities 2083, 2084). Unit 9. Greenish grey sandstones with a few siltstone interbeds, up to 330 m thick. Unit 10. Greyish green and brownish red silty argillites interbedded with silty sandstones, 180 m thick, with the graptolites Dicellograptus cf. pumilus Lapworth, Climacograptus cf. supernus Elles & Wood, Rectograptus truncatus Lapworth and Rectograptus cf. giganteus Keller, the trilobites Ampyxinella, Microparia, Remopleurides and Nankinolithus aff. granulatus (Wahlenberg), and the brachiopods Dalmanella kotyrzhalica and Kassinella kasbalensis (Figs 6, 7, Localities 45, 256). Unit 11. Intercalated greyish green and brownish red argillites and siltstones up to 320 m thick. Unit 12. Greyish green silty argillites, 10 m thick. Unit 13. Polymict conglomerates, 15 m thick with pebbles of siltstones, sandstones, limestones and volcanic rocks. Limestone pebbles contain the tabulate corals Agetolites sp., Palaeofavosites sp. and Plasmoporella cf. convexotabilata Kiaer. Another important section, the Tolen section, is exposed between the Tolen and Alpeis rivers about 3 km south-east of Enbekten village and 11 km east of Akdombak Mountain. The Upper Ordovician and Silurian rocks in the area dip westwards at 28–30 . The sequence (in ascending order) is as follows (after O. P. Kovalevskii MS): Unit T1. Bluish grey bedded siltstones, 110 m, with Anoptambonites sp., Bokotorthis cf. plicadua, Christiania

Figure 8. Schematic geographical map of the upper reaches of the River Bakanas showing the positions of fossil localities.

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aff. proclivis, Dulankarella? sp., Holtedahlina aff. orientalis, Mabella sp., Phragmorthis sp., Shlyginia sp. (Figs 7, 8, Locality 8506), the trilobites Dulanaspis, Illaenus, Remopleurides and Sphaerexochus, and columnals of the echinoderms Babanicrinus tuberosus Stulakina, Bystrowicrinus and Siderocrinus. Unit T2. Reddish grey pebbly conglomerates in a matrix of coarse-grained sandstone, up to 320 m. In the middle part of the unit, the size of pebbles increases up to 10–15 cm in diameter. Unit T3. Grey, coarse- to medium-grained sandstones, 25 m. Unit T4. Greenish grey gritstones with horizons of pebbly conglomerates, up to 69 m. Unit T5. Greenish grey calcareous sandstones, siltstones and limestones, 40 m, with the corals Agetolites cf. mirabilis Sokolov, Heliolites cf. parvulus Kovalevskii and Plasmoporella cf. convexotabulata Kjaer, the brachiopods Christiania aff. proclivis, Olgambonites? sp., Platymena sp., Sowerbyella (S.) akdombakensis, Testaprica ajaguzensis and Schachriomonia parva (Figs 7, 8, Localities 669, 3114, 3115), and columnals of the echinoderms Formalicrinus minimus Stukalina, Bystrowicrinus quinquilobatus Yeltysheva, Cuboidecrinus cuboides Stukalina, Babanicrinus and Ristnacrinus. Unit T6. Andesite lava flows with horizons of andesitic tuffs, 25 m. Unit T7. Reddish grey andesitic tuff and andesite volcanic mass flows, 300 m. Unit T8. Reddish grey coarse-grained sandstones, 80 m. Unit T9. Brownish grey and greenish grey calcareous sandstones with irregular beds and lenses of sandy limestones, 40 m, with the rugose corals Palaeophyllum fasciculatum Kutorga, Tchingizophyllum tarbagataicum Sultanbekova, the tabulate corals Agetolites sp., Hemiagetolites ramosus Kovalevskii, Catenipora inordinata Kovalevskii, Plasmoporella cf. crassiformis Kovalevskii, Reushia minima Kovalevskii, Heliolites tolenensis Kovalevskii, Saryarkia cf. bandaletovi Kovalevskii, the brachiopods Holorhynchus giganteus latisulcifer, Luhaia? bakanasensis, Rostricellula sp., Sowerbyella sp. (Figs 7, 8, Localities N-511, 1756), the trilobites Illaenus and Remopleurides, and the echinoderm columnals Apertocrinus, Bystrowicrinus bellus Stukalina, Cuboidecrinus cuboides Stukalina and Malovicrinus (Locality 1756). Unit T10. Bluish grey and greenish grey sandstones and siltstones, 55 m, with the trilobites Illaenus, Pliomerina and Remopleurides, and numerous echinoderm columnals, including Babanocrinus tuberculatus Stukalina, Bystrowicrinus bellus Stukalina, Cuboidecrinus cuboides Stukalina, Fascicrinus subflabelliformis Stukalina, Formallocrinus minimus Stukalina, Ristnakrinus kulunbulakensis Stukalina and Spinicrinus pectenatus Stukalina. Unit T11. Greenish grey calcareous sandstones with lenses of grey limestones, 25 m. The uppermost part of

the unit contains accumulations of the brachiopod Alpeis tolenensis (Figs 7, 8, Localities 1766, 3088). Unit T12. Greyish lilac sandstones and siltstones with horizons of greyish green and bluish green siltstones. A bed of bluish green siltstones at about 30 m from the base of the unit (Figs 7, 8, Localities 43, 2062, 2080 and 2081) contains numerous brachiopods: Kozlovskites botobaicus, Chonetoidea enbektenensis, Cliftonia sp., Eostropheodonta sp., Katastrophomena sp., Leptaena enucleata, Craniops pristina; and the trilobite Mucronaspis. The Ordovician–Silurian boundary in the Akdombak Mountain area can be placed provisionally at the top of the conglomerate bed (Unit 13), which was probably deposited during the period of maximum eustatic lowstand in the Hirnantian. The low-diversity faunal assemblage from the overlying limestone (Unit 14 of the Akdombak section) contains Eospirifer, which is unknown in the Ordovician apart from in South China (Rong et al. 1994; Modzalevskaya & Popov 1995). The underlying conglomerates and siltstones (Units 12–13) are barren; however, the rocks underlying the Silurian in the Tolen Section (Unit T12) contain a distinctive faunal assemblage, probably of Hirnantian age and consisting mostly of genera alien to the earlier Kazakh fauna, such as the brachiopods Coolinia, Eostropheodonta, Katastrophomena and Leptaena, and the trilobite Mucronaspis, suggesting the immigration of cooler-water faunas from temperate-latitude Gondwana. However, that fauna lacks many typical elements of the Hirnantian brachiopod assemblage, including Hirnantia itself.

Previous work and age of the fauna Borissiak (1955, 1972a, b) described a number of the Late Ordovician taxa, mostly in open nomenclature, but (with a few exceptions) information on their geological and stratigraphical positions is very general and their taxonomic affiliations questionable. Monomerella sp. (Borissiak 1955, p. 30) is probably conspecific with the shells that occur in the lower part of the Akdombak Formation in the Akdombak area. Borissiak’s specimens were collected in 1948 by O. I. Nekrasova in the upper reaches of Sarybulak River (Borissiak 1955, p. 76, Locality 187, at approximately 48 550 N, 79 550 E). No details of the lithostratigraphy are available, but it is probably the limestone unit in the lower part of the Akdombak Formation. The specimens assigned by Borissiak (1955, p. 32) to Hebertella cf. borealis are poorly preserved; however, they are neither congeneric nor conspecific with the taxon established by Billings (1863), and they are derived not from the Chingiz Range, but from the eastern side of the Turgai depression more than 1000 km to the west, and thus are not revised here. Doleroides sp. of Borissiak (1955, p. 32) from the northern slope of Mount Kara-Bushir is the same as Alpeis tolenensis (Borissiak, 1972a) from the upper part of the Akdombak Formation of the Tolen River Section. The form identified as Cyclocoelia

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Late Ordovician brachiopods cf. sordida-multiplicata Foerste, 1910 by Borissiak (1955, p. 34) from the Upper Ordovician of Mount Kara-Bushir, is probably an early atrypide assignable to Rongatrypa. The taxonomic affiliation of Pionodema sp. (Borissiak, 1955, p. 41) is uncertain, and its age and geographical position cannot be determined with any degree of certainty. Borissiak (1955, p. 44) was the first to record Holorhynchus cf. giganteus from the upper reaches of Bakanas River (Tolen section). Specimens from Mount KaraBushir assigned by Borissiak (1955) to Sowerbyella sericea (Sowerby, 1839) and Strophomena ajaguzensis are revised here as Sowerbyella (S.) intricata and Testaprica ajaguzensis. Borissiak (1972a, b) and Goriansky (1972) published descriptions of new taxa (revised below) from the Upper Ordovician of the Chingiz Range, including Mimella (¼ Alpeis) tolenensis Borissiak, 1972a, Sowerbyella (S.) papiliuncula Borissiak, 1972b, Ectenoglossa magna Goriansky, 1972, Paracraniops ellipticus Goriansky, 1972 and Paracraniops (¼ Wrightiops) nikitini Goriansky, 1972. Klenina (1984) published the most comprehensive study on the Upper Ordovician (mostly Katian) brachiopods, which are mostly reviewed below. However she also described taxa not represented in our studied collection and whose taxonomic affiliation is uncertain. Amongst the nine species described from the Abai Formation (which she identified as of Llanvirn age) of the Ordotas Mountains, part of the Chingiz Terrane, the generic affiliations of ‘Aporthophyla’ ordensis, ‘Leptellina’ infrequens, ‘Oepikina’ tojoni karaadirensis and ‘Sowerbyella’ nativa are unknown because their interiors are inadequate; Hesperorthis kaaradirensis may represent a species of Paralenorthis; and Bicuspina rukavishnikovae was redescribed and discussed by Popov et al. (2002). ‘Sowerbyella’ plana is a junior objective homonym of Sowerbyella plana R~ o~ omusoks, 1959. Shells attributed by Klenina (1984, p. 103) to Rhynchotrema increbescens minnessotensis (Sardeson, 1892) are rhynchonellide, but in the absence of information on their interiors, their genus and species must remain doubtful. The age of the fauna from the Abai Formation is most probably Sandbian, since it includes Bicuspina rukavishnikovae (as in the Anderken Formation of the Chu-Ili Range) and also rhynchonellides, which are unknown in the Darriwilian of Kazakhstan. Amongst species documented from the lowermost (presumably Sandbian) part of the Taldyboi Formation, which are not represented in the present collection, the affinity of Austinella grandis Klenina, 1984 was discussed by Popov et al. (2002). Dulankarella aff. magna Rukavishnikova, 1956 is known only from exteriors, which makes generic affiliation of the shells uncertain, D. namasensis and D. subquadrata came from the same locality in the lower part of the Taldyboi Formation and their dorsal and ventral interiors suggest attribution to Shlyginia; both can be included within Shlyginia namasensis. Christiania taldyboyensis Klenina, 1984, from the upper part of the Taldyboi Formation,

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does not show any sign of its attribution to that genus or to any strophomenoid and is here considered a nomen dubium. Specimens assigned to Schizophorella aff. kasachstanica Rukavishnikova, 1956, by Klenina (1984, p. 49) probably represent an atrypide, perhaps Rongatrypa, and may be conspecific with the shells identified by Klenina (1984, p. 108) as Rhynchotrema aff. rudis Rukavishnikova, 1956. The shells described by Klenina (1984, p. 53) as Dalmanella pulchra Borissiak MS represent at least two orthid species of uncertain affinities and the taxon is considered here as a nomen dubium, especially because the selected holotype IGNA 411/75 is an incomplete external mould of conjoined valves, which excludes any possibility of positive generic identification. Klenina must be considered as the author of the binomen. The generic affiliation of Paucicrura tschinghisensis Klenina, 1984, is uncertain and requires revision. Authorship and generic affiliation of Dedzetina antecendens Borissiak (MS) was discussed by Nikitin et al. (2006). The holotype of the species represents a pair of conjoined valves and it is difficult to be confident that it is the same species as ventral and dorsal internal moulds attributed to it. Conjoined valves of Phragmorthis eximia sp. nov. described in the present paper look somewhat similar and they were probably sampled from the same horizon as the specimens described and illustrated by Klenina (1984, p. 57, pl. 4, Figs 1–3). The taxonomic affiliations of Cyclospira? elegantula Rozman, 1964, and Rhynchotrema otarica Rukavishnikova, 1956, are also questionable, since they are not supported by sufficient information on the interiors. Sowerbyella (Viruella) praestans Klenina, 1984, came from the Baban Formation, outside the study areas and probably from a different terrane, but appears to be a valid species of Rugosowerbyella. Sapelnikov & Rukavishnikova (1975) described and illustrated five pentameride taxa from the Upper Ordovician of the Chingiz Range. Amongst them, Holorhynchus giganteus giganteus Kiaer, 1902, and Holorhynchus giganteus latisulcifer are synonymous, whereas Antigaleatella (¼ Brevilamnulella) laevis and Galeatellina kajnarensis are not represented in our collection. The latter three species occur in several localities (River Bolga north-west of Akbulak village, Mizek and Otyzbes mountains in the Chingiz Range) in the upper part of the Akdombak Formation (Holorhynchus giganteus Beds) which are situated north or north-west of our study areas, but their geographical positions are poorly constrained and any associated faunas unknown.

Brachiopod associations Most of the specimens used in the present study were assembled by many different people through a prolonged period, mostly for routine biostratigraphy, and thus their detailed quantitative biofacies analysis is difficult and subjective. Nevertheless, several natural brachiopod associations are recognizable in the samples, even though

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Late Ordovician brachiopod associations show significant variations in abundance, proportions and taxonomic diversity due to the complicated palaeogeographical characteristics of volcanic island arc settings. The inferred depth relationships between the associations cannot be supported by onshore–offshore transects and are mainly based on analogies with similar associations in other parts of Kazakhstan and beyond.

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Ectenoglossa? magna Association This is a typical monotaxic lingulide association dominated by Ectenoglossa? magna and is confined to the violet-grey, fine-grained sandstones in the uppermost part of the Taldyboi Formation (Unit TB16, Locality 1843). No detailed sedimentological documentation is available to reconstruct its environment with certainty, but it was probably a nearshore shoal complex of Benthic Assemblage Zone (BA) 1. Similar lingulide associations are widespread through the Kazakh terranes, including ChuIli, North Tien Shan and Chingiz-Tarbagatai. Environments characteristic of the lingulide associations from Chu-Ili were discussed by Popov et al. (2002, 2007).

Rongatrypa instabilis Association This is monotaxic, probably of BA 2, dominated by the single atrypide Rongatrypa instabilis and is preserved in shell accumulations within the fine-grained sandstones in the uppermost part of the Taldyboi Formation at Taldyboi (Locality 1842) and Kensai (Locality 3142). Sporadic cooccurrences of the lingulide Ectenoglossa? magna in association with Rongatrypa suggest that this association inhabited a turbulent nearshore shallow marine environment in relative proximity to the area occupied by the lingulide associations, and thus this association can be considered as vicariant to the Late Ordovician to Silurian rhynchonellid-dominated associations nearshore. There is a medium-diversity Altaethyrella-Rongatrypa Association in the Early Katian of the Chu-Ili Terrane (Popov et al. 2000), which is also confined to BA 2; however, it does not appear to be analogous to the Rongatrypa instabilis Association.

Mabella semiovalis Association This is another monotaxic association and is dominated by a single plectambonitoid species, although Paracraniops ellipticus may also occur as a minor component. The Mabella semiovalis Association is known from two localities (1841 and 1844) in the uppermost part of the Taldyboi Formation of the Taldyboi section (Unit TB16). Unlike monotaxic lingulide and atrypid associations in this unit, it shows preference for fine clastic sediments, mainly finegrained silty sandstones and silts. Perhaps all three are opportunistic associations in areas of high environmental stress related to the considerable volcanic activity.

Bokotorthis abayi Association This is a medium-diversity association probably of BA 2 or 3, characteristic of silty bottoms within an offshore, low energy, shallow marine environment, and is based on samples from four localities (282, 1830, 1831 and 2423). Bokotorthis abayi is the abundant taxon, and also common are Ashinaorthis recta, Schachriomonia parva and Sowerbyella (S.) papiliuncula. The craniopside Wrightiops nikitini is locally abundant, but proportions of that taxon vary greatly between localities. No similar associations are known from other Kazakh terranes.

Sowerbyella akdombakensis–Schachriomonia parva Association This is a low-diversity brachiopod–tabulate coral association (BA 2), known from Localities 601, 1859 and 7967 in the upper part of the limestone unit (Unit 6). Sowerbyella (S.) akdombakensis is the dominant taxon. Sowerbyella-dominated brachiopod associations are also widespread on clastic shallow shelves in the Chu-Ili, NorthTien Shan and Karatau-Naryn terranes (Misius 1986; Popov et al. 2000, 2002), but there are no other records of their association with abundant faunas of tabulate corals.

Holorhynchus Association The Holorhynchus Fauna has been discussed repeatedly in publications on palaeontology and biostratigraphy of the Upper Ordovician of Kazakhstan (Apollonov et al. 1980; Bandaletov et al. 1965; Nikitin 1972; Sapelnikov & Rukavishnikova 1975), but there is little known about its taxonomic diversity, trophic structure and associated benthic organisms. In Chingiz the Holorhynchus Association often co-occurs with the Agetolites tabulate coral Association in the Late Katian part of the Akdombak Formation (Localities N-511, 1756). Associated brachiopod taxa are Alpeis tolenensis, Luhaia? bakanasensis and Rongatrypa sp. By analogy with Silurian large pentameride-dominated associations, it can be assigned to BA 3, but our collection is too small for more detailed characterization of the association.

Kassinella Association This is an oligotaxic association, probably of BA 4, from the single Locality 1833 in the mid part of the Taldyboi Formation in the Taldyboi section (Unit TB9). It comprises Kassinella tchingisensis and Holmerglossa sp., which inhabited a fine clastic silty bottom offshore.

Dalmanella kotyrzhalica–Nankinolithus Association This is an oligotaxic to monotaxic association, corresponding to BA 5, and is known from several localities (45, 256, 2084, 85244) mainly in the Latest Katian part of

Late Ordovician brachiopods the Akdombak Formation. The Dalmanella kotyrzhalica Association often occurs in black silty argillites and is invariably dominated by the index-species, often with the trilobite Nankinolithus. Kassinella kasbalensis is occasionally present as a minor component. Dalmanella is unknown in the Kazakh faunas for most of the Late Ordovician, and after immigration to the Chingiz Terrane it occupied marginal oxygen-deficient environments, which represents an unusual life strategy by comparison with other species of the genus.

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Foliomena Association This is a low-diversity association, probably BA 4 or 5, characteristic of a clastic silty bottom offshore. It is known only from Locality 2083 in the middle part of the Akdombak Formation. Characteristic taxa include Diambonioidea koknaiensis, Foliomena folium and Kassinella kasbalensis. It is similar to the Early Sandbian Foliomena Association from the Miaopo Formation of South China (Rong et al. 1999), but the diversity is lower. We have not recognized the high diversity Foliomena Association of Klenina (1984, p. 124) in the upper Akdombak Formation, which Rong et al. (1999) regarded as anomalous, and it appears that Klenina grouped together genera from almost 400 m of rocks which do not represent a single brachiopod association, especially since many of the listed taxa, including Foliomena itself, were not included in her monograph.

Chonetoidea–Kozlowskites Association This is a medium-diversity association, probably representing BA 4, and is questionably dated as Hirnantian. It is confined to the bed of bluish green siltstones of Unit T12 in the uppermost part of the Akdombak Formation (Localities 43, 2062, 2080, 2081) in the Tolen Section. Chonetoidea enbektenensis and Kozlowskites botobaicus are the most common taxa, and others include Cliftonia sp., Craniops pristinus, Dalmanella sp., Eostropheodonta sp., Epitomyonia sp., Katastrophomena sp., Leptaena (L.) enucleata and Trematis aff. taljaardi. The Hirnantian age of the fauna is inferred from the trilobite Mucronaspis sp., which is confined to the Hirnantian in Kazakhstan (Apollonov et al. 1980). The same is true for Eostropheodonta, which is also a common component of the Hirnantia Association in Chu-Ili (Nikitin et al. 1980), although the genus also occurs in the Late Katian elsewhere (Cocks 2014). Cliftonia, Kozlowskites, Leptaena and Dalmanella are also alien taxa to most of the Kazakh Ordovician faunas, and their first occurrence in Chu-Ili is in the uppermost Katian, slightly below the base of the Normalograptus extraordinarius Biozone (Apollonov et al. 1980). A significant proportion of the rhynchonelliform specimens are conjoined valves, suggesting that the shells were preserved at least close to the area of their original habitat. No

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detailed sedimentological documentation is available for the transitional Ordovician–Silurian beds of the Tolen and Akdombak sections.

Palaeogeographical implications The biogeographical patterns of benthic faunas across Kazakhstan suggest that throughout the Middle to Late Ordovician a number of terranes (which were much later incorporated into the Central Asian Orogenic Belt) converged to form an archipelago that extended along the Equator, probably west and north-west of the Australasian sector of Gondwana. This inferred location of the Kazakh terranes and island arcs is supported by clear signals from brachiopod and trilobite taxa, suggesting strong links with the contemporaneous faunas of Australia and South China (Fortey & Cocks 2003; Nikitin et al. 2006; Popov et al. 2009; Percival et al. 2011), which were close to each other in the Late Ordovician (Cocks & Torsvik 2013). There are some hints from palaeomagnetic data that the Kazakh terranes were close to the palaeoequator in the Ordovician, but no precise palaeolatitudes have yet been deduced for them, as reviewed by Bazhenov et al. (2012). Previous biogeographical assessments of the Late Ordovician brachiopod faunas from the Chingiz-Tarbagatai Terrane were made on incomplete data largely derived from earlier publications. The present paper, based on extensive new collections as well as a revised analysis of published data, establishes firm support to the general Late Ordovician faunal links of the Chingiz-Tarbagatai Terrane with north-east Gondwana (Australasia), but also reveals new faunal data important for the better understanding of the palaeogeography and relative position of the Kazakh island arcs and microcontinents. It seems likely that the Australasian sector of Gondwana might have been a major source for the pioneering brachiopod faunas which populated the Kazakh terranes in the Darriwilian to Early Sandbian. A cluster analysis of the Middle Ordovician (Darriwilian and Sandbian) periGondwanan faunas by Percival et al. (2011, fig. 2A) demonstrated that the Kazakh faunas form a single cluster with contemporaneous Australasian faunas, whereas the South China faunas clustered separately. A similar pattern was demonstrated for the Darriwilian trilobites, and in South China the shallow-shelf asaphid biofacies of that time were dominated by genera of the Subfamily Nobiliasaphinae and especially Liomegalaspides (Turvey 2005). Study of asaphid biofacies from the Chu-Ili Terrane of Kazakhstan reveals two distinctive genera Damiraspis and Farasaphus, which also occur in the Sibumasu and Australasian sectors of Gondwana (e.g. Thailand, New South Wales) but are also reported from Argentina (Ghobadi-Pour et al. 2009; Ghobadi-Pour et al. 2011a). Zhou & Zhen (2009) noted that Eokosovopeltis, one of the index taxa for the Eokosovopeltis–Pliomerina Province of Webby et al. (2000), was present in the Sandbian of North

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China, the Australasian sector of Gondwana and the Kazakh terranes, but did not appear in South China until the Katian. There are some distinctive brachiopod genera, for example, Mabella, Shlyginia and Testaprica, which occur in Chingiz-Tarbagatai and New South Wales, but not in South China. The Katian fauna of the Chingiz-Tarbagatai Terrane described here shows a higher degree of endemism than previously suspected; in particular, the genera Alpeis, Ashinaorthis, Buminomena and Wrightiops and the subfamily Alpeisinae are endemic to the terrane. In contrast, brachiopods such as Glyptomenoides, Metambonites, Nikitinamena, Ogmoplecia, Sortanella, Synambonites and Weberorthis, which are quite common in the Chu-Ili Terrane (and Metambonites and Synambonites also occur in South China), but are not known from the Chingiz-Tarbagatai Terrane. To summarize, the biogeographical data suggest that the Kazakh terrane archipelago was populated by faunas with strong links to equatorial Gondwana (the Australasian sector), but also that in the Middle to Late Ordovician they occupied low latitude intraoceanic locations in the tropical oceans, well isolated from Baltica and Siberia.

Systematic palaeontology Specimens are deposited in NHMUK: Natural History Museum, London, UK prefixed BC; NMW: National Museum of Wales, Cardiff, UK; IGNA: Institute of Geological Sciences, Almaty, Kazakhstan; and CNIGR: the Central Geological Scientific Research and Exploration Museum, St Petersburg, Russia. Dimensions are given in mm in brackets after some specimen numbers: W, L, T, maximum width, length, thickness of the shell; Lv, Ld, maximum length of ventral and dorsal valve; L/W, length/width ratio; Iw, Il maximum width and length of interarea; VMl, VMw, ventral muscle platform length and width (in craniopsides); Bl, Bw, brachiophore length and width; Ml, Mw length and width of muscle field; Sl, median septum length. Order Lingulida Waagen, 1885 Superfamily Linguloidea Menke, 1828 Family Obolidae King, 1846 Subfamily Glossellininae Cooper, 1956 Genus Ectenoglossa Sinclair, 1945 Type species. Lingula lesueueri Rouault, 1850, from the Floian of Normandy, France. Ectenoglossa? magna Goriansky, 1972 (Figs 9A–E, 10A) 1972 Ectenoglossa magna Goriansky: 169, pl. 43, figs 1–3.

Holotype. CNIGR 1/9563 (Fig. 9D), ventral valve, upper part of the Taldyboi Formation (Lower Katian), River Taldyboi, Chingiz Range. Paratypes. CNIGR 2/9563, dorsal valve (Fig. 9C); CNIGR 3/9563, ventral valve. Other material. Locality 70 (lower Katian), one ventral valve, (NMW 2001.38G.2 (Lv 13.7, W 6.5; Fig. 10A); Locality 1842 (Lower Katian), one ventral valve, NMW 2001.38G.1 (Fig. 9A), one dorsal valve, NMW 2001.38G.793 (Fig. 9E). Remarks. This species is relatively common in the uppermost part of the Taldyboi Formation; however, including paratypes, only a few specimens have been available for study. The generic position of the species is poorly supported because of the lack of evidence of two short, subparallel ridges in the posterior part of the ventral valve, which are diagnostic for the genus. Genus Holmerglossa gen. nov. Type species. Pseudolingula spatula Williams, 1974, from the Weston Formation (Darriwilian) of Shropshire, England. Derivation of name. To honour Lars Holmer for his outstanding work on early brachiopods. Diagnosis. Glosellininae with elongate, parallel-sided dorsibiconvex to subequally biconvex shell ornamented with fine filae. Ventral valve with rudimentary pseudointerarea divided by a pedicle groove into two striated propareas elevated above the valve floor. Ventral interior with low anterior muscle platforms, bordered anteriorly by a rim. Dorsal interior with a strong median septum bisecting all the visceral area and extending anteriorly well beyond mid-valve. Umbonal muscle scars paired symmetrically placed in both valves. Large central muscle scars in mid dorsal valve. Remarks. Williams (1974) correctly assigned the Weston species to the subfamily Glossellinae; however, the specimens are not Pseudolingula, but a different glossellinine genus which is here formally named. Holmerglossa differs from most of the other genera assigned to the subfamily Glossellinae, and in particular from Ectenoglossa Sinclair, 1945, Libyaeglossa Havlıcek in Havlıcek & Massa, 1973 and Tunisiglossa Havlıcek in Massa et al., 1977, in having a strong median ridge bisecting the entire dorsal visceral area and two ventral anterior muscle platforms. Unlike Libyaeglossa it has only a rudimentary ventral pseudointerarea. Plectoglossa Cooper, 1956 is another externally similar genus, but it differs in having a fold which bisects medially the ventral interarea. The interiors of both valves in Plectoglossa itself are yet unknown, which makes further comparison difficult.

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Figure 9. A–E, Ectenoglossa? magna Goriansky, 1972, Katian, Taldyboi Formation, River Taldyboi; A, NMW 2001.38G.2, ventral exterior, Locality 1842; B, Acc. CNIGR 9563, ventral exterior, Locality 1843; C, CNIGR 2/9563, exfoliated dorsal interior showing paired umbonal muscle scar, Locality 1843; D, CNIGR 1/9563, holotype, ventral exterior, Locality 1843; E, NMW 2001.38G.793, dorsal exterior, Locality 1842. F–I, Paracraniops ellipticus Goriansky, 1972, Katian, Taldyboi Formation, Locality 1841, River Taldyboi; F, CNIGR 16/9563, ventral internal mould; G, CNIGR 13/9563, holotype, latex cast of ventral exterior; H, CNIGR 15/9563, dorsal internal mould; I, CNIGR 14/9563, dorsal internal mould. Scale bars 2 mm.

It is probable that at least some of the species assigned by Sinclair (1945) and Cooper (1956) to Pseudolingula may in reality belong to Holmerglossa; however, pending a substantial revision, their generic attribution remains uncertain. Holmerglossa sp. (Fig. 10B–D)

1974), from the Weston Beds (Darriwilian) of Shropshire, and are congeneric. However, there is not enough material to erect a new species from the Chingiz Terrane. Superfamily Discinoidea Grey, 1840 Family Trematidae Schuchert, 1893 Genus Trematis Sharpe, 1848

Material. Taldyboi Formation, Locality 1833, external mould of conjoined valves BC 60211 (L 4.4, Wd 3.5) (Fig. 10B); one ventral external mould, NMW2001.38G.788, one dorsal valve, NMW2001.38G.789, dorsal internal moulds BC 60212 (Fig. 10D), four dorsal external moulds BC 60210 (Fig. 10C), NMW2001.38G.790–792.

Type species. Orbicula terminalis Emmons, 1842, from the Trenton Group (Katian) of New York, USA.

Remarks. In having a smooth shell with a strong dorsal median septum and in the absence of a dorsal interarea, these shells resemble Holmerglossa spatula (Williams,

Material. Akdombak Formation (Hirnantian), Locality 2080, BC 60213 (Fig. 10E, F), conjoined valves (L 21.3, W 26.5).

Trematis aff. taljaardi Rowell in Cocks et al., 1970 (Fig. 10E, F)

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Late Ordovician brachiopods Remarks. A single relatively large distorted specimen in our collection is characterized by a finely ornamented shell, with bifurcating ribs varying from 18 to 20 per 3 mm, and interspaces between ribs bearing rows of fine, hemispherical pits about 120 to 130 mm across. The specimen has a slightly depressed umbonal area with a triangular pedicle notch and the ventral umbo is at about one-fifth sagittal length from the posterior margin. It is comparable in overall size, shape and size of the pedicle opening, position of the ventral umbo, and the characters of the pitted microornament to Trematis taljaardi Rowell in Cocks et al., 1970, from the Hirnantian Cedarberg Formation of South Africa, but has slightly finer radial ornament (18–20 ribs per 3 mm instead of 12–16 in T. taljaardi). Trematis norvegica Cocks, 1982, from the Hirnantian Langøyene Formation of the Oslo Region, Norway, is another similar and approximately contemporaneous taxon; however, it is characterized by significantly coarser pitting and radial ornament, and it is also much larger. Order Craniopsida Goriansky & Popov, 1985 Superfamily Craniopsoidea Williams, 1963 Family Craniopsidae Williams, 1963 Genus Craniops Hall, 1859 Type species. Orbicula squamiformis Hall, 1843, from the Niagara Group of New York, USA. Craniops pristina sp. nov. (Figs 10I–P, 11G, I) Diagnosis. Shell small for genus with weakly defined cicatrix area, up to 14 regular, evenly distributed, thin growth lamellae and sagittal dorsal valve profile steeply sloping from the umbo to the posterior margin. Derivation of name. After Latin pristinus – former, previous. Holotype. NMW2001.38G.418 (Ld 3.4, W 2.6, Vl 2.1, Vw 1.3; Fig. 10M) dorsal internal mould; upper part of Akdombak Formation (Hirnantian?), Locality 43, River Tolen, Chingiz Range. Paratypes. Locality 43, one dorsal internal mould, NMW2001.38G.417 (Ld 4.1, W 3.8, Vl 2.7, Vw 1.7), one dorsal external mould, NMW2001.38G.423; Locality

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2062, one ventral internal mould, NMW 2001.38G.424 (Fig. 10P); one dorsal external mould, NMW 2001.38G.425 (Fig. 11I), one dorsal internal mould, NMW 2001.38G.426 (Fig. 11G); Locality 2080, one ventral external mould, NMW2001.38G.420 (Fig. 10L), one ventral internal mould, NMW2001.38G.419, three ventral valves, BC 60251–53, three dorsal external moulds, NMW2001.38G.421, 422 (Fig. 10N), 427; Locality 2081 (Hirnantian), two dorsal external moulds, BC 58721 (Fig. 10K), BC 58672 (Fig. 10O). Description. Shell dorsibiconvex, elongate oval, about 120% as long as wide, with maximum width at midlength. Both valves with hemiperipheral growth. Ventral valve weakly convex with submarginal umbo. Cicatrix area small, weakly defined. Dorsal valve lateral profile moderately convex, with maximum height at the umbonal area, steeply inclined from the umbo toward the posterior margin. Dorsal umbo submarginal with a small hemispherical protegulum. Shell surface with up to 14 regular, evenly distributed, thin growth lamellae. Ventral interior with thickened visceral area, bordered by an elevated rim (Fig. 9O, P), about 65% as long and 50% as wide as the valve. Anterior adductor scars large, subtriangular, situated on elevated muscle platforms and bisected by a shallow groove representing an attachment track of oblique internal muscle scars. Dorsal interior with slightly thickened visceral area about 55–60% as long and 50% as wide as the valve. Anterior part of the visceral area occupied by gently impressed, slightly transverse suboval anterior adductor scars bisected by slightly elevated, strongly elongate subtriangular attachment tracks of brachial protractor muscles. Large, composite, posterior adductor and oblique internal muscle scars situated in the posterolateral parts of the dorsal visceral area. Single median scar of the levator ani recognizable in the umbonal area at posterior termination of the visceral area. Narrow, flattened limbus present along the margins of both valves. Remarks. Craniops pristina is the only well-documented Ordovician representative of the genus. Its generic affiliation is based on the presence of the well-developed anterior ventral muscle platforms and slightly elevated dorsal visceral area. A cicatrix attachment area is also present, but it is small and difficult to observe, unlike

J————————————————————————————————————————— Figure 10. A, Ectenoglossa? magna Goriansky, 1972, Katian, Taldyboi Formation, River Ashchisu, Locality 70; NMW 2001.38G.2, ventral valve. B–D, Holmerglossa sp.; Katian, Taldyboi Formation, Locality 1833; B, BC 60211, dorsal internal mould; C, BC 60210, latex cast of dorsal exterior; D, BC 60212, dorsal internal mould. E, F, Trematis aff. taljaardi Rowell, 1970, BC 60213, Hirnantian?, Akdombak Formation, Locality 2080; E, surface microornament; F, ventral view of conjoined valves. G, Monomerella sp., Katian, Akdombak Formation, Locality 7963, NMW 2001.38G.244, ventral exterior. H, Paracraniops ellipticus Goriansky, 1972, Katian, Taldyboi Formation, Locality 1858, NMW 2001.38G.428, dorsal internal mould. I–P, Craniops pristina sp. nov., Hirnantian?, Akdombak Formation; I, J, NMW 2001.38G.425–26, latex cast of dorsal exterior and interior, Locality 2062; K, BC 58721, dorsal external mould, Locality 2081; L, NMW 2001.38G.420, latex cast of ventral exterior, Locality 2080; M, NMW 2001.38G.418, dorsal external mould, holotype, Locality 43; N, NMW 2001.38G.422, ventral external mould, Locality 2080; O, BC 58672, ventral interior, Locality 2081; P, NMW 2001.38G.424, ventral external mould, Locality 2062. Scale bars 2 mm (A–D), 1 mm (E–P).

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Late Ordovician brachiopods Silurian representatives of the genus. It differs from Silurian species (e.g. C. implicata (Sowerby) from Britain and Sweden; C. krizi Mergl, 1986, from the Wenlock of Bohemia, and C. vulcanus Mergl, 1986, from the Ludlow of Bohemia) in having a characteristic sagittal profile of the dorsal valve with a steep, almost orthogonal posterior slope between the umbo and the posterior valve margin.

the uppermost Akdombak Formation (Holorhynchus giganteus Beds) in the area north-east of Mount Akdombak, between the rivers Alpeis and Tolen. However, in that area other craniopside shells occur in Unit T12 (probably Hirnantian), above the Holorhynchus giganteus Beds, but they are not conspecific with Paracraniops ellipticus.

Genus Paracraniops Williams, 1963

Genus Wrightiops gen. nov.

Type species. Craniops? pararia Williams, 1962, from the Kiln Mudstones (Sandbian) of Girvan, Scotland.

Diagnosis. Craniopsid with holoperipheral growth of both valves, like Paracraniops, but lacking a ventral muscle platform and without regular concentric growth lamellae.

Paracraniops ellipticus Goriansky, 1972 (Figs 9F–I, 10H) 1972 Paracraniops ellipticus Goriansky: 173, pl. 45, figs 3–6.

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Holotype. CNIGR 13/9563, ventral external mould (Fig. 9G), Locality 1841, upper part of the Taldyboi Formation (Lower Katian), River Namas, Chingiz Range. Paratypes. Locality 1841 (Katian); one ventral internal mould, CNIGR 16/9563 (Fig. 9F); two dorsal internal moulds, CNIGR 15–16/9563 (Fig. 9F, H). Other material. Katian: Locality 1858; dorsal internal mould, NMW2001.38G.428 (Ld 4.3, W 3.4; Fig. 10H); dorsal external mould, NMW2001.38G.429. Remarks. This species is characterized by a slightly dorsibiconvex, elongate, suboval shell with pointed submarginal umbones in both valves and a posterior margin almost straight in the medial part; surface ornament of fine evenly spaced concentric lamellae. The internal morphology is usually poorly expressed, which makes discrimination between dorsal and ventral valves difficult. Goriansky (1972, p. 172) suggested that the more convex valves are the ventral ones, but comparison with other craniopsides suggests that the opposite is more likely. All the illustrated specimens in the original publication, including the holotype, came from the upper part of the Taldyboi Formation (Early Katian) exposed between the Taldyboi and Namas rivers in the Chingiz Range. Goriansky (1972) also recorded the presence of the species in

Derivation of name. To honour the late Anthony Wright for his outstanding work on brachiopods. Type species. Paracraniops nikitini Goriansky, 1972, see below. Remarks. In the Treatise (Popov & Holmer 2000) there are only four undoubted genera within the family of which only Craniops and Paracraniops are characterized by holoperipheral growth in both valves. However, unlike both those genera, there is no ventral muscle platform and well-developed concentric lamellae in the new genus. Wrightiops is quite abundant in the Taldyboi Formation of the Chingiz-Tarbagatai Terrane, but is unknown elsewhere. Wrightiops nikitini (Goriansky, 1972) (Fig. 11A–F) 1972 Paracraniops nikitini Goriansky: 173, pl. 45, figs 7–10. Holotype. CNIGR 17/9563, lower part of the Taldyboi Formation (Early Katian), River Taldyboi, Chingiz Range. Material. Locality 282 (Early Katian), ventral valve, NMW 2001.38G.439, dorsal valve, NMW 2001.38G.440; Locality 1830, two dorsal internal moulds, BC 58910, NMW 2001.38G.434 (Fig. 11E), ventral valve, NMW 2001.38G.430 (Lv 5.3, W 4.5; Fig. 11A), ventral internal mould, NMW 2001.38G.433 (Fig. 11D), two dorsal

J————————————————————————————————————————— Figure 11. A–F, Wrightiops nikitini (Goriansky, 1972), Katian, Taldyboi Formation, Locality 1830; A, NMW 2001.38G.430, ventral exterior; B, NMW 2001.38G.431, dorsal exterior; C, NMW 2001.38G.432, dorsal exterior; D, NMW 2001.38G.433, ventral internal mould; E, NMW 2001.38G.434, dorsal internal mould; F, NMW 2001.38G.435, dorsal internal mould. G, I, Craniops pristina sp. nov., Akdombak Formation (Hirnantian?); G, dorsal interior, NMW 2001.38G.426; I, dorsal exterior, NMW 2001.38G.425, Locality 2062. H, K–M, R, Testaprica ajaguzensis (Borissiak, 1955); H, BC 58825, dorsal internal mould, Locality 3115; K, BC 58819, latex cast of dorsal exterior, Locality 3115; L, M, BC 58811, internal mould and latex cast of ventral interior, Locality 3115; R, NMW 2001.38G.471, latex cast of dorsal view of incomplete conjoined valves, Locality 3132. J, N–Q, Strophomena (Tetraphalerella) namasensis sp. nov., Locality 1858; J, NMW 2001.38G.472, latex cast of ventral exterior of juvenile specimen; N, BC 60214, holotype, latex cast of dorsal interior; O, BC 60223, latex cast of incomplete ventral exterior showing enlarged radial ornament; P, BC 60215, ventral internal mould; Q, NMW 2001.38G.473, latex cast of incomplete ventral exterior. Scale bars 1 mm (A–G, I, J, Q), 2 mm (H, K, L–P, R).

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valves, NMW 2001.38G.431 (Ld 6.7, W 6.4; Fig. 11B), 432 (Ld 5.7, W 5.0; Fig. 11C), nine undifferentiated dorsal and ventral valves, BC 58910, BC 60276–83; Locality 2423, 30 undifferentiated dorsal and ventral valves, NMW 2001.38G.399–407, 442–446, 460, 526, 535.1–2, 576–581, 787, BC 60272–75. Description. Shell subequally biconvex, nearly smooth apart from occasional holoperipheral growth lines, and weak submarginal umbones in both valves; about 105– 115% as long as wide; transverse profile of both valves gently and slightly unevenly convex, with maximum height slightly posterior to the mid-length. Interior of both valves with slightly raised visceral areas bordered by a low rim and extending anteriorly to the mid-valve. Muscle scars in both valves radially arranged, with distinctive tracks. In the dorsal valve, paired posterior adductor and outside lateral muscle scars form a strongly impressed vshaped composite muscle field (Fig. 10E, F). The tip of this platform is located in the umbonal area and probably represents the attachment scar of levator ani. Mantle canals pinnate in both valves and with paired vascula media and vascula lateralia. The proximal ends of the vascula lateralia in both valves are slightly anterior to the distal parts of the posterior adductor tracks.

Remarks. Broken and disarticulated valves of Monomerella sp. are relatively common in Unit 4 of the Akdombak section, forming lens-like shell accumulations. The illustrated specimen is probably conspecific with those described by Borissiak (1955) from the upper reaches of the River Sary-Bulak in the Chingiz Range. There is some doubt about the generic attribution of these shells, but their preservation is not good enough for more precise taxonomic definition. € Order Strophomenida Opik, 1934 Superfamily Strophomenoidea King, 1846 Family Strophomenidae King, 1846 Subfamily Strophomeninae King, 1846 Genus Strophomena de Blainville, 1824 Type species. Leptaena planumbona Hall, 1847, from the Trenton Group (Katian) of Cincinnati, Ohio, USA. Subgenus Strophomena (Tetraphalerella) Wang, 1949 Type species. Tetraphalerella cooperi Wang, 1949, from the Elgin Limestone Formation (Katian) of Iowa, USA. Strophomena (Tetraphalerella) namasensis sp. nov. (Fig. 11J, N–Q)

Order Trimerellida Goriansky & Popov, 1985 Superfamily Trimerelloidea Davidson & King, 1872 Family Trimerellidae Davidson & King, 1872 Genus Monomerella Billings, 1871

1984 Strophomena phyaliformis Klenina: 90 pars, pl. 10, figs 7, 8 (non figs 4, 5).

Type species. Monomerella prisca Billings, 1871, from the Guelph Formation (Silurian) of Ontario, Canada, and Niagara Limestone of Illinois, USA, by subsequent designation of Davidson & King (1874, p. 155).

Diagnosis. Strophomena (Tetraphalerella) with a relatively wide ventral muscle field occupying almost half valve length and robust, posteriorly directed cardinal process lobes.

Monomerella? antiqua Goriansky, 1972

Derivation of name. After Namas River near the type locality.

1972 Monomerella antiqua Goriansky: 170, pl. 46, fig. 4. 1997 Monomerella? antiqua Goriansky; Popov et al., 591, fig. 4.18.

Holotype. BC 60214 (Fig. 11N), dorsal internal mould, from the Taldyboi Formation (Katian), Locality 1858, Namas River, Chingiz Range.

Holotype. CNIGR 9/9563, ventral internal mould from the Taldyboi Formation (Katian), Locality 1836, River Taldyboi, Chingiz Range.

Paratypes. Locality 1858; one ventral external mould, BC 60223 (Fig. 11O), one ventral internal mould. BC 60215 (Fig. 11P), two ventral external moulds, NMW 2001.38G.472 (Fig. 11J), 473 (Fig. 11Q).

Remarks. This rare species was re-illustrated and discussed in detail by Popov et al. (1997). Monomerella sp. (Fig. 10G) 1955 Monomerella sp.; Borissiak: 30, pl. 1, figs 1–4. Material. Akdombak Formation (Katian). Locality 7963, NMW 2001.38G.244, ventral valve (Lv 19.4, W 20.6).

Description. Shell resupinate, slightly transverse, semioval outline, with maximum width at hinge line. Cardinal extremities slightly acute, with anterior commissure rectimarginate. Ventral valve lateral profile very gently and evenly concave anteriorly, with slightly raised umbo. Ventral interarea moderately high, apsacline, with a broad, convex pseudodeltidium. Dorsal valve lateral profile flattened posteriorly to the mid-valve and moderately convex anteriorly, with maximum height at about one-

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Late Ordovician brachiopods third valve length. Dorsal interarea linear, anacline. Radial ornament slightly unequally parvicostellate, with up to 5 parvicostellae per mm along the anterior margin of mature specimens. Rounded parvicostellae separated by very narrow interspaces, with every second to fourth rib slightly accentuated. Concentric ornament of densely packed, elevated fila, about 20–22 per mm. Ventral interior with large, transverse teeth supported by short widely divergent dental plates continuing as low muscle-bounding ridges, well defined laterally but which gradually fade at the anterior muscle field margin. Muscle field large and subpentagonal, just under half maximum valve length. Adductor scars slightly thickened anteriorly, enclosed by larger diductor scars. Dorsal interior with massive double cardinal process occupying most of the low and narrow notothyrial platform, with the posterior faces of the lobes deeply grooved: a fine ridge, rapidly fading anteriorly, occupies the interspace between the lobes. Socket ridges high, sygmoidal and blade-like, with their outer parts strongly curved towards the hinge. Dorsal adductor muscle scars weakly impressed, bisected by a broad, weakly defined myophragm. Dorsal transmuscle ridges and median septum absent. Remarks. This is the second record of Strophomena (Tetraphalerella) outside Laurentia. Strophomena (Tetraphalerella) bestiubensis (Nikitin et al., 2003) is another Kazakh representative of the subgenus, which was documented from the Tauken Formation (Lower Katian) of the Selety Terrane (Fig. 2). S. (T.) namasensis differs from the former in having a large, transverse ventral muscle field, a robust cardinal process with deeply grooved lobes, and strong, sygmoidal socket ridges strongly curved towards the hinge. Strophomena (T.) namasensis differs from the type species S. (T.) cooperi in the relatively wider, transverse ventral muscle field in contrast to the relatively longer field of S. (T.) cooperi, in the posteriorly directed and rather larger cardinal process lobes, in contrast to the erect lobes of S. (T.) cooperi, and in a broader and weaker dorsal myophragm, which is also longer than the smaller but better-defined myophragm of S. (T.) cooperi. Genus Holtedahlina Foerste, 1924 Type species. Leptaena sulcata de Verneuil, 1848, from the Cincinnatian (Katian) of Ohio, USA. Holtedahlina aff. orientalis Popov & Cocks, 2006 (Fig. 12F–J) Material. Locality 8506 (Mid Katian): two ventral internal moulds, BC 58781 (L>9.2, W 18.1, Sw 5.6, Ml 3.2, Mw 4, Fig. 12J), BC 58782 (Fig. 12H, I), one dorsal internal mould, BC 58743 (Fig. 12F, G). Remarks. These specimens resemble topotypes of Holtedahlina orientalis Popov & Cocks, 2006, from the Lower

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Katian Dulankara Formation of the Chu-Ili Range in south-central Kazakhstan, in having a strongly transverse shell, a strong ventral sulcus developing anterior to midlength and a ventral muscle field almost completely enclosed by muscle bounding ridges. However, the solitary dorsal interior, BC 58743 (Fig. 12F, G), although deformed, has a muscle field that is extended further anteriorly than the Dulankara specimens, which makes firm attribution to the Dulankara species uncertain. Subfamily Furcitellinae Williams, 1965b Genus Bellimurina Cooper, 1956 Type species. Leptaena charlottae Winchell & Schuchert, 1892, from the Katian of Minnesota, USA. Bellimurina (Bellimurina) sp. (Fig. 12A–E) Material. Locality 7975 (Mid Katian): a pair of conjoined valves, NMW 2001.38G.3 (Fig. 12A, B), 6, one ventral valve, NMW 2001.38G.5, one dorsal valve, NMW 2001.38G.4 (Fig. 12C); Locality 3132 (Mid Katian): one dorsal external mould, NMW 2001.38G.474 (Fig. 12D); one dorsal internal mould, NMW 2001.38G.475 (Fig. 12E). Remarks. In having a dorsally geniculated lateral shell profile and fine radial ornament with 6–7 parvicostellae per mm, the specimens from the lower part of the Akdombak Formation resemble Bellimurina (B.) sarytumensis Popov et al., 2002 from the Anderken Formation (Sandbian) of the Chu-Ili Range, southern Kazakhstan. However, the single dorsal interior from Locality 7975 has a more prominent pair of side septa, a finer median septum, and coarser and more regular concentric rugellae than B. (B.) sarytumensis. It may represent a new species, but the material available is inadequate for its formal erection. Genus Katastrophomena Cocks, 1968 Type species. Strophomena antiquata woodlandensis Reed, 1917, from the Woodland Formation (Late Rhuddanian), Girvan, Scotland. Katastrophomena sp. (Fig. 12N) Material. Locality 2080 (Hirnantian?), one ventral internal mould, BC 58855, and one dorsal external mould, BC 58856 (both on Fig. 12N). Locality 2081 (Hirnantian): one ventral internal mould, BC 58677. Remarks. There is not enough material to name a species; however, the sparse material is typical of the genus, which is relatively cosmopolitan, ranging from the Lower Katian into the Silurian.

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Late Ordovician brachiopods Genus Luhaia R~ o~ omusoks, 1956

1984 Luhaia bakanasensis Klenina: 92, pl. 9, figs 8, 10–12.

Remarks. When Percival (2009) erected the genus, he did not have any ventral interiors, but that deficiency can now be made good through the Kazakh material of T. ajaguzensis redescribed and illustrated here. As stated by Percival (2009, p. 166), the only rafinesquinine with a similar convexoconcave valve profile to Testaprica is Rhipidomena, which is also of comparable size; however, the latter has ovoidal (rather than pentagonal) and much weaker ventral muscle-bounding ridges, and the ventral diaphragm is far less prominent.

Holotype. IGNA 411/179, conjoined valves, from Klenina’s Locality 511, the Katian part of the Akdombak Formation, east side of Tolen River.

Testaprica ajaguzensis (Borissiak, 1955) (Figs 11H, K–M, R, 12W)

~musoks, 1956, from the Type species. Luhaia vardi R~ oo Pirgu Formation (Katian) of Estonia. Luhaia? bakanasensis Klenina, 1984 (Fig. 12K–M)

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Material. Locality N-511. In addition to Klenina’s material, Locality 1756, seven conjoined valves, BC 58786 (Fig. 12K–M), BC 58787–90, BC 58792–93, one dorsal valve, BC 68791; Locality 669, conjoined valves, BC 58826. Remarks. The few specimens available are partly silicified and preserved in siliciclastic rock, which makes it impossible to see the cardinalia. There are no data on the cardinalia in Klenina’s original description and no valve interiors were illustrated. Luhaia? bakanasensis probably represents a valid taxon, but its generic affiliation is highly doubtful and it cannot be resolved from the material available for study, although it is similar to Luhaia in its shape and large size. The paratypes in the Institute of Geological Sciences, Almaty, are also not helpful in resolving the identity of this large and externally very distinctive species. Family Rafinesquinidae Schuchert, 1893 Subfamily Rafinesquininae Schuchert, 1893 Genus Testaprica Percival, 2009 Type species. Testaprica rhodesi Percival, 2009, from the Gunningbland Formation (Katian) of New South Wales, Australia.

1955 Strophomena ajaguzensis Borissiak: 53, pl. 6, figs 1–6. Lectotype. CNIHR 64/7304, designated here, a dorsal internal mould, the original of Borissiak (1955, pl. 6, Fig. 3a, b), from the Akdombak Formation (Katian), area north of the Mount Kara-Buzhir, Chingiz Range. Material. Locality 3115 (Mid Katian), ventral internal and external moulds, BC 58811 (Fig. 11L, M) (L >9.2, W 18.1, Sw 5.6, Ml 3.2, Mw 4.7), BC 58812, two ventral internal moulds, BC 59132–33, one dorsal external mould, BC 58819 (Fig. 11K), six dorsal internal moulds, BC 58825 (Fig. 11H) (L 16.8, W approx. 23), NMW 2001.38G. 225–227, 229, 482 (Fig. 12W); Locality 3132 (Mid Katian), one incomplete external mould of conjoined valves, NMW 2001.38G.471 (Fig. 11R). Description. Shell strongly concavoconvex, transverse and suboval in outline, with maximum width at or immediately anterior to the hinge line. Cardinal extremities slightly acute to almost rectangular. Anterior commissure rectimarginate, broadly rounded. Ventral valve gently and evenly concave, with an apsacline interarea and a triangular delthyrium completely covered by a convex pseudodeltidium. Lateral profile of dorsal valve strongly convex,

J————————————————————————————————————————— Figure 12. A–E, Bellimurina (Bellimurina) sp.; A, B, NMW 2001.38G.3, ventral and dorsal views of conjoined valves; C, NMW 2001.38G.4, dorsal interior, Locality 7975; D, NMW 2001.38G.474, dorsal external mould, Locality 3132; E, NMW 2001.38G.475, dorsal internal mould, Locality 3132; F–J, Holtedahlina aff. orientalis Popov & Cocks; Locality 8506; F, G, BC 58743, latex cast of dorsal interior and dorsal internal mould; H, I, BC 58782, ventral internal mould and latex cast of ventral interior; J, BC 58781, ventral internal mould. K–M, Luhaia? bakanasensis Klenina, 1984, Locality 1756, BC 58786, conjoined valves in posterior, ventral and dorsal views. N, Katastrophomena sp., Locality 2080, BC 58855, ventral internal mould and BC 58856, dorsal external mould of orthotetoidean. O–T, Leptaena (Leptaena) enucleata Klenina, 1984; O, BC 58718, dorsal internal mould, Locality 2080; P, BC 58675, dorsal external mould, Locality 2081; Q, BC 58717, dorsal internal mould, Locality 2080; R, BC 58838, ventral exterior, Locality 2080; S, BC 58719, dorsal internal mould, Locality 2080; T, BC 58676, latex cast of dorsal exterior, Locality 2081. U, V, Buminomena abayi (Klenina, 1984), Locality 1838, NMW 2001.38G.481, internal mould and latex cast of ventral interior. W, Testaprica ajaguzensis (Borissiak, 1955), Locality 3115, NMW 2001.38G.482, dorsal internal mould. X, Y, Christiania aff. proclivis Popov & Cocks, 2006; X, NMW 2001.38G.468, dorsal internal mould, Locality 667; Y, BC 58742, dorsal external mould, Locality 3136. Z, A0 , Shlyginia sp. 2, Locality 3136; Z, NMW 2001.38G.466, ventral internal mould; A0 , BC 58741, ventral internal mould. B0 , Cliftonia sp., Locality 2080, BC 60216, latex cast of dorsal external mould. Scale bars 2 mm (A–J, N–B0 ), 5 mm (K–M).

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with maximum height slightly posterior to mid-length and flattened posterior slope. Dorsal interarea low, planar, apsacline; chilidial plates obscure. Radial ornament finely and almost evenly multicostellate with 4–6 ribs per 2 mm along the posterior margin of mature specimens, with irregular oblique rugellae along the dorsal posterior margin. Ventral interior with small teeth supported by low and divergent dental plates continuing as evenly rounded muscle-bounding ridges almost completely enclosing the ventral muscle field, with a narrow gap in the middle. Adductor scars lenticular, bisected throughout their entire length by a narrow median ridge which completely separates the diductor scars. Mantle canal impressions very poorly impressed, apart from the slightly divergent proximal parts of the vascula media. Prominent subperipheral rim near the lateral and anterior valve margins. Dorsal interior with delicate bilobed cardinal process, and straight, widely divergent socket plates. A pair of prominent side septa extends to the mid-valve, but median and outer side septa are absent. Remarks. This species resembles the type and only other known species Testaprica rhodesi in having a concavoconvex shell with almost equally multicostellate ornament, rafinesquinid-type cardinalia and a pair of prominent dorsal side septa extending almost to the midvalve. Testaprica ajaguzensis can be distinguished from the Australian shells in having a strongly apsacline ventral interarea, and in the presence of distinct oblique rugellae along the dorsal valve posterior margin. Subfamily Leptaeninae Hall & Clarke, 1894 Genus Leptaena (Leptaena) Dalman, 1828 Type species. Leptaena rugosa Dalman, 1828, from the Dalmanitina Beds (Hirnantian) of V€asterg€ otland, Sweden. Leptaena (Leptaena) enucleata Klenina, 1984 (Fig. 12O–T) 1984 Leptaena (Leptaena) enucleata Klenina: 101, pl. 8, figs 12–16. Holotype. IGNA 411/158, an exfoliated ventral valve from Locality 593 of Klenina (1984), the Hirnantian part of the Akdombak Formation, from the left hand side of Bakanas River, north-west of Akdombak Mountain. Material. In addition to Klenina’s material, Locality 2080 (Hirnantian?) has yielded the exterior of conjoined valves, BC 60270, two ventral valves, BC 58838 (Fig. 12R), BC 58717 (Fig. 12Q), six dorsal valves, BC 58678, BC 58718 (Fig. 12O), BC 58719 (Fig. 12S), BC 58840–1, BC 60271; and Locality 2081, ventral valves, BC 58673, BC 58675 (Fig. 12P), BC 60243, dorsal valves, BC 58674, BC 58676 (Fig. 12T).

Description. Shell concavoconvex, with sharp anterior dorsal geniculation. Outline transverse subtrapezoidal, with maximum width at hinge line; cardinal extremities acute and alate. Ventral valve lateral profile very gently convex posterior to the geniculation, accentuated by high, angular rim and corresponding to the valve highest point. Ventral interarea apsacline with a small, convex pseudodeltidium. Dorsal valve concave, almost flat posterior to the geniculation. Dorsal interarea low, anacline, with strong, convex chilidium. Radial ornament almost equally multicostellate, with 4 to 5 rounded ribs per mm along the anterior margin of mature specimens. Concentric ornament with 5 to 8 slightly undulating rugae posterior to the geniculation and fine, crowded filae from 10 to 12 per mm. Ventral interior with small teeth, supported by thin, widely divergent dental plates. Ventral muscle field almost circular, surrounded by strong muscle bounding ridges. Dorsal interior with a double cardinal process on a low notothyrial platform, and low, almost straight, broadly divergent socket plates. Median septum and a pair of transmuscle ridges variably developed, which may be strong in some specimens and almost indiscernible in others from the same population. Remarks. Leptaena ranges in age from the Darriwilian to the Early Devonian, but Klenina’s species is of the same age as the Swedish type species, which was revised by Bergstr€om (1968), and is indeed very close to it, particularly in its interiors, although, as usual with Leptaena, there is wide variation in the morphology. However, Leptaena (L.) enucleata differs in being relatively wider and in having consistently stronger rugae than L. (L.) rugosa. The latter species is a widespread constituent of the cosmopolitan Hirnantia Fauna. Nikitin (in Apollonov et al. 1980, pp. 56–57, pl. 16, figs 14–17, pl. 17, figs 4–12) identified and described L. rugosa and L. aff. rugosa from the latest Katian and Hirnantian of the Chu-Ili Terrane, but both suites of specimens are more similar to L. (L.) rugosa than to L. (L.) enucleata. Family Glyptomenidae Williams, 1965b Subfamily Glyptomeninae Williams, 1965a Remarks. When Cocks (2005) erected Ungulomena from the Late Katian Boda Limestone of Sweden, it was the only genus within a new subfamily Ungulomeninae, which is distinguished from the other two subfamilies in the Glyptomenidae, Glyptomeninae and Teratelasminae, in the geniculation of the dorsal valve and in the presence of a dorsal diaphragm. Buminomena abayi has a structure very similar to a diaphragm, but it is only present in one specimen, and probably represents a teratological distortion of the shell, and the new genus is thus attributed to Glyptomeninae. However, Glyptomenoides Popov & Cocks, 2006, whose type species is Rafinesquina

Late Ordovician brachiopods girvanensis Salmon, 1942, from the Balclatchie Formation (Sandbian) of Girvan, Scotland, and which is known from the Sandbian and Katian of Laurentia and the ChuIli Terrane (Popov & Cocks 2006), possesses both dorsal geniculation and a diaphragm, and is thus transferred here to the Ungulomeninae. Genus Buminomena gen. nov.

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Diagnosis. Glyptomeninid with gently convex ventral valve, becoming more convex anteriorly, and geniculate dorsal valve. Type C cardinal process of Rong & Cocks (1994). Bilobed ventral muscle field with strong musclebounding ridges except anteriorly. Short dorsal valve median septum confined to valve centre, vestigial to absent in some specimens. Dorsal diaphragm and side septa absent; weak subperipheral rim occasionally developed. Derivation of name. After Bumin Qaghan, the legendary founder of the Turkic Khaganate in Central Asia. Type and only species. Oepikina abayi Klenina, 1984, from the Taldyboi Formation (Katian), of the Chingiz Range, Kazakhstan. Remarks. Buminomena is placed within the Glyptomeninae because of its lack of both median and side septa in the dorsal interior. Within the subfamily, it is closest to Glyptomena itself; however, the ventral valve is more convex, the muscle bounding ridges are very much stronger and the socket plates are straighter and directed more anterolaterally than in Glyptomena. The ornament of Buminomena differs in becoming almost multicostellate near the valve margins, in contrast to Glyptomena which is uniformly parvicostellate over the whole shell. The pseudodeltidium in Buminomena is large, completely covering the delthyrium, in contrast to the very small pseudodeltidium in Glyptomena. Amongst other glyptomenines Resupinsculpta Percival, 2009 has a similar dorsal valve interior, but is resupinate. Buminomena abayi (Klenina, 1984) (Figs 12U, V, 13G, J–U) 1984 Oepikina abayi Klenina: 95, pl. 9, fig. 1. Holotype. IGN 422/170, ventral valve, from the Taldyboi Formation (Katian), Locality 3519, Boskombai River, Chingiz Range, Kazakhstan. Material. Locality 70 (Early Katian), three ventral internal moulds, NMW 2001.38G.463 (Lv 16.6, W 19.5, T 6.1, Ml 7.8, Mw 7.5; Fig. 13S), 464 (Lv 13.6, T 4.8, Ml 6.7; Fig. 13M), NMW 2001.38G.480; BC 59913 (Ld 12.0, W 15.7: Fig. 13N, U); Locality 1838 (Early Katian), two ventral internal moulds, NMW 2001.38G.461 (Lv

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1.3, W 14.8, T 6.0, Ml 4.3, Mw 4.3, Fig. 13T), 481 (Fig. 12U-V); Locality 1858 (Early Katian), one external mould of dorsal valve and conjoined ventral interarea, BC 58909 (L approx 13, W approx 30); Locality 2133 (Early Katian), one ventral internal mould, BC 59911 (Lv 16.4, W 21.4, Fig. 13K), two dorsal internal moulds, BC 59912 (Ld 1.05, W 15.4, Fig. 13R); Locality 2423 (Early Katian), exterior of conjoined valves, BC 60284, ventral valve, BC 60221 (Fig. 13G, J), ventral internal mould, BC 60220 (Fig. 13Q). Description. Shell strongly concavoconvex, about fourfifths as long as wide, with the maximum width at the hinge line. Cardinal extremities acute to almost right angled. Anterior commissure rectimarginate. Ventral valve lateral profile almost evenly convex, slightly more strongly anterior to mid-length. Ventral interarea planar, apsacline with a delthyrium completely covered by the convex pseudodeltidium. Dorsal valve almost flat with a weak dorsal geniculation along the anterior and lateral margins of the mature specimens. Dorsal interarea low, planar, almost procline with a complete chilidium. Radial ornament unequally and finely parvicostellate, with up to five parvicostellae in the interspaces between accentuated ribs in the mid-valve; becoming more nearly multicostellate near the anterior margin of mature specimens, with 5–7 ribs per mm. Concentric ornament of very fine densely spaced fila. Ventral valve interior with fine teeth and thin, strongly divergent dental plates. Ventral muscle field subpentagonal and bilobed, about two-fifths as long as the valve, surrounded by strong muscle bounding ridges anteriorly and laterally. Adductor scars narrow, thickened almost half length of diductor scars, but not completely enclosed. Ventral vascula media fine, divergent. Dorsal interior with bilobed ‘Type C’ cardinal process of Rong & Cocks (1994) situated on a vestigial notothyrial platform. Long and almost straight, widely divergent, socket ridges bordering transverse sockets with five ridges on the anterior slope. Adductor scars slightly thickened, not divided by side septa. Faint median septum variably developed in valve centre. Very weak, short and curved dorsal side septa only in the valve centre. Diaphragm variably developed in both valves. Remarks. Only the ventral valve exterior was shown in the original publication, where description of the interiors in both valves was not supported by illustrations. However, there is no doubt that specimens in our studied collection are conspecific with the types of Oepikina abayi Klenina, 1984, since they were sampled within the type area and unit, and since there are no other large strophomenoids known from there with strongly concavoconvex shells. The species shows considerable variation in the dorsal valve morphology; in particular, differences between the two well-preserved dorsal interiors from Ashchisu are striking. In one specimen there is both a median

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712 L. E. Popov and L. R. M. Cocks

Late Ordovician brachiopods septum and a diaphragm which, although weak and not raised as in Ungulomena, are clearly developed (Fig. 13N), whilst in the other specimen (Fig. 13N, O, R) there is the merest trace of them. Genus Platymena Cooper, 1956 Type species. Platymena plana Cooper, 1956, from the Arline Formation (Sandbian) of Tennessee, USA.

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Platymena? sp. (Fig. 13B) Remarks. A single ventral internal mould, BC 58824, from Locality 3115 of the Akdombak Formation, is similar to specimens of Platymena from many parts of the world; however, without dorsal interiors, the identification can only be questionable. Platymena tersa was described from the Degeres Member of the Dulankara Formation of the adjacent Chu-Ili Terrane of Kazakhstan by Popov & Cocks (2006) and the Akdombak specimen might fall within its range of variation; however, the latter has less well-developed muscle bounding ridges than most ventral valves of P. tersa. Family Foliomenidae Williams, 1965 Genus Foliomena Havlıcek, 1952 Type species. Strophomena folium Barrande, 1879, from  the Kraluv Dvur Formation (Late Katian-Hirnantian) of Bohemia, Czech Republic. Foliomena folium (Barrande, 1879) (Fig. 13C–F, H–I) 1879 Strophomena folium Barrande: pl. 55. 1967 Foliomena folium (Barrande); Havlıcek: 83, pl. 9, figs 1–3, 6–7, 10, 13. 1973 Foliomena folium (Barrande); Sheehan: 64, pl. 2, figs 13–18, pl. 3, figs 1–3. Material. Locality 2083 (Late Katian): one ventral internal mould, BC 58735 (L 4.5, W 7.4 approx), one dorsal internal and external mould, BC 58860 (L approx 9, W 14.0, Fig. 13D, E); four dorsal external moulds, BC

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58737 (L 5.1, W 12.0), BC 58861, BC 58737; BC 60219 (Fig. 13H, I). Remarks. Although the material is sparse, the well-preserved dorsal external and internal mould from the Akdombak Formation is essentially identical to the specimen from Bohemia illustrated by Havlıcek (1967, pl. 9, fig. 13), and the more obscure Kazakh ventral interior also appears to be conspecific with Bohemian ventral interiors on the same plate. The species is characteristic of the cosmopolitan deeper-water Foliomena Fauna reviewed by Rong et al. (1999). Family Christianiidae Williams, 1953 Genus Christiania Hall & Clarke, 1892 Type species. Leptaena subquadrata Hall, 1883, from the Lenoir Formation (Darriwilian) of Tennessee, USA. Christiania aff. proclivis Popov & Cocks, 2006 (Fig. 12X, Y) Material. Akdombak Formation (Katian). Locality 8506 (Mid Katian), one ventral internal mould, BC 58785, one mould of conjoined valves, BC 58783 (L 32.0, W 23.8), dorsal internal mould, BC 58784; Locality 3136 (Mid Katian), one dorsal external mould, BC58742 (Fig. 12Y); Locality 667 (Mid Katian), one dorsal internal mould, NMW 2001.38G.468 (Ld 21.9, W 12.3, Iw 10.6; Fig. 12X). Remarks. These specimens, with the length of the dorsal valve exceeding 30 cm, are amongst the largest yet known representatives of the genus. In having an elongate, subrectangular shell (L/W 135% for a dorsal valve), a shallow ventral median sulcus and a low dorsal median fold fading anteriorly, a short dorsal median septum not extending to the mid-valve and in the absence of radial ornament, it most resembles Christiania proclivis Popov & Cocks, 2006, from the Lower Katian Dulankara Formation of the Chu-Ili Range in south-central Kazakhstan, but the limited material available and the considerable distortion of the studied shells makes further comparison difficult; they may well represent a closely related but separate taxon.

J————————————————————————————————————————— Figure 13. A, Eostropheodonta aff. hirnantensis (M’Coy, 1851), Locality 2080, BC 60218, ventral view of internal mould of conjoined valves. B, Platymena? sp., Locality 3115, BC 58824, ventral internal mould. C–F, H–I, Foliomena folium (Barrande, 1879), Locality 2083; C-F, BC 58860, dorsal internal mould, latex cast of dorsal internal mould and enlarged view of cardinalia; H, I, BC 60219, ventral internal mould and latex cast of ventral interior. G, J–U, Buminomena abayi (Klenina, 1984); G, J, BC 60221, lateral and ventral views of ventral exterior, Locality 2423; K, L, BC 59911, ventral internal mould posterior and ventral views, Locality 2133; M, NMW 2001.38G.464, ventral internal mould, Locality 70; N, U, BC 59913, dorsal internal mould and latex cast of interior, Locality 2133; P, S, side and ventral views of ventral internal mould, Locality 70; O, R, BC 59912, dorsal internal mould and latex cast of dorsal interior, Locality 2133; Q, BC 60220, latex cast of dorsal view of conjoined valves, Locality 2423; S, NMW 2001.38G.463, ventral internal mould, Locality 70; T, NMW 2001.38G.461, ventral internal mould, Locality 1838. V, Kassinella kasbalensis sp. nov., NMW 2001.38G.782, ventral internal mould, Locality 3126. W, Diambonioidea koknaiensis sp. nov., Locality NMW 2001.38G.795, dorsal view of conjoined valves, Locality 2088. X, Olgambonites? sp., Locality 3114, BC 58703, ventral internal mould. Scale bars 2 mm.

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Popov & Cocks (2006, p. 263) gave a detailed discussion of the Late Ordovician species assigned to the genus. Family Leptostrophiidae Caster, 1939 Genus Eostropheodonta Bancroft, 1949 Type species. Orthis hirnantensis M’Coy, 1851, from the Hirnant Formation (Hirnantian), near Bala, Wales.

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Eostropheodonta aff. hirnantensis (M’Coy, 1851) (Figs 13A, 19E–H) Material. Locality 2080 (Hirnantian?): three ventral external moulds, BC 58835, BC 58853–54, two ventral internal moulds, BC 60218 (Fig. 13A) and BC 58893 (Fig. 19H), four dorsal valves, BC 58691, BC 58692 (Fig. 19E, F, L 27.3, est. W 39), BC 58693 (Fig. 19G, est. L 27, est. W 48), BC 58855, two external moulds, BC 58834, BC 58691; Locality 2081, two pairs of conjoined valves, BC 60218 (Fig. 13A, L>22, W 50.1), BC 58778a (L 8.0, W 15.4), two ventral valves, BC 58686–7, ventral external mould, BC 58678. Remarks. Although no good dorsal interior is yet known from the Hirnantian of the Akdombak Formation, the distinctive curved and slightly wavy parvicostellate ornament and the shell shape are uniquely characteristic of Eostropheodonta, which is a common and relatively cosmopolitan constituent of the Hirnantia Fauna, and it would not be surprising if the Kazakh form eventually turns out to be E. hirnantensis itself. These shells differ from Eostropheodonta bublitscheki Nikitin in Nikitin et al., 1980, from the Zhalair Formation (Hirnantian) of the Chu-Ili Range (southern Kazakhstan), in having a more transverse outline, acute cardinal extremities and differentiated, parvicostellate (not multicostellate) radial ornament. Superfamily Plectambonitoidea Jones, 1928 Family Leptellinidae Ulrich & Cooper, 1936 Genus Acculina Misius in Misius & Ushatinskaya, 1977 Type species. Acculina acculica Misius in Misius & Ushatinskaya, 1977, from the Tabylgaty Formation (Sandbian: Nemagraptus gracilis Biozone), Moldo-Too Range, North Kyrgyzstan. Acculina phyaliformis (Klenina, 1984) (Fig. 14A0 , B0 , H0 ) 1984 Strophomena phyaliformis Klenina: 90 pars, pl. 10, figs 4, 5 (non figs 7, 8).

Holotype. IGNA 411/185, conjoined valves from Locality 604 of Nikitin (1972), in the upper part of the Taldyboi Formation, Taldyboi River, Chingiz Range. Material. Locality 1835 (Early Katian): ventral internal mould (topotype), BC 58879 (Fig. 14 A0 ); Locality 2401 (Mid Katian): dorsal internal mould, BC 58900 (L 17.5, W 34.1) (Fig. 14A0 , B0 ). Description. Shell resupinate, strongly ventrally geniculate, transverse, subtrapezoidal in outline, with maximum width at the hinge line. Cardinal extremities acute and may be slightly alate. Anterior commissure broadly uniplicate. Ventral valve gently convex to mid-length, but strongly ventrally geniculated anteriorly at about two thirds valve length. Ventral interarea low, planar, apsacline, with convex pseudodeltidium. Dorsal valve lateral profile gently concave, becoming strongly convex anteriorly, with maximum height at geniculation at about quarter valve length from the anterior margin. Dorsal interarea linear, planar, anacline with a pair of chilidial plates almost completely uniting centrally. Ventral interior with short stubby teeth united with dental plates diverging at about 50 and extending anteriorly for about one-third valve length, Muscle field poorly impressed and open anteriorly. Dorsal interior with small erect cardinal process united anteriorly with weak myophragm extending anteriorly for about half valve length. Short curved socket plates united anteriorly, with the weakly raised margins of the subcircular muscle field. Prominent diaphragm not united with the hinge line, curving laterally for a short distance posteriorly but parallel-sided laterally before curving posterocentrally to form a triple junction in the valve centre with the weak myophragm. Lemniscate mantle canals weakly impressed laterally and anteriorly to the diaphragm. Remarks. Strophomena phyaliformis, as originally defined by Klenina (1984), is a heterogenous taxon. The holotype and another illustrated specimen from Locality 604 (Klenina 1984, pl. 10, figs 4, 5) are resupinate, with strong ventral geniculation, whereas the ventral and dorsal internal moulds with strophomenid features illustrated by Klenina (1984, pl. 10, figs 7, 8) came from the same horizon but from a different site, Locality 604a. The latter lack geniculation, cannot be convincingly considered as congeneric with the holotype, and seem more likely to be Strophomena (Tetraphalerella) sp. as described above. One of two specimens assigned to Acculina here is from the Taldyboi Formation and from the same horizon as Locality 604, and thus we consider it as a topotype, although the species appears rare there. Therefore, assignment of the holotype of ‘Strophomena’ phyaliformis to Acculina can be supported by our new data on the internal morphology of both the ventral and dorsal valves. Very similar specimens from the Anderken Formation of the

Late Ordovician brachiopods Chu-Ili Terrane with strong ventral geniculation were illustrated by Popov et al. (2002, pl. 4, figs 7, 8) as Acculina sp., but may now be assigned to A. phyaliformis. Genus Dulankarella Rukavishnikova, 1956 Type species. Dulankarella magna Rukavishnikova, 1956, Dulankara Formation (Early Katian), Chu-Ili Range, Kazakhstan. Dulankarella? sp. (Fig. 14C0 , D0 )

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Material. Locality 593 (Mid Katian), ventral valve, NMW 2001.38G.467 (Lv 14.3, W>18.5, T 6.5); Locality 3132 (Mid Katian), dorsal external mould, NMW 2001.38G. 736; Locality 8506 (Mid Katian), ventral external mould, BC 58766 (L 15.4, W 16.6). Remarks. Three specimens are questionably attributed to Dulankarella because of their similarity in ventral valve shape and unequally parvicostellate ornament with widely spaced ribs of two to three generations and fine regular parvicostellae between them (Fig. 13D0 ), which, amongst the Late Ordovician plectambonitoideans of Kazakhstan, appears closest to Dulankarella, as described by Popov et al. (2002) and Popov & Cocks (2006) from the Chu-Ili Terrane. However, no interiors are available to confirm this generic identification. Genus Mabella Klenina, 1984 Type species. Leptellina (Mabella) semiovalis Klenina 1984, Taldyboi Formation (Lower Katian), Chingiz Range. Remarks. Revised description of the type species given below supports earlier observations suggesting that Wiradjuriella Percival, 1991, is a junior subjective synonym of Mabella, as was suggested by Cocks & Rong (2000) and Popov et al. (2002). More detailed discussion on the affinities of the species referred to the genus can be found in Percival (1991) and Popov et al. (2002). Mabella semiovalis Klenina, 1984 (Fig. 14F–H, J–T) 1984 Leptellina (Mabella) semiovalis Klenina: 69, pl. 5, figs 1, 3, 4, pl. 9, figs 4, 7. 1984 Leptellina (Mabella) obtusa Klenina: 71, pl. 5, figs 5, 6, pl. 6, fig. 2. 1984 Leptellina (Mabella) incurvata Klenina: 72, pl. 5, fig. 2. Holotype. IGNA 411/79, conjoined valves, Locality 604 of Klenina (1984), upper part of the Taldyboi Formation

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(Katian), Taldyboi River ( ¼ Locality 800 of Klenina 1984). Material. Locality 1836 (Early Katian), seven conjoined valves, eight ventral valves, including BC 60222 (Fig. 14J, K), NMW 2001.38G.494–498, two ventral valves, NMW 2001.38G.499–500; Locality 1858 (Early Katian), three ventral valves, BC 58902–4, one ventral internal mould, NMW 2001.38G.462, three dorsal valves, BC 58905–8; Locality 1841 (Early Katian), two ventral valves, NMW 2001.38G.136 (Fig. 14N), 143 (Fig. 14F, G), three ventral internal moulds, NMW 2001.38G.133 (Fig. 14R), 139 (Fig. 14H, M), 179, five ventral external moulds, NMW 2001.38G.135, 151.11–14; one dorsal external mould with attached ventral interarea, NMW 2001.38G.151.1 (Fig. 14S), seven dorsal external moulds, NMW 2001.38G. 151.3 (Fig. 14O), 151.4–6, 190.1–3, six dorsal internal moulds, NMW 2001.38G.151.1 (Fig. 14S), 151.2 (Fig. 14L, P), 7–10; Locality 1844 (Early Katian), four ventral external moulds, NMW 2001.38G.193.1 (Fig. 14Q), 193.2–4, three ventral internal moulds, NMW 2001.38G.179, 193.5–6, one dorsal external mould, NMW 2001.38G. 193.7, two dorsal internal moulds, NMW 2001.38G. 193.1 (Fig. 14Q), 193.3; Locality 1858 (Early Katian), one ventral internal mould, NMW 2001.38G.279. Description. Shell concavoconvex to almost planoconvex, transverse semioval in outline, with maximum width at hinge line. Cardinal extremities acute and slightly alate; anterior commissure rectimarginate. Ventral valve strongly convex in transverse and lateral profiles with maximum thickness slightly posterior to mid-length. Ventral interarea planar, strongly apsacline to almost orthocline, with a small, convex pseudodeltidium. Dorsal valve gently concave to almost flat, with a planar, anacline to procline interarea and disjunct chilidial plates. Radial ornament finely and unequally parvicostellate, with 5 to 6 accentuated ribs per 3 mm along the anterior margin of mature specimens and up to 7 very fine parvicostellae in the interspaces. Ventral interior with strong teeth lacking dental plates. Ventral muscle field cordate with small adductor scars strongly impressed in the umbonal area, and completely surrounded by diductor muscle scars, bisected by a median ridge in front of the diductor scars. Mantle canals saccate with divergent vascula media bifurcating at a short distance from the ventral muscle field. Dorsal interior with a low, trifid cardinal process facing posteriorly, and straight, widely divergent socket ridges. Lophophore platform occupying almost 90% of valve length, bordered by a high, medially divided rim. Median septum tubular anteriorly, not merging with a rim in juvenile specimens, becoming bifurcated and adjoined with the rim in mature specimens.

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716 L. E. Popov and L. R. M. Cocks

Late Ordovician brachiopods Remarks. This species shows significant variations in proportions, outline and lateral profile of the shell. Therefore, the other species described by Klenina (1984), Leptellina (Mabella) obtusa and L. (M.) incurvata, are considered here as synonymous with the type species of Mabella, particularly since their type material came from the same locality and horizon as M. semiovalis. Juvenile specimens of M. semiovalis resemble M. conferta Popov (1985), from the Anderken Formation (Sandbian) of the Chu-Ili Terrane, in having a tubular dorsal median septum not fused with a rim; however, in mature specimens of M. semiovalis the dorsal median septum becomes bifurcated anteriorly, with anterior terminations touching the margin of the rim bounding a lophophore platform, unlike M. conferta.

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Mabella sp. (Fig. 14A–E, I, G0 ) Material. Locality 7975 (Mid Katian), two pairs of conjoined valves, NMW 2001.38G.31, 15 ventral valves, NMW 2001.38G.17–28, 29 (Fig. 14G0 ), 30, 36, and five ventral internal moulds, NMW 2001.38G.32 (L 6.9, W 7.9), 33–35; Locality 8506 (Mid Katian), three ventral internal moulds, BC 58774, BC 58775 (Fig. 14A), BC 58777; Locality 3088 (Late Katian), external mould of conjoined valves BC 60229 (Fig. 14B), ventral internal mould, BC 58901 (Fig. 14C). Remarks. These specimens are characterized by a strongly and evenly convex ventral valve with a transversely, semioval outline, maximum width at the hinge line, a rectimarginate anterior commissure, and very finely parvicostellate radial ornament. The ventral and dorsal interiors are unknown. External shell shape and radial ornament closely resemble the type species Mabella semiovalis (Klenina, 1984, p. 69) from the Taldyboi Formation (Katian), but there is insufficient detail to make further definitive comparisons. Genus Shlyginia Nikitin & Popov, 1983

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Type species. Shlyginia declivis Nikitin & Popov, 1983, from the Andriushino Formation (Late Darriwilian to Early Sandbian: Tselenograd Regional Stage), north-central Kazakhstan. Shlyginia sp. 1 (Fig. 14U, E0 , F0 ) Material. Locality 7975 (Mid Katian), four conjoined valves, NMW 2001.38G.12 (Fig. 14 E0 , F0 ), 13–16; one ventral internal mould, NMW 2001.38G.11 (Fig. 14U). Remarks. A few specimens from the lower part of Akdombak Formation have a concavoconvex shell, very finely and unequally parvicostellate radial ornament, and a characteristic flabellate ventral muscle field with small, deeply impressed adductor scars completely enclosed by larger diductor scars. The specimens are comparable to Shlyginia fragilis Nikitin & Popov, 1985, which is widespread in the Sandbian of Kazakhstan (Popov et al. 2002). However, they differ in having a more strongly convex lateral profile in the ventral valve and narrower, widely divergent ventral adductor scars. In the absence of dorsal interiors, further comparison and precise definition of these specimens is not possible. Shlyginia sp. 2 (Fig. 12Z, A0 ) Material. Akdombak Formation (Mid Katian). Locality 3136, two ventral internal moulds, NMW 2001.38G.466 (Fig. 12Z), BC 58741 (Fig. 12A0 ); Locality 8506, ventral internal mould, BC 58780. Remarks. The ventral valve, with its geniculated profile and large bilobate ventral muscle field, suggests similarity to Shlyginia extraordinaria (Rukavishnikova, 1956) from the Dulankara Formation (Early Katian) of the Chu-Ili Range, as revised by Popov et al. (2000); however, since the specimens are represented only by ventral internal moulds, species discrimination is impossible.

J————————————————————————————————————————— Figure 14. A–E, I, G0 , Mabella sp.; A, BC 58775, Locality, 8506; B, BC 60229, dorsal view of conjoined valves, latex cast, Locality 3088; C, BC 58901, ventral internal mould, Locality 3088; D, NMW 2001.38G.36, dorsal view of conjoined valves, Locality 7975; E, I, NMW 2001.38G.37, ventral and lateral views of ventral exterior, Locality 7975; G0 , NMW 2001.38G.29, ventral internal mould, Locality 7975. F–H, J–T, Mabella semiovalis (Klenina, 1984); F, G, NMW 2001.38G.143, ventral valve lateral and ventral views, Locality 1841; H, M, NMW 2001.38G.139, ventral valve posterior and ventral views, Locality 1841; J, K, BC 60222, ventral and dorsal views of conjoined valves, Locality 1836; L, P, NMW 2001.38G.151.2, dorsal internal mould and latex cast of dorsal interior, Locality 1841; N, NMW 2001.38G.136, ventral exterior, Locality 1841; O, NMW 2001.38G.151.3, latex cast of dorsal interior, Locality 1841; Q, NMW 2001.38G.193.1, latex cast of ventral exterior, Locality 1844; R, NMW 2001.38G.133, ventral internal mould, Locality 1841; S, NMW 2001.38G.151.1, dorsal view of conjoined valves exterior, latex cast, Locality 1841; T, NMW 2001.38G.193.2, latex cast of dorsal internal mould. U, E0 , F0 , Shlyginia sp. 1, Locality 7975; U, NMW 2001.38G.11, ventral internal mould; E0 , F0 , NMW 2001.38G.12, ventral and dorsal views of conjoined valves. V–Z, Diambonioidea koknaiensis sp. nov., Locality 2083; V, BC 58716, dorsal internal mould; W, BC 58738, ventral internal mould; X, Y, BC 58859, holotype, dorsal internal mould and latex cast of interior; Z, BC 58863, dorsal exterior. A0 , B0 , H0 , Acculina phyaliformis (Klenina, 1984); A0 , B0 , BC 58900 latex cast of dorsal interior and dorsal internal mould, Locality 2401; H0 , BC 58879, ventral internal mould, Locality 1835. C0 , D0 , Dulankarella? sp., Locality 593; NMW 2001.38G.467, ventral valve exterior and side view. Scale bars 2 mm.

718

L. E. Popov and L. R. M. Cocks € Family Leptestiidae Opik, 1933 € Genus Leangella (Leangella) Opik, 1933

Type species. Plectambonites scissa var. triangularis Holtedahl, 1916, a subspecies of Leptaena scissa Davidson, 1871, revised by Cocks (1970). Leangella (Leangella) aff. paletsae Popov & Cocks, 2006 (Fig. 15A, B)

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Material. Akdombak Formation. Locality 3136, dorsal internal mould, BC 58702. Remarks. A single dorsal valve shows distinct similarity to Leangella (Leangella) paletsae Popov & Cocks, 2006, from the Dulankara Formation (Early Katian) of the ChuIli Terrane, in having a bifurcating dorsal septum, which extends far beyond the anterior boundary of the divided bema, but differs in having a row of septules between the outer end of the rim bounding the bema and the cardinal extremities. It may represent a new, closely related taxon, but the material is not sufficient for its formal definition. Leangella (Leangella) bakanasensis sp. nov. (Figs 15C–H, 17G) Derivation of name. After the River Bakanas near the type locality. Holotype. BC 58713, a dorsal internal mould (Fig. 15F, G), from the uppermost Katian part of the Akdombak Formation at Locality 2083. Paratypes. Locality 2083 (Mid Katian), one pair of conjoined valves, BC 58739, six ventral internal moulds, BC 58712 (Fig. 15E), BC 58740, NMW 2001.38G.483,

485–488, two ventral external moulds, BC 58864, NMW 2001.38G.489, one dorsal external mould and attached interareas of both valves, BC 58866 (Fig. 17G), one dorsal external mould, NMW 2001.38G.484 (Fig. 15H), two dorsal internal moulds; BC 58714 (Fig. 15C), BC 58862 (Fig. 15F, 17G); Locality 1560, ventral valve, BC 58827. Diagnosis. Leangella lacking a ventral median septum, but with a relatively small ventral muscle field, with each diductor muscle subcircular and surrounded by entire but relatively weak muscle bounding ridges. Bema with a pair of characteristic sharply angular anterior ends extending to two-thirds valve length. Diaphragm relatively weak, particularly anteriorly. Description. Shell concavoconvex, transverse, semioval in outline about two-thirds long as wide, with maximum width slightly anterior to the hinge line. Cardinal extremities rounded. Anterior commissure rectimarginate. Ventral valve lateral profile strongly and evenly convex. Ventral interarea almost orthocline with a small apical pseudodeltidium. Dorsal valve moderately concave with a linear interarea. Chilidial plates small, discrete. Radial ornament finely and unevenly parvicostellate with 2–5 parvicostellae between accentuated ribs and up to 10 parvicostellae per mm along the anterior margin of mature specimens. Ventral interior with small, transverse teeth lacking dental plates. Ventral muscle field small, about one-quarter as long as the valve, bilobed, well-defined by muscle bounding ridges and bisected by a short median ridge. Adductor scars small, confined to the umbo. Subperipheral rim accentuated by minute septules along the lateral and anterior valve margins. Ventral mantle canal system saccate, with long, straight, widely divergent vascula media. Dorsal interior with an erect, trifid cardinal

Figure 15. A, B, Leangella (Leangella) aff. paletsae Popov & Cocks, 2006, Locality 3136, BC 58702, ventral internal mould and latex cast of interior. C–H, Leangella (Leangella) bakanasensis sp. nov., Locality 2083 (late Katian); C, BC 58714, dorsal internal mould; D, NMW 2001.38G.483, ventral internal mould; E, BC 58712, ventral internal mould; F, G, BC 58713, latex cast of dorsal interior and dorsal internal mould; H, NMW 2001.38G.484, dorsal external mould. F, BC 58862, latex cast of dorsal internal mould. Scale bars 2 mm.

Late Ordovician brachiopods

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process and short, widely divergent socket ridges. Bema small, bilobed, surrounded anteromedially by a highly elevated diaphragm. A row of septules between the bema and the cardinal extremities occurs in some specimens. Remarks. Leangella (Leangella) bakanasensis differs from Leangella (L.) paletsae Popov & Cocks, 2006, which is the only other species of the genus reported from the Upper Ordovician of Kazakhstan, in having a small bema bounded by a high diaphragm and in the complete absence of a dorsal median ridge. There are, however, several other Leangella species of Katian age; for example, L. (L.) cylindrica (Reed, 1917) and L. (L.) discuneata Lamont (1935), both revised by Harper (1989); L. (L.) cf. gibbosa (Winchell & Schuchert, 1892), revised by Hiller (1980), from Powys, and L. (L.) sholeshookensis (Jones, 1928), revised by Cocks (2014), from Pembrokeshire, both in Avalonia. The genus has not been reported from the Katian of Baltica or Siberia. L. (L.) cylindrica and L. (L.) gibbosa both have ventral median septa (considered by some authors, but not Cocks & Rong (2000), as characteristic of Diambonia). L. (L.) sholeshookensis has a much more rounded bilobed bema than L. (L.) bakanasansis. Unfortunately, the interiors of L. (L.) cylindrica are unknown, but it is a small species. On the Mediterranean margins of Gondwana the genus is known only from the Late Katian and is represented by two species: L. (L.) anaclyta Havlıcek, 1981 from Montagne Noire and the Iberian Chains (Villas, 1985), and L. (L.) fecunda Villas & Harper in Villas et al., 2002 from Sardinia (Leone et al. 1991). Family Xenambonitidae Cooper, 1956 Subfamily Aegiromeninae Havlıcek, 1961 Genus Chonetoidea Jones, 1928 Type species. Plectambonites papillosa Reed, 1905, from the Slade and Redhill Mudstone Formation (Late Katian) of Pembrokeshire, Wales, a junior synonym of Chonetes  radiatulus Barrande, 1879, from the Kraluv Dvur Formation (Late Katian) of Bohemia, Czech Republic. Chonetoidea enbektenensis sp. nov. (Fig. 16P, R–A0 ) Derivation of name. After the ruins of Enbekten near the type locality. Holotype. BC 60210 dorsal internal mould (Fig. 16Z), from the Hirnantian? part of the Akdombak Formation at Locality 2081. Paratypes. Hirnantian: Locality 43; one ventral internal mould, BC 58807, one dorsal internal mould, BC 58876, one ventral external mould, NMW 2001.38G.491, one dorsal external mould, NMW 2001.38G.492 9 (Fig. 16S); Locality 2080, 7 exteriors, BC 58778 (L 7.9, W 14.8), BC

719

60262–66, two ventral internal moulds, BC 58697, BC 58838, six dorsal internal moulds, BC 58697, BC 58717, BC 58719, BC 58835, BC 58836 (Fig. 16Y), BC 58837 (Fig. 16T); Locality 2081, a pair of conjoined valves, BC 58676, four ventral valves, BC 58673, BC 58683–85, one dorsal valve, BC 58675, two ventral internal moulds, BC 58878b, one dorsal external mould with attached ventral interarea, BC58605 (Fig. 16P); Locality 2062, three external moulds of conjoined valves, NMW 2001.38G.490.1–3, four external moulds, NMW 2001.38G.490.4–5, NMW 2001.38G.490.6, BC 60224 (Fig. 16P) BC 60225 (Fig. 16U). Diagnosis. Shell gently concavoconvex, with transverse profile of the ventral valve strongly curved in the anterior one-third. Radial ornament multicostellate, becoming weakly parvicostellate close to the outer shell margins, with 10–11 ribs per mm. Dorsal interior with a long, blade-like dorsal median septum, and numerous small, radially arranged septules outside the adductor muscle field. Description. Shell gently concavoconvex, transverse, semioval in outline with maximum width at the hinge line. Cardinal extremities almost right angled. Anterior commissure rectimarginate. Ventral valve profile gently to moderately convex, more strongly curved in the anterior one-third, but not geniculate. Ventral interarea low, planar, strongly apsacline, with small, triangular delthyrium covered apically by a minute pseudodeltidium. Dorsal valve weakly concave with a linear, catacline to slightly hypercline interarea. Notothyrium partly covered by small, separated chilidial plates. Radial ornament almost multicostellate posterior to mid-length, becoming weakly parvicostellate towards the anterior margin with 1–5 parvicostellae intervening between accentuated ribs and with 10–11 parvicostellae per mm along the anterior margin including 3–5 accentuated ribs. Concentric ornament of very fine densely spaced, regular fila. Ventral interior with small teeth and incipient dental plates. Muscle field bilobed, open anteriorly, varying from a third to a quarter valve length, bisected by a short median ridge. Dorsal interior with an undercut cardinal process merged with almost straight, widely divergent muscle bounding ridges. Dorsal median septum thin, blade-like, originating at some distance from the posterior margin, variable in length, but usually not exceeding one quarter valve length from the anterior margin. Dorsal adductor muscle field subquadrangular, extending anteriorly to mid-valve, with radially arranged adductor muscle scars, may be bounded by faint muscle bounding ridges in mature specimens. Outside the adductor muscle field there are numerous small, radially arranged septules. Remarks. Chonetoidea enbektenensis differs from C. radiatula (Barrande, 1879) and its possible junior

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720 L. E. Popov and L. R. M. Cocks

Late Ordovician brachiopods 

synonym C. tenerrima Havlıcek, 1967, from the Kraluv  Dvur Formation (Late Katian) of the Czech Republic, in having numerous, small septules covering all of the inner surface of the dorsal valve outside the muscle field, a long, blade-like dorsal median septum and parvicostellate, not multicostellate radial ornament. Candela (2011) has revised the genus and reviewed its relationship with the closely related Sericoidea. Family Hesperomenidae Cooper, 1956

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Remarks. Cocks (2013) transferred the genus Zhilgyzambonites Popov, Cocks & Nikitin, 2002, from the Anderken Formation (Sandbian) of the Chu-Ili Terrane, from Sowerbyellidae to Hesperomenidae. Diambonioidea is also transferred to this family from Grorudiidae here (see below). Genus Anoptambonites Williams, 1962 Type species. Leptaena grayae Davidson, 1883, from the Craighead Limestone (Early Katian) of Girvan, Scotland. Anoptambonites sp. 1 (Fig. 17W, X, A0 ) Material. Locality 8506 (Mid Katian), conjoined valves, BC 58778, ventral internal mould, BC 58777 (L 8.0, W 7.9; Fig. 17X), dorsal external moulds, BC 58779, NMW 2001.38G.502 (Fig. 17A0 , dorsal internal mould, NMW 2001.38G.501 (Fig. 17W). Remarks. The specimens are too poorly preserved to identify precisely, but in the absence of dental plates and in having a planar, slightly concavoconvex shell with unequally parvicostellate radial ornament, a small bilobed ventral muscle field, undercut cardinal process and a large lophophore platform bounded by a thin diaphragm and bisected by a faint median ridge, they resemble Anoptambonites kovalevskii Popov, Nikitin & Cocks, 2000, from the Otar and Degeres members of the Dulankara Formation in the Chu-Ili Terrane of southern Kazakhstan.

721 Anoptambonites? sp. 2 (Fig. 17Y, Z)

Material. Locality 593 (Mid Katian), conjoined valves, NMW 2001.38G.470 (L 10.2, W>12.7, T 5.3; Fig. 17Z); Locality 3136 (Mid Katian), dorsal internal mould, NMW 2001.38G.469 (L 8.3, W 11.2, Sl 4.4; Fig. 17Y). Description. Shell strongly concavoconvex, slightly transverse, semioval outline with maximum width at hinge line. Cardinal extremities slightly acute; anterior commissure rectimarginate. Ventral valve strongly and evenly convex. Ventral inerarea low, planar, apsacline, with narrow, open delthyrium. Dorsal valve moderately convex, more strongly depressed in posterior half. Dorsal interarea low, slightly anacline. Radial ornament unequally and finely parvicostellate, with up to 20 parvicostellae per 3 mm along the anterior margin and 2–4 parvicostellae between accentuated ribs. Ventral interior not observed. Dorsal interior with an undercut cardinal process, small, widely divergent socket ridges and lophophore platform bounded by high, thin diaphragm. Dorsal median septum thin, extending slightly anterior to midlength and merging with diaphragm. A pair of widely divergent ridges dividing both sides of lophophore platform into two almost equal sectors. A strong subperipheral rim present at about half way between the lophophore platform and the shell margin. Remarks. In having a lophophore platform crossed by the median septum and a pair of widely divergent ridges and a well-defined subperipheral rim, in addition to a diaphragm bounding the lophophore platform, the dorsal interior of these shells somewhat resembles Rongambonites Zhan & Cocks, 1998, but differs significantly in having a semioval (but not subtriangular) lophophore platform. Genus Diambonioidea Zeng, 1987 Type species. Diambonioidea transversa Zeng, 1987, from the Miaopo Formation (Sandbian) of Hubei Province, China.

J————————————————————————————————————————— Figure 16. A–O, Q, Kozlowskites botobaicus sp. nov.; A, N, BC 60257, dorsal internal mould and latex cast of dorsal interior, Locality 2080; B, BC 58843, ventral internal mould, Locality 2080; C, D, BC 58842, holotype, ventral and posterior views of ventral internal mould, Locality 2080; E, BC 58722, dorsal internal mould, Locality 2080; F, J, BC58845, ventral and posterior views of conjoined valves, Locality 2080; G, H, BC 60324, ventral exterior, lateral view, Locality 2081; I, BC 60326, dorsal internal mould, Locality 2081; K, L, O, BC 60327, lateral and posterior views of ventral exterior, Locality 2081; M, BC 60328, ventral exterior, Locality 2081; Q, BC 60325, dorsal view of conjoined valves, latex cast, Locality 43. P, R–A0 , Chonetoidea enbektenensis sp. nov.; P, BC 60224a, dorsal view of conjoined valves, latex cast, Locality 2062; R, BC 60224, ventral internal mould, Locality 6022; S, NMW 2001.38G.492, latex cast of dorsal exterior, Locality 43; T, BC 58837, dorsal internal mould, Locality 2080; U, BC 60225, latex cast of ventral exterior, Locality 2062; V, BC 58835a, latex cast of dorsal exterior, Locality 2081; W, BC 60321, latex cast of ventral exterior, Locality 2062; X, BC 58683, dorsal internal mould, Locality 2081; Y, BC 58836, dorsal internal mould, Locality 2080; Z, BC 60210a, holotype, latex cast of dorsal internal mould, Locality 2081; A0 , BC 60322, internal moulds of both valves, Locality 2062. B0 , Enbektenorthis molesta sp. nov., Locality 2088, NMW 2001.38G.796, ventral internal mould. Scale bars 2 mm.

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722 L. E. Popov and L. R. M. Cocks

Late Ordovician brachiopods Remarks. On attributing the new species koknaiensis to Diambonioidea, the familial position of that genus can now be reviewed. It is clear that, because the original material of the type species Diambonioidea transversa Zeng, 1987, is somewhat poorly preserved, Cocks & Rong (1989, 2000) did not appreciate that its cardinal process is undercut and thus placed the genus within Grorudiidae. We therefore here transfer Diambonioidea to Hesperomenidae. Diambonioidea koknaiensis sp. nov. (Figs 13W, 14V–Z)

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Derivation of name. After Koknai Stream, east of the type locality. Holotype. BC 58859, dorsal internal mould (L 3.8, W 9.0, Ml 1.6, Sl 3.0) (Fig. 14X, Y), from the uppermost Katian part of the Akdombak Formation at Locality 2083. Paratypes. Locality 2083 (Late Katian), ventral internal mould, BC 58738 (Fig. 13W), dorsal internal mould, BC 58716 (L 5.0, W 9.2, Ml 1.7, Sl 3.2) (Fig. 14V), two ventral external moulds, BC 58863 (Fig. 14Z) and BC 58865; Locality 2088 (Late Katian), one pair of conjoined valves, NMW 2001.38G.795. Diagnosis. Diambonioidea with planoconvex shell, multicostellate radial ornament and a small bema less than half as long as the platform. Description. Shell flattened, almost planoconvex, strongly transverse, about twice as wide as long, with maximum width at hinge line; cardinal extremities slightly acute. Anterior commissure rectimarginate. Ventral valve gently convex with sagittal profile more strongly curved in anterior one-third valve length. Ventral interarea low, planar, anacline with the delthyrium covered apically by a minute pseudodeltidium. Dorsal valve almost flat with a linear, anacline interarea. Radial ornament almost equally multicostellate with up to 6 ribs per mm. Concentric ornament of very fine, evenly spaced fila.

723

Ventral interior with minute teeth lacking dental plates and a small, gently impressed, bilobed muscle field bisected by a faint median ridge and occupying slightly less than one-quarter valve length. Dorsal interior with undercut cardinal process merged with narrow, transverse socket ridges. Dorsal adductor muscle field on elevated bema, about 35–40% as long as the valve. Radially arranged adductor muscle scars separated by a pair of short, side septa terminating at margins of the bema. Median septum prominent, merged anteriorly with the rim bounding the platform. Remarks. Diambonioidea koknaiensis is closely similar to D. transversa Zeng, 1987, which is the type and only other known species of the genus, in having a raised bema and prominent dorsal median ridge extending anteriorly toward the platform margin, but differs in having almost equally multicostellate (and not unequally parvicostellate) radial ornament, a flat dorsal valve and a shorter length of a bema, which terminates at less than half the distance to the platform, whilst in the Chinese specimens it is at just over half that length. Genus Kassinella Borissiak, 1956 Type species. Kassinella globosa Borissiak, 1956, from the Late Ordovician of the Dulygaly-Zhilchik River, Ulutau, Central Kazakhstan. Kassinella globosa Borissiak, 1956 (Fig. 17K–N) 1956 Kassinella globosa Borissiak: 51, pl. 12, figs 1–7. 1986 Kassinella globosa Borissiak; Misius: 157, pl. 12, figs 1–9. Holotype. CNIGR 1/9131 from the Upper Ordovician (probably Early Katian Dulygaly Formation) of the River Dulygaly-Zhilchik, Ulutau Range, Central Kazakhstan.

J————————————————————————————————————————— Figure 17. A–F, H–J, Kassinella kasbalensis sp. nov.; A, I, BC 60240a, dorsal internal mould, Locality 85244; B, C, BC 58704, dorsal internal mould and latex cast of dorsal interior, Locality 3114; D, BC 58706, ventral internal mould, Locality 3114; E, F, BC 58707, holotype, internal moulds of disarticulated valves and latex cast of dorsal and ventral interiors, Locality 43; H, BC 58866, latex cast of external mould of conjoined valves showing interarea, Locality 3086; J, BC 58708, latex cast of conjoined valves, Locality 3086. G, Leangella (Leangella) bakanasensis sp. nov., Locality 2083, Late Katian, BC 58866, dorsal view of conjoined valves, latex cast. K–N, Kassinella globosa Borissiak, 1956, Dulygalinskaya Formation, Dulygaly-Zhilchik River, Ulutau (paratypes); K, L, CNIGR 7/9131, latex casts of interiors and internal moulds of disarticulated shell; M, CNIGR 6/9131, latex cast of dorsal valve interior; N, CNIGR 5/ 9131, latex cast of dorsal valve exterior. O–V, Kassinella tchingisensis Klenina, 1984, Locality 1833; O, S, NMW 2001.38G.493, dorsal internal mould and latex cast of interior; P, BC 60238, latex cast of ventral exterior; Q, T, BC 60236, latex cast of ventral exterior; R, BC 60239, ventral internal mould; U, BC 60234, dorsal view of latex cast of conjoined valves; V, BC 60235, latex cast of dorsal exterior. W, X, A0 , Anoptambonites sp. 1, Locality 8506; W, NMW 2001.38G.501, incomplete dorsal internal mould; X, BC 58777, ventral internal mould of juvenile specimen; A0 , NMW 2001.38G.502, dorsal external mould. Y, Z, Anoptambonites? sp. 2; Y, NMW 2001.38G.469, dorsal valve interior, Locality 3136; Z, NMW 2001.38G.470, ventral valve exterior, Locality 593. Scale bars are 2 mm.

724

L. E. Popov and L. R. M. Cocks

Paratypes. Dorsal and ventral external moulds of conjoined valves, CNIGR 3a, b/9131; three ventral external moulds CNIGR 2, 4, 5/9131 (Fig. 17N); dorsal external mould CNIGR 6/9131 (Fig. 17M); dorsal and ventral internal moulds of disarticulated shell, CNIGR 7/9131 (Fig. 17K, L).

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Remarks. Data on the type locality and horizon for Kassinella globosa are inadequate; however, the type specimens probably came from the Dulygaly Formation, dated as Early Katian (Nikitin 1972). Misius (1986) redescribed Kassinella globosa, mostly using specimens from the Ichkebash Formation (Early Katian) of the Dzhebgly Mountains, Southern Kazakhstan. In spite of poor illustrations, Misius’ description of these specimens leaves little doubt that they are conspecific with the shells originally described by Borissiak (1956). Kassinella kasbalensis sp. nov. (Fig. 13V, 17A–F, H–J) Derivation of name. After Kasbala River, near the type locality. Holotype. BC 58707 (Fig. 17E, F), internal moulds of disarticulated conjoined valves, from the Akdombak Formation (Late Katian), Locality 45 east side of River Zhanybek river, about 3.2 km west of Akdombak Mountain. Paratypes. Locality 45 (Late Katian) (topotypes), external moulds of conjoined valves, BC 58708 (Fig. 17J), Locality 256 (Late Katian), one ventral internal mould of juvenile specimen, NMW 2001.38G.771; Locality 3086 (Late Katian), BC 58866 (Fig. 17H), internal mould of conjoined valves, BC 58709, external mould of dorsal valve and attached ventral interarea, BC 58708 (Fig. 17J), dorsal internal mould, BC 58710; Locality 3114, two dorsal internal moulds, BC 58704 (Fig. 17B–C), BC 58705, ventral internal mould, BC 58706 (Fig. 17D); Locality 3126, ventral internal mould of juvenile, NMW 2001.38G.782. Diagnosis. Shell gently concavoconvex, about two thirds as long as wide. Radial ornament parvicostellate with 5–7 parvicostellae between accentuated ribs and 12–14 parvicostellae per mm. Ventral interior with a small, bilobed strongly impressed muscle field and well-defined subperipheral rim, accentuated by a row of radially arranged pustules. Dorsal interior with high, subtriangular median septum. Lophophore platform bounded by a high diaphragm almost orthogonal to the valve surface. Subperipheral rim strong, ridge-like, at about half the distance between the platform and the shell margin. Description. Shell gently concavoconvex to almost planoconvex, transverse and semioval in outline, about twothirds as long as wide, with maximum width at hinge line.

Cardinal extremities slightly acute to almost rectangular. Anterior commissure rectimarginate. Ventral valve evenly convex with low apsacline interarea and a narrow delthyrium completely covered by a convex pseudodeltidium. Dorsal valve weakly concave to almost flat, with an anacline, linear interarea and discrete chilidial plates. Radial ornament weakly parvicostellate, with 5–7 parvicostellae between accentuated ribs and 12–14 parvicostellae per mm at the anterior margin of mature specimens. Ventral interior with small teeth lacking dental plates. Small, bilobed, ventral muscle field strongly impressed, bisected by prominent median ridge. Adductor scars small, located in the umbonal area and completely enclosed by the diductors. Two prominent swellings in front of the hinge line at about halfway between the umbo and cardinal extremities. Ventral subperipheral rim well defined, accentuated by a row of small radially arranged pustules. Ventral mantle canals saccate with long, divergent vascula media. Dorsal interior with trifid, undercut cardinal process and short, slightly curved socket ridges almost parallel to the hinge line. Median septum strong, high, subtriangular. Lophophore platform semicircular in outline, between two-thirds and three-quarters as long as wide and about 70% as long as the valve, bounded by a high diaphragm almost orthogonal to the almost orthogonal to the valve surface. Posterolateral terminations of diaphragm merge with thick swellings situated approximately opposite to those in the ventral valve. Strong, ridge-like subperipheral rim at about half the distance between the platform and the shell margin. Remarks. This species differs from the type species Kassinella globosa and from K. shiyangensis Zhan & Cocks, 1998, from the Changwu Formation (Katian) of South China, in its smaller lophophore platform bounded by a very high rim almost orthogonal to the shell surface, and in having a second strong dorsal subperipheral rim. In the ventral valve of K. globosa, a weakly defined subperipheral rim is mainly accentuated by a concentric row of the papillae, whereas in K. kasbalensis the ventral subperipheral rim is ridge-like and the papillae are more pronounced. K. kasbalensis differs from K. tchingisensis Klenina, 1984, from the Taldyboi Formation (Early Katian) of the Chingiz Range, in being about twice the size and in having a stronger dorsal median septum, a diaphragm bounding the lophophore platform, and a strong, ridge-like dorsal subperipheral rim. Kassinella tchingisensis Klenina, 1984 (Fig. 17O–V) 1984 Kassinella tchingisensis Klenina: 87, pl. 8, figs 1–6. 1984 Kassinella nana (Borissiak MS) Klenina: pl. 7, figs 1, 10, pl. 8, figs 20–27 (nomen nudum).

Late Ordovician brachiopods Holotype. IGNA 411/123, ventral valve from Locality 603 of Klenina (1984), upper part of the Taldyboi Formation (Katian), tbIII beds of Nikitin (1972, fig. 66), west side of the River Taldyboi, Chingiz Range.

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Material. Locality 1833, conjoined valves, BC 60233, BC 60234 (Fig. 17P), ventral valves, BC 60237, BC 60236 (Fig. 17Q), dorsal external mould with ventral interarea, BC 60239 (Fig. 17R), dorsal valves, BC 60235 (Fig. 17V), BC 60236 (Fig. 17T); dorsal internal mould, NMW 2001.38G.493 (Fig. 17O, S). Remarks. This species differs from Kassinella kasbalensis sp. nov. and K. anisa Percival, 1979, in having a relatively small, gently concavoconvex and strongly transverse shell with acute cardinal extremities. It also has a dorsal diaphragm inclined obliquely anteriorly to the valve floor, and less prominent subperipheral rims in both valves, unlike both K. kasbalensis and K. anisa. There is confusion in Klenina’s (1984) original publication, since specimens from two different horizons within the Taldyboi Formation were described as Kassinella tchingisensis. The first set came from Unit TB9 in the middle part of the Taldyboi Formation and were illustrated by Klenina (1984) as Kassinella nana Borissiak (a name never published by M. A. Borissiak), and are from the same horizon as specimens in our collection. They show the characteristic features of Kassinella. We therefore preserve the binomen Kassinella tchingisensis for those shells, which also include the specimens illustrated as Kassinella nana by Klenina, since that taxon was not formally described and is therefore a nomen nudum, and there is reference to those illustrations in the original description of K. tchingisensis by Klenina (1984, p. 87). The second taxon described under the same binomen from another horizon within the upper Taldyboi Formation must be considered as a junior homonym of K. tchingisensis, since, according to the original description by Klenina (1984), it has the characteristic features of Kassinella; however, no adequate illustrations of the dorsal and ventral valve interiors were given. If these shells indeed belong to Kassinella they are probably conspecific with K. tchingisensis as redefined here. € Family Sowerbyellidae Opik, 1930 Genus Kozlowskites Havlıcek, 1952 Type species. Strophomena nuntia Barrande, 1879, from  the Kraluv Dvur Formation (Late Katian) of Bohemia, Czech Republic. Remarks. Cocks (2013) has discussed Kozlowskites and its relationships to other genera within Sowerbyellidae, particularly Anisopleurella Cooper, 1956, and concluded that the latter genus was confined to rocks of Darriwilian and Early Sandbian age, and that the species of Katian

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and Hirnantian age formerly placed within Anisopleurella, such as A. novemcostata Nikitin, 1980, from the Zhalair Formation (Hirnantian) of the Chu-Ili Range, Kazakhstan, are better placed within Kozlowskites. Kozlowskites botobaicus sp. nov. (Fig. 16A–O, Q) Derivation of name. After Botobai stream near the type locality. Holotype. BC 58842 (Fig. 16C, D), ventral internal mould from Locality 2080, on the right-hand side of the River Tolen, Chingiz Range, uppermost Akdombak Formation (Hirnantian). Paratypes. Hirnantian, Locality 2080, conjoined valves BC 58723, ventral valves, BC 58694, BC 58696, BC 58727, BC 58729, BC 58843 (Fig. 16B), BC 58844–46, BC 60259–61, dorsal valves, BC 58722 (Fig. 16E), BC 58724–26, BC 58728, BC 60257 (Fig. 16A, N), BC 60258; Locality 2081, conjoined valves, BC 60325 (Fig. 16Q), BC 80326 (Fig. 16I), ventral valves, BC 58680–81, BC 60323, BC 60324 (Fig. 16G, H), BC 60327 (Fig. 16K, L, O), BC 60328 (Fig. 16M), dorsal internal mould, BC 58682; Locality 43, conjoined valves, BC 60325 (Fig. 16Q). BC 60268, ventral valve, BC 60267. Diagnosis. Shell strongly concavoconvex, transverse, subtriangular to semioval. Ventral valve strongly curved in umbonal region. Radial ornament finely parvicostellate with three accentuated ribs originating at the umbo and 10–14 parvicostellae per mm along the anterior margin. Ventral muscle field bilobed, gently impressed, surrounded laterally by muscle bounding ridges. Ventral interior with bema extending slightly anteriorly beyond the mid-valve and strong, blade-like outer side septa. Description. Shell strongly concavoconvex, transverse, semioval to subtriangular in outline, with maximum width at hinge line. Cardinal extremities acute and may be slightly alate. Anterior commissure rectimarginate. Sagittal profile of the ventral valve almost semicircular, more strongly curved posterior to mid-length. Umbonal region swollen. Ventral interarea low, anacline, with a small, triangular delthyrium covered apically by a pseudodeltidium. Dorsal valve strongly concave with low, hypercline interarea and small separated chilidial plates. Radial ornament finely parvicostellate with 10–14 parvicostellae per mm along the anterior margin of mature specimens. Three accentuated ribs diverge from the umbo. Four to 6 secondary accentuated ribs appear along the anterior margin in larger specimens. Ventral interior with small, transverse teeth lacking dental plates. Ventral muscle field small, strongly bilobed, less than one-fifth valve length, bisected medially by a short median ridge and faint muscle bounding ridges along its lateral sides. Mantle canals

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lemniscate, with long, straight, widely divergent vascula media confluent with accentuated ribs on the shell surface. Dorsal interior with undercut cardinal process merged with short, almost straight, widely divergent socket ridges. Bema bilobed, bordered by a rim. Median septum thin, originating at some distance from the posterior margin and slightly shorter than the bema. Two pairs of side septa with the outer side septa high, prominent and blade-like. Remarks. The new species differs from Kozlowskites nuntius (Barrande), the type species of the genus redescribed by Cocks (2013), in having a larger bema and longer side septa extending to the mid-valve, and in radial ornament with three accentuated ribs on the ventral valve. Kozlowskites botobaicus shows a distinct similarity to K. gracilis (Jones, 1928) from the Haverford Mudstone Formation (Hirnantian to Rhuddanian) of Wales (as revised by Cocks 1970, 2014; Temple, 1970) in general shell shape, characters of radial ornament and strong development of side septa, but can be distinguished in having a ventral median ridge and a gently impressed ventral muscle field with distinct muscle bounding ridges. K. botobaicus differs from the approximately contemporaneous K. novemcostatus (Nikitin in Nikitin et al., 1980), from the Zhalair Formation (Hirnantian) of the Chu-Ili Range, southern Kazakhstan, in having a well-defined ventral muscle field, shorter bema and outer side septa, finer radial ornament with 10–14 parvicostellae per mm (instead of seven in K. novemcostatus) and a strongly convex ventral valve sagittal profile and swollen umbonal area. In comparison to K. ovalifera (Havlıcek, 1967),   from the Kraluv Dvur Formation (Late Katian) of the Czech Republic, K. botobaicus can be easily distinguished in having a larger bema and longer side septa extending to the mid-valve, and a strongly concavoconvex profile.

727 Olgambonites? sp. (Fig. 13X)

Remarks. A well-preserved ventral valve internal mould, BC 58703 (Fig. 13X) (L 7.4, W 13.7), from the Akdombak Formation (Mid Katian) of Locality 3114, bears a great resemblance to Olgambonites, particularly in its resupination near the valve margin. However, it has a pair of short dental plates, which are lacking in the type and only known species of Olgambonites. Final assessment must await the discovery of dorsal interiors and also knowledge of the exteriors of both valves. Another ventral internal mould, BC 58711 (L 5.7, W 10.6), from the Late Katian part of the Akdombak Formation at Locality 2083, also has the characteristic resupination and interior features of the type species, but specific confirmation must await discovery of dorsal interiors. The genus itself appears to be endemic to the Kazakh terranes. Genus Sowerbyella (Sowerbyella) Jones, 1928 Type species. Leptaena sericea J. de C. Sowerby, 1839, from the Alternata Limestone Formation (Early Katian) of the type Caradoc area, Shropshire, England. Sowerbyella (Sowerbyella) akdombakensis Klenina, 1984 (Fig. 18D, E, J, K) 1984 Sowerbyella (Sowerbyella) akdombakensis Klenina: 82, pl. 7, figs 12, 15, 17, 19, 20, pl. 9, figs 2, 3. 2000 Sowerbyella (Sowerbyella) akdombakensis Klenina; Popov et al.: 855, pl. 4, figs 1–6. 2006 Sowerbyella (Sowerbyella) akdombakensis Klenina; Popov & Cocks: 270, pl. 5, figs 13, 14.

Genus Olgambonites Popov, Cocks & Nikitin, 2002

Holotype. IGNA 411/172, a ventral valve, from the Katian part of the Akdombak Formation, Locality 1859, the same as Locality 800 of Klenina (1984).

Type species. Olgambonites insolita Popov, Cocks & Nikitin, 2002, from the Anderken Formation (Sandbian) of Chu-Ili Range, Kazakhstan.

New material. Locality 1859 (topotypes), conjoined valves, BC 59256, 19 ventral valves, BC 59257–60, NMW 2001.38G.8–10, NMW 2001.38G.457.1–5, 458.1–5,

J————————————————————————————————————————— Figure 18. A–C, F, G, I, Sowerbyella (Sowerbyella) intricata Nikiforova, 1978; A, BC 58821, latex cast of dorsal interior, Locality 1053; B, BC 58822, latex cast of dorsal internal mould, Locality 1053; C, NMW 2001.38G.503.1, ventral internal mould; F, BC 60292, latexes of dorsal interior, Locality 1053; G, BC 60292, dorsal internal mould, Locality 1053; I, NMW 2001.38G.476, latex cast of dorsal exterior, Locality 1055. D, E, J, K, Sowerbyella (Sowerbyella) akdombakensis Klenina, 1984; D, BC 58818, ventral internal mould, Locality 3115; E, BC 58815, ventral internal mould, Locality 3115; J, NMW 2001.38G.519, latex cast of dorsal interior, Locality 3115; K, NMW 2001.38G.697, ventral exterior, Locality 1859. H, L–U, Sowerbyella (Sowerbyella) papiliuncula Borissiak, 1972; Locality 1830; H, NMW 2001.38G.536, ventral internal mould; L, NMW 2001.38G.520, latex cast of dorsal interior, Locality 2423; M, NMW 2001.38G.523, dorsal view of conjoined valves, latex cast, Locality 2423; N, NMW 2001.38G.525, dorsal view of conjoined valves, latex cast; O, NMW 2001.38G.521, dorsal internal mould, Locality 1830; P, NMW 2001.38G.527, latex cast of ventral exterior, Locality 2423; Q, NMW 2001.38G.522, ventral exterior; R, NMW 2001.38G.733, dorsal internal mould, Locality 2423; S, NMW 2001.38G.534.1, ventral internal mould; T, NMW 2001.38G.529, dorsal view of conjoined valves, latex cast, Locality 2423; U, NMW 2001.38G530, ventral internal mould, Locality 1858. Scale bars 2 mm.

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697 (Fig. 18K), 734, two dorsal valves, BC 59261, NMW 2001.38G.7, three dorsal external moulds, NMW 2001.38G.457.6–8; Locality 1830, conjoined valves BC 59262–67, ventral internal moulds BC 59268–75, dorsal internal moulds BC 59276–79; Locality 3115, one ventral external mould, NMW 2001.38G.223, five dorsal external moulds, BC 58817, BC 58818 (Fig. 18D), BC 58819–20, NMW 2001.38G.236, five ventral internal moulds, BC 58815 (Fig. 18E), NMW 2001.38G.232.1, 233–235, six dorsal interiors, NMW 2001.38G.232.2, BC 58814–16, NMW 2001.38G.224, 519 (Fig. 18J).

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Remarks. Klenina (1984) gave a detailed description of the species, and additional discussion and illustrations are in Popov et al. (2000) and Popov & Cocks (2006). Sowerbyella (Sowerbyella) intricata Nikiforova, 1978 (Fig. 18A–C, F, I)

mantle canals lemniscate with short, straight, divergent vascula media. Dorsal interior with trifid, undercut cardinal process small, thickened, widely divergent socket plates. Bema subtriangular bounded by a well-defined rim. Two pairs of side septa well defined with a stronger inner pair. Faint median septum occasionally seen in mature specimens. Remarks. The specimens are essentially identical to those described by Nikiforova (1978), apart from the occasional development of a relatively faint dorsal median septum. Sowerbyella (Sowerbyella) papiliuncula Borissiak, 1972 (Figs 18H, L–U, 19A–D)

1955 Sowerbyella aff. sericea (Sowerby); Borissiak: 47, pl. 5, figs 1–7. 1978 Sowerbyella intricata Nikiforova: 108, pl. 149, figs 12–20, text-fig. 3.

1972b Sowerbyella papiliunculus Borissiak: 183, pl. 49, figs 4–7. non 1984 Sowerbyella papiliuncula Borissiak; Klenina, p. 81. 1986 Sowerbyella tamdysuensis Misius: 150, pl. 15, figs 1–18, pl. 16, figs 1–6.

Holotype. CNIGR 25/10532, a dorsal valve, from the Archalyk Beds (upper Katian), Locality 69 of Shakhriomon-2 section, Zerafshan Range, Uzbekistan.

Holotype. CNIGR 7/9555, conjoined valves, from Locality 1831, Kulunbulak Formation (Katian) of Kulumbulak River, Tarbagatai Range, Kazakhastan.

Material. Akdombak Formation (Katian) Locality 1053, six ventral internal moulds, NMW 2001.38G.7, NMW 2001.38G.503.1 (Fig. 18C), NMW 2001.38G.504–508; two ventral external moulds NMW 2001.38G.503.2–3, 12 dorsal internal moulds, NMW 2001.38G.509–515, BC 58814, BC 58815 (Fig. 18E), BC 58816–17, BC 58821 (Fig. 18A); Locality 1055, two dorsal internal moulds, NMW 2001.38G.476–477; four dorsal external moulds, NMW 2001.38G.478–479, NMW 2001.38G.516–518. Description. Shell concavoconvex, transverse, semicircular in outline, about three-fifths as long as wide, with maximum width at the hinge line. Cardinal extremities slightly acute to almost rectangular. Anterior commissure rectimarginate. Ventral valve lateral profile moderately convex, with maximum height at mid-length. Ventral interarea low, planar, anacline, with a small, apical pseudodeltidium. Dorsal valve moderately concave with a low, almost catacline interarea, chilidial plates discrete. Radial ornament unequally parvicostellate with 5–6 ribs per mm in mature specimens and 2–5 ribs between accentuated ribs. Ventral interior with small transverse teeth supported by low, divergent dental plates. Muscle field bilobed, defined laterally by ridge-like muscle bounding ridges, about half as long as the valve. Diductor scars large, divergent, divided medially by low ridge originating in front of small, umbonal adductor scars. Ventral

Material. Locality 70, one pair of conjoined valves, NMW 2001.38G.722, three ventral valves, NMW 2001.38G.609–11, one dorsal internal mould, NMW 2001.38G 612; Locality 1830, six external moulds of conjoined valves, NMW 2001.38G.532 (Lv 8.9, Ld 8.2, W 13.8), NMW 2001.38G.533 (Lv 7.6, Ld 6.7, W 13.8), BC 59262–67, 10 ventral valves, NMW 2001.38G.522 (L 5.3, W 8.8), NMW 2001.38G.536 (Fig. 18H), BC 59268–75, five dorsal internal moulds, NMW 2001.38G.521, BC 59276–79; Locality 1835, two pairs of conjoined valves, NMW2001.38G.613, BC 59280, 34 ventral valves, BC 59281–93, NMW 2001.38G.537, 545, 563–574, 723, NMW 2001.38G.538, 540, 543, 724, 730–732, 30 dorsal valves, NMW 2001.38G.544, NMW 2001.38G.541, 547– 562, 575, 728, BC 59294–305 Locality 1858: two ventral internal moulds, NMW 001.38G.530, NMW 2001.38G.531; Locality 2423; three pairs of conjoined valves, NMW 2001.38G.534.1–3, 9 external moulds of conjoined valves NMW 2001.38G.523 (Lv 4.6, Ld 4.3, W 7.0), NMW 2001.38G.524 (Lv 6.6, Ld 6.0, W 9.9), NMW 2001.38G.529 (Lv 9.5, Ld 8.9, W 14.8), NMW 2001.38G.534.11–16); four ventral external moulds, NMW 2001.38G.527 (Lv 5.4, W 10.0), five dorsal valves, NMW 2001.38G.534.8–10; dorsal internal moulds, NMW 2001.38G.520, 733 (Fig. 18R), four dorsal external moulds, NMW 2001.38G.534.4–7 (all early Katian).

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Late Ordovician brachiopods Description. Shell concavoconvex, transverse, semioval in outline, two-thirds as long as wide, with maximum width at the hinge line and slightly acute cardinal extremities. Weakly paraplicate anterior commissure in mature specimens. Ventral valve lateral profile moderately convex, strongly curved in posterior one-third with an incipient ventral median fold flanked by a pair of shallow sulci in mature specimens. Ventral interarea low, planar, anacline, with a small, apical pseudodeltidium. Dorsal valve moderately concave, but more strongly posteriorly to mid-length, with a weak dorsal median fold. Dorsal interarea low, catacline to slightly hypercline, chilidial plates discrete. Radial ornament parvicostellate. Ribs fine, with very narrow interspaces increasing by bifurcation and intercalation, with 10–11 ribs per mm in mature specimens. Concentric ornament of fine, densely spaced fila. Ventral interior with small transverse teeth supported by incipient dental plates continuing anteriorly as straight, divergent muscle bounding ridges. Muscle field flabellate, bisected by a short, high median ridge and with widely divergent diductor scars extending anteriorly to near midlength. Adductor scars, small, linear, deeply impressed in the umbonal area. Mantle canals strongly impressed, with broad and short vascula media branching immediately in front of the muscle scars. Dorsal interior with undercut cardinal process merged with small, straight, widely divergent socket plates. A pair of high, thin slightly divergent side septa terminating at about three-fifths valve length from the posterior margin. Bema and dorsal adductor scars variably impressed, but usually present in fully grown specimens. Remarks. This species was described originally by Borissiak (1972b) from the Taldyboi and Kulunbulak formations. Its diagnostic features include a weakly paraplicate anterior commissure. A weakly defined bema is visible on the illustrated dorsal internal mould (Borissiak 1972b, pl. 49, fig. 4). Klenina (1984) assigned to S. (S.) papiliuncula some specimens from the Taldyboi Formation of the Chingiz Range, which are characterized by a strong ventral sulcus developed in the anterior half of the ventral valve, and a high, flat-topped dorsal median fold (Klenina 1984, pl. 7, figs 3–8). Interiors of neither valve were illustrated and these shells are unlikely to be conspecific with S. (S.) papiliuncula. Specimens from Localities 1831 and 1835 exhibit an incipient ventral median fold and corresponding sulcus on the dorsal valve flanked by sulci, and in our opinion are assignable to Sowerbyella papiliuncula. In the Taldyboi Formation this species tends to form a low-diversity association with Schachriomonia parva. S. (S.) papiliuncula is also a characteristic component of the more diverse faunal association confined to silty bottoms and dominated by Bokotorthis abayi (Localities 1830, 2423), but the Sowerbyella are usually characterized by smaller shell sizes, weakly defined bema and almost

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rectimarginate anterior commissure except for a few larger specimens which exhibit diagnostic features of the species. Shells closely similar to S. (S.) papiliuncula were described by Misius (1986) from the Ichkebash Formation (Early Katian) of the Dzhebagly Mountains in Southern Kazakhstan under the name S. (S.) tamdysuensis Misius, 1986. This taxon is considered here to be a junior synonym of S. (S.) papiliuncula. Order Orthotetida Waagen, 1884 Suborder Triplesiidina Moore, 1952 Superfamily Triplesioidea Schuchert, 1913 Family Triplesiidae Schuchert, 1913 Genus Cliftonia Foerste, 1909 Type species. Cliftonia striata Foerste, 1909, from the Clinton Formation (Llandovery) of Tennessee, USA. Cliftonia sp. (Figs 12B0 , 19J, K) ?1980 Cliftonia sp. 2 Nikitin et al. in Apollonov et al.: p. 46, figs 27, 28. Material. Locality 2080, dorsal external mould BC 60216 (Fig. 12B0 ), dorsal internal mould BC 58852b; Locality 2081, dorsal internal mould BC 60217 (Fig. 19J, K). Remarks. Cliftonia is a relatively common component of the Hirnantian brachiopod faunas elsewhere, but is often represented by only a few specimens and thus described in open nomenclature. All our specimens are incomplete and variably distorted, which makes identification difficult, but they have distinctive irregular ribbing in combination with lamellose concentric ornament and a keeled, forked cardinal process. They resemble the specimens described as Cliftonia sp. 2 by Nikitin et al. in Apollonov et al. (1980) from the Zhalair Formation (Hirnantian) of the Chu-Ili Range in their radial and concentric ornament, as well as in having low, flattened medially dorsal median folds. Genus Grammoplecia Wright & Jaanusson, 1993 Type species. Grammoplecia triplesioides Wright & Jaanusson, 1993, from the Boda Limestone (Late Katian) of Sweden. Grammoplecia subcraegensis (Rukavishnikova, 1956) (Fig. 19I) 1956 Oxoplecia subcraegensis Rukavishnikova: 152, pl. 5, figs 1–3. 1984 Triplesia subcraegensis (Rukavishnikova); Klenina: 60, pl. 15, figs 14, 15, 17.

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Figure 19. A–D, Sowerbyella (Sowerbyella) papiliuncula Borissiak, 1972, Locality 1835; A, NMW 2001.38G.538, ventral internal mould; B, NMW 2001.38G.537, ventral exterior; C, NMW 2001.38G.540, ventral internal mould; D, NMW 2001.38G.539, dorsal view of conjoined valves, latex cast. E–H, Eostropheodonta aff. hirnantensis (M’Coy, 1851), Locality 2080; E, F, BC 58692, dorsal internal mould and latex cast of exterior; G, BC 58693, dorsal internal mould; H, BC 58893, ventral internal mould. I, Grammoplecia subcraegensis (Rukavishnikova, 1956), Locality 2133, BC 60301, ventral internal mould. J, K, Cliftonia sp., Locality 2081, BC 60217, latex cast interior and dorsal internal mould. L, N, O, Bokotorthis abayi (Klenina, 1984); L, NMW 2001.38G.282, dorsal external mould, Locality 1858; N, NMW 2001.38G.465, latex cast of dorsal interior, Locality 70; O, NMW 2001.38G.383, latex cast of ventral interior, Locality 70. M, Schachriomonia parva (Rukavishnikova, 1956), Locality 70, NMW 2001.38G.384, latex cast of ventral exterior. Scale bars 2 mm.

1993 Grammoplecia subcraegensis (Rukavishnikova); Wright & Jaanusson: 104. 2000 Grammoplecia subcraegensis (Rukavishnikova); Popov, Nikitin & Cocks: 852, pl. 1, figs 9–11. Material. Locality 2133, BC 60301, ventral internal mould (Lv 17.1, W 21.9, Sw 12.5). Remarks. The types of Grammoplecia subcraegensis are from the Dulankara Formation of the Chu-Ili Terrane. The

specimens described and illustrated by Klenina (1984) as Triplesia subcraegensis are conspecific with those from Chu-Ili. They occur sporadically in the upper part of the Taldyboi Formation. Order Orthida Schuchert & Cooper, 1932 Superfamily Orthoidea Woodward, 1852 Family Plaesiomyiidae Schuchert, 1913 Genus Bokotorthis Popov, Nikitin & Cocks, 2000

Late Ordovician brachiopods Type species. Schizophorella kasakhstanica Rukavishnikova, 1956, from the Otar Member of the Dulankara Formation (Katian) of the Chu-Ili Range, Kazakhstan. Remarks. Bokotorthis is a very variable genus and is extremely abundant at many localities in both the Chingiz and Chu-Ili terranes, although it has not been found in the Ishim-Selety Region (Nikitin et al. 2006). We have distinguished three species within the Taldyboi and Akdombak formations. Klenina (1984) described four species from the same horizon in the Taldyboi Formation, all of which we consider synonyms of Bokotorthis abayi.

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Bokotorthis abayi (Klenina, 1984) (Figs 19L, N, O, 20Q, S–B0 ) 1984 Plaesiomys (Dinorthis) abayi Klenina: 35, pl. 1, fig. 8, pl. 2, figs 3, 5, 7. 1984 Plaesiomys (Dinorhtis) tschingisensis Klenina: 36, pl. 1, figs 5, 7, 11, 13, pl. 2, figs 2, 4, 6, 9. 1984 Plaesiomys (Dinorhtis) nikitini Klenina: 38, pl. 1, fig. 14, pl. 2, figs 9–14. 1984 Plaesiomys (Dinorthis) distincta Klenina: 39, pl. 1, figs 6, 10, pl. 2, figs 1, 15, 16. Holotype. IGNA 411/24, conjoined valves from Locality 604 of Klenina (1984), upper part of the Taldyboi Formation, by the River Taldyboi. Material. Taldyboi Formation: Locality 70 (Early Katian): one ventral internal mould, NMW 2001.38G.383 (Fig. 19O), one dorsal internal mould, NMW 2001.38G.465 (Fig. 19N); Locality 282 (Early Katian): 10 conjoined valves, NMW 2001.38G.250–269, two ventral valves, NMW 2001.38G.270–271, eight dorsal valves, NMW 2001.38G.273–281; Locality 1830 (Early Katian), 16 conjoined valves, BC 59215–29, 7 ventral valves, BC 59230–36, and 19 dorsal valves, BC 59237–55, one ventral internal mould, NMW 2001.38G.386 (Fig. 20Q, U), three dorsal internal moulds, NMW 2001.38G. 385, 542 (Fig. 20T), 543 (Fig. 20V); Locality 1858 (Early Katian), two conjoined valves, BC 58909, BC 58914, five ventral valves, BC 58915–16, BC 5891819, NMW 2001.38G.701–702, 7 dorsal valves, BC 58917, BC 58920–24, NMW 2001.38G.282 (Fig. 19L); Locality 2423 (Early Katian): three pairs of conjoined valves, NMW 2001.38G.437 (Fig. 20 S, X, Z), 438, 489 (Fig. 20 W, Y, A0 , B0 ), three specimens of both valves, BC 60285– 89. Akdombak Formation. Remarks. Bokotorthis abayi (Klenina, 1984) is probably the most abundant brachiopod in the upper part of the Taldyboi Formation. It was originally assigned by Klenina (1984) to Plaesiomys (Dinorthis), together with three other closely related species, P. (D.) tschinghisensis Klenina, 1984, P. (D.) nikitini Klenina, 1984 and P. (D.)

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distincta Klenina, 1984. All those taxa show characteristic features of Bokotorthis and often occur in the same localities and units, as can be seen from the locality data in Klenina (1984). Thus they probably represent a single but variable species, which should be named B. abayi, as pointed out by Popov et al. (2000). Bokotorthis cf. plicadua (Xu, 1979) (Fig. 20L, M, R) Material. Locality 8506 (Katian), ventral internal moulds, BC 58770 (Fig. 20M), BC 58771 (Fig. 20R), dorsal internal moulds, BC 58772 (Fig. 20L) (Lv 6.3, W 9.0, Ld 5.6. Iw 6.2, T 4.8), BC 58773. Description. Shell dorsibiconvex, transverse, subtrapezoidal in outline with hinge line shorter than maximum valve width, and rounded cardinal extremities. Anterior commissure broadly uniplicate. Ventral valve gently convex, with sulcus becoming prominent anterior to the midlength. Interarea moderately high, triangular, apsacline. Dorsal valve moderately convex, with swollen umbonal area. Radial ornament costate with up to 32 rounded ribs, including up to seven ribs in the central sulcus. Ventral interior with strong teeth, subparallel dental plates, and an elongated, flabellate muscle field. Diductor scars strongly impressed, separated by a shorter and narrow adductor scar on a high ridge elevated anteriorly. Dorsal interior unknown. Remarks. In having a narrow, elongated ventral muscle field, a broad ventral sulcus originating almost at midlength and an undifferentiated dorsal median fold, the Kazakh specimens are most closely similar to Bokotorthis plicadua (Xu, 1979) from the Koumenzi Formation (Katian), China, and are considered here as probably conspecific; however, the strong distortion of the shells makes detailed comparison difficult. Bokotorthis abayi (Klenina, 1984), from the upper part of the Taldyboi Formation (Early Katian) of the Chingiz Range differs in having a ventral sulcus and a dorsal median fold originating in the umbonal area and a broad, subpentagonal ventral muscle field which is almost as long as wide. Bokotorthis minuta sp. nov. (Fig. 20A–K, N–P) Holotype. NMW 2001.38G.42, ventral internal mould (Lv 5.6, W 9.4, Iw 7.0, Ml 3.9, Mw 1.5; Fig. 20F-H) from the Akdombak Formation (Katian), Locality 7875, upper reaches of Bakanas River, Chingiz Range. Paratypes. Locality 7975 (Mid Katian), one dorsal internal mould, NMW 2001.38G.40 (Ld 4.8, W 6.5, Iw 4.6), two dorsal valves, NMW 2001.38G.41 (Ld 4.2, W 5.4), 2001.38G.44 (Fig. 20E, I), ventral valves, NMW 2001.38G.43 (Fig. 20C, D), NMW 2001.38G.215–218. Locality 1560 (Late Katian), one internal mould of

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732 L. E. Popov and L. R. M. Cocks

Late Ordovician brachiopods conjoined valves, BC 58833 (Fig. 20K, O, P), one dorsal external mould, BC 60290 (Fig. 20J, N).

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Diagnosis. Shell small for genus, strongly dorsibiconvex, with broadly uniplicate anterior commissure. Ventral median sulcus and dorsal median fold originating anteriorly to mid-length. Radial ornament with up to 24 ribs including up to five ribs in ventral sulcus and up to six ribs in dorsal median fold. Ventral muscle field large, strongly impressed, more than twice as long as wide, with adductor scars elevated on a high septum. Cardinal process robust, almost completely occupying the notothyrial cavity. Description. Shell slightly dorsibiconvex to subequally biconvex, transverse, suboval, 60–70% as long as wide and about 75% as thick as long. Hinge line 70–75% as wide as the shell; cardinal extremities rounded. Anterior commissure broadly uniplicate. Ventral valve moderately convex, with a shallow sulcus originating anterior to the mid-length and terminating in a high, semioval tongue directed almost orthogonally to the commissural plane. Interarea low, triangular, apsacline. Dorsal valve moderately and evenly convex, with a low median fold originating at mid-length. Dorsal interarea linear, almost orthocline. Radial ornament costate with up to 24 rounded ribs, including up to six on the dorsal median fold and five ribs in the ventral sulcus. Ventral interior with strong teeth supported by subparallel dental plates strongly thickened at the base. Narrow muscle field deeply impressed, more than twice as long as wide, extending to mid-length, the diductor scars completely separated by the adductor scars, which are elevated anteriorly on a high septum. Ventral mantle canal system saccate, with short, divergent vascula media and strongly impressed vascula genitalia. Dorsal interior with low and very narrow notothyrial platform mainly occupied by a bulbous, strongly thickened cardinal process, high, anteriorly directed brachiophores and deep sockets. Dorsal adductor field narrow and deeply impressed posteriorly, extending anteriorly to mid-length and bisected by a faint median ridge which fades anteriorly.

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Remarks. The specimens are almost half the size of other known species of the genus, but they certainly represent adult, fully grown individuals, as is shown by the well-developed characters in the interior in both valves and also the relatively thick shells. They differ from the other Kazakh species of Bokotorthis, B. kasakhstanica (Rukavishnikova, 1956) and B. abayi (Klenina, 1984), in having a very narrow ventral muscle field with adductor scars elevated anteriorly on a high septum, a robust cardinal process almost completely occupying the narrow notothyrial cavity, and a weakly defined dorsal median fold and ventral sulcus (for discussion see Popov et al. 2000). Only Schizophorella formosa Xu, 1979, from the Koumenzi Formation (Katian) of China (Qinghai Province), shows similarity to the Kazakh shells in having a very narrow ventral muscle field, with the adductor scars raised anteriorly on a high septum, but the Kazakh shells are significantly smaller, have a less prominent ventral sulcus and dorsal median fold originating anteriorly to midlength, and a coarser radial ornament, with only up to 24 ribs against 34–38 in the Chinese species. Family Plectorthidae Schuchert, 1929 Genus Plectorthis Hall & Clarke, 1892 Type species. Orthis plicatella Hall, 1847, from the Trenton Group (Sandbian) of New York State, USA. Plectorthis cf. licta Popov & Cocks, 2006 (Fig. 21N–P, S, T) Material. Locality 8506 (Mid Katian): conjoined valve exterior, BC 58767, dorsal internal mould, BC 58769; Locality 266 (Mid Katian): two dorsal internal moulds, NMW 2001.38G.245 (Fig. 21O, P), 246; Locality 3136, ventral internal mould, NMW 2001.38G.247 (Fig. 21N), dorsal internal mould, NMW 2001.38G.248 (Fig. 21S, T). Remarks. In having a relatively large subquadrate shell for the genus and multicostellate ornament, a small, strongly impressed ventral muscle field and a shallow dorsal sulcus fading anteriorly to mid-valve length,

J————————————————————————————————————————— Figure 20. A–K, N–P, Bokotorthis minuta sp nov.; A, B, NMW 2001.38G.40, dorsal and lateral views of conjoined valves, Locality 7975; C, D, NMW 2001.38G.43, dorsal valve, dorsal and lateral views, Locality 7975; E, I, NMW 2001.38G.44, dorsal internal mould and latex cast of dorsal interior, Locality 7975; F–H, NMW 2001.38G.42, holotype, ventral internal mould, latex cast of ventral interior, oblique lateral view of interior, Locality 7975; J, N, BC 60290, latex cast of dorsal exterior and enlargement showing ornament, Locality 1560; K, O, P, BC 58833, internal mould of conjoined valves, latex cast of dorsal interior, ventral and dorsal views of internal mould, Locality 1560. L, M, R, Bokotorthis cf. plicadua (Xu, 1979), Locality 8506; L, BC 58772, ventral internal mould; M, BC 58770, ventral internal mould; R, BC 58871, ventral internal mould. Q, S–B0 , Bokotorthis abayi (Klenina, 1984); Q, U, NMW 2001.38G.386, ventral internal mould, latex cast of ventral interior showing enlarged muscle field, Locality 1830; S, X, Z, NMW 2001.38G.437, conjoined valves, ventral, dorsal and lateral views, Locality 2423; T, NMW 2001.38G.542, latex cast of dorsal interior, Locality 1830; V, NMW 2001.38G.543, dorsal internal mould, Locality 1830; W, Y, A0 , B0 , NMW 2001.38G.489, conjoined valves, lateral, ventral, anterior and dorsal views, Locality 2423. Scale bars 1 mm (A–I, K, N–P), 2 mm (J, L–M, Q–B0 ).

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734 L. E. Popov and L. R. M. Cocks

Late Ordovician brachiopods specimens from the Akdombak Formation show much similarity to Plectorthis licta Popov & Cocks, 2006, originally described from the Degeres Beds in the upper part of the Dulankara Formation of the Chu-Ili Terrane. All the specimens in our Chingiz collection are distorted in various degrees and therefore their species affiliation can only be considered provisional.

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Zhejiangorthis is not congeneric with Ashinaorthis. Phaceloorthis Percival, 1991 is another plectorthid with fascicostellate radial ornament, however Ashinaorthis can be distinguished from this genus in having a variably developed ventral (not dorsal) sulcus, uniplicate anterior commissure, significantly finer radial ornament and dorsal adductor muscle scars whose anterior pair is smaller than the posterior pair.

Genus Ashinaorthis gen. nov.

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Type species. Mimella recta Klenina, 1984 (see below). Diagnosis. Shell slightly dorsibiconvex to subequally biconvex with a variably developed uniplicate anterior commissure and finely fascicostellate radial ornament. Ventral valve with shallow sulcus anterior to mid-length. Ventral interarea apsacline with an open triangular delthyrium laterally defined by incipient delthyrial plates. Dorsal valve with orthocline interarea and shallow sulcus in the umbonal region reversed into a low median fold anterior to mid-length. Ventral interior with long, divergent dental plates and a strongly impressed, bilobed muscle field with narrow triangular diductor muscle scar raised anteriorly and slightly shorter than strongly impressed adductor muscle scars. Mantle canal system saccate with divergent vascula media. Dorsal interior with blade-like, anteriorly divergent brachiophores and a ridge-like cardinal process with a thickened shaft and a crenulated myophore, bisecting a low, subtriangular notothyrial platform. Dorsal median ridge low and short. Dorsal adductor muscle field gently impressed, quadripartite with a larger posterior pair of adductor scars. Remarks. Ashinaorthis differs from Zhejiangorthis Liang in Liu et al. 1983, from the Upper Ordovician of South China, which was reassigned to Mimella by Zhan & Cocks (1998), in having finely fascicostellate ornament, brachiophore bases converging with the base of the notothyrial platform, a weakly developed short dorsal median ridge and a larger anterior pair of dorsal adductor scars, all in contrast to the Chinese species. Further comparison is difficult because data on the dorsal valve morphology of Zhejiangorthis are still inadequate, but it is certain that

Ashinaorthis recta (Klenina, 1984) (Fig. 22A–H) 1984 Mimella brevis Rukavishnikova; Klenina: 45, pl. 1, fig. 9, pl. 3, figs 5, 8–13, pl. 4, figs 4, 5, 9–18. 1984 Mimella recta Klenina: 47, pl. 3, figs 14–16. Holotype. IGNA 411/46, conjoined valves, Locality 604 of Nikitin (1972), Taldyboi Formation (Katian), west side of Taldyboi River, Chingiz Range. Material. Locality 282 (Early Katian), one pair of conjoined valves, NMW 2001.38G.391, one dorsal internal mould, NMW 2001.38G.729; Locality 1830 (Early Katian), one external mould of conjoined valves, NMW 2001.38G.698 (Fig. 22G, H), one ventral external mould, NMW 2001.38G.699; Locality 1852 (Early Katian), one ventral internal mould, BC 60231 (L 13.8, W 18.6, Iw 18.0, Ml 5.8, Mw 5.2) (Fig. 22E); Locality 1858 (Early Katian), one internal mould of conjoined valves, NMW 2001.38G.408 (Fig. 22A, B), three ventral internal moulds, NMW 2001.38G.395 (Fig. 22C), 701–702, one ventral external mould, NMW 2001.38G.721; Locality 2133 (Early Katian), one dorsal internal mould, NMW 2001.38G.700 (Fig. 22F). Description. Shell slightly dorsibiconvex to subequally biconvex, transverse suboval, about 75% as long as wide, with maximum width at mid-length, and slightly more than half as thick as long. Hinge line about two-thirds valve width; cardinal extremities rounded. Anterior commissure variably uniplicate. Ventral valve evenly convex, with a broad shallow sulcus originating slightly posterior to the mid-valve and gradually deepening anteriorly.

J————————————————————————————————————————— Figure 21. A–I, Phragmorthis eximia sp. nov., Locality 7975; A, NMW 2001.38G.48, latex cast of ventral interior; B, NMW 2001.38G.55, ventral interarea; C, I, NMW 2001.38G.56, ventral valve lateral and ventral views; D, NMW 2001.38G.47, holotype, latex cast of dorsal interior; E, H, NMW 2001.38G.52, ventral exterior, dorsal and lateral views; F, NMW 2001.38G.71, latex cast of ventral interior; G, NMW 2001.38G.67, dorsal exterior. J–L, Phragmorthis sp.; J, BC 58764, dorsal internal mould, Locality 8506; K, BC 58765, ventral internal mould. Locality 8506; L, NMW 2001.38G.798, latex cast of dorsal interior, Locality 1834. M, Q, Phaceloorthis? sp., Locality 7975; M, NMW 2001.38G.39, dorsal internal mould; Q, NMW 2001.38G.38, exfoliated ventral exterior. N–P, S, T, Plectorthis cf. licta Popov & Cocks, 2006; N, NMW 2001.38G.247, ventral internal mould, Locality 3136; O, P, NMW 2001.38G.245, latex cast of dorsal interior and strongly distorted dorsal internal mould, Locality 266; S, T, NMW 2001.38G.248, latex cast of dorsal interior and dorsal internal mould, Locality 3136. R, U, Giraldiellid gen. et sp. indet.; R, BC 58808, ventral internal mould, Locality 2080; U, BC 58852a, ventral internal mould, Locality 2080. V–Y, Alpeis tolenensis (Borissiak, 1972), Locality 3088; V, W, BC 60226, enlarged cardinalia and latex cast of dorsal interior, Locality 3088; X, Y, NMW 2001.38G.704, ventral and posterior view of conjoined valves showing almost catacline ventral interarea and incipient deltidial plates. Scale bars 1 mm (A–K), 2 mm (L–Y).

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Late Ordovician brachiopods Ventral interarea moderately high, triangular, curved in the umbonal area. Delthyrium narrow, triangular with narrow deltidial plates on the lateral margins. Dorsal valve evenly convex with a planar, anacline interarea and a weak sinus originating at the umbo and fading completely towards mid-valve. Poorly defined dorsal median fold may be present in the anterior half of the shell. Radial ornament finely fascicostellate, with up to 16 rounded primary ribs in the ventral umbo and up to 14 costellae per 3 mm along the anterior margin of mature specimens. Ventral interior with strong teeth and thin divergent dental plates. Ventral muscle field subtriangular, bilobed, surrounded by strong muscle bounding ridges, slightly longer than wide and about 40% valve length. Ventral mantle canals saccate with divergent vascula media. Dorsal interior with ridge-like, anteriorly divergent brachiophores, with brachiophore bases convergent towards the bottom of the low, narrow subtriangular notothyrial platform. Cardinal process high, blade-like, with a thickened shaft and crenulated myophore. Dorsal median ridge short and low. Adductor muscle scars gently impressed, with a large posterior pair of scars. Remarks. The specimens described by Klenina from the Taldyboi Formation of the Chingiz Range as Mimella brevis Rukavishnikova, 1956 are not congeneric or conspecific with that species, as discussed by Popov et al. (2000) and Popov & Cocks (2006). The shells from the Shiyanbe Formation of the central part of the Eastern Qinling Region of China, described and illustrated by Xu (1997) as Mimella cf. recta Klenina, appear to be a different genus to Ashinaorthis recta. They differ in having coarser fascicostellate radial ornament, a wider notothyrial platform and a rectimarginate anterior commissure and they may be assignable to Phaceloorthis Percival, 1991. Mimella recta differs from Zhejiangorthis zhejiangensis (Liang in Liu et al. 1983) from the Upper Ordovician of South China, which was reassigned to Mimella by Zhan & Cocks (1998), in having finely fascicostellate ornament, brachiophore bases converging with the base of the notothyrial platform, a weakly developed short dorsal median ridge, and in the large posterior pair of dorsal adductor scars. Family Plectorthidae Schuchert & Cooper, 1931 Genus Phaceloorthis Percival, 1991

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Type species. Phaceloorthis decoris Percival, 1991, from the Quondong Limestone (Mid Katian) of New South Wales, Australia. Phaceloorthis? sp. (Fig. 21M, Q) Material. Locality 7975 (Katian): ventral valve, NMW 2001.38G.38 (Fig. 21Q); dorsal internal mould, NMW 2001.38G.39 (Fig. 21M). Remarks. An exfoliated ventral valve shows remnants of fascicostellate radial ornament and a dorsal internal mould exhibits a small strongly impressed quadripartite adductor muscle field, with anterior adductor scars larger than posterior ones. The shells show a distinct resemblance to Phaceloorthis recondita Popov, Nikitin & Cocks, 2000, from the Otar Member of the Dulankara Formation (Early Katian) in the Chu-Ili Terrane. However, the cardinalia are not well enough preserved in the single dorsal internal mould available from the Akdombak Formation, and thus knowledge of the true generic affiliation of the taxon requires further specimens. Family Phragmorthidae Williams, 1965a Genus Phragmorthis Cooper, 1956 Type species. Phragmorthis buttsi Cooper, 1956, from the Pratt Ferry Formation (Darriwilian) of Alabama, USA. Phragmorthis eximia sp. nov. (Fig. 21A–I) Derivation of name. Latin eximius, extraordinary. Holotype. NMW 2001.38G.47, dorsal internal mould (Ld 8.8, W 13.3, Iw 9.8, Sl 7.3, NPl 2.9 (Fig. 21D), from Locality 5975 in the Akdombak Formation (Mid Katian), left-hand side of the River Bakanas, east of the River Kyztyluzen. Material. Paratypes from Locality 7975, two ventral internal moulds, NMW 2001.38G.48 (Lv 12.9, W 11.0, Iw 10.1, Il 4.2) (Fig. 21A), NMW 2001.38G.71 (Lv 10.6, W 9.0, Iw 7.7, Il 4.1), two conjoined valves, NMW 2001.38G.49 (Lv>10.5, Ld 9.3, W 11.5, T 7.7), NMW 2001.38G.52 (Lv 10.5, Ld 8.2, W 11.0, Iw 10.3) (Fig. 21E, H), four ventral valves, NMW 2001.38G.50

J————————————————————————————————————————— Figure 22. A–H, Ashinaorthis recta (Klenina, 1984); A, B, NMW 2001.38G.408, latex cast of dorsal interior and dorsal internal mould, Locality 1858; C, NMW 2001.38G.395, latex cast of distorted ventral interior, Locality 1858; D, NMW 2001.38G.699, latex cast of incomplete dorsal exterior, Locality 1830; E, BC 60231, ventral internal mould, Locality 1852; F, NMW 2001.38G.700, latex cast of dorsal interior, Locality 2133; G, H, NMW 2001.38G.698, incomplete conjoined valves, ventral view and posterior view showing ventral interarea with incipient deltidial plates. I–R, T, Alpeis tolenensis (Borissiak, 1972); I, L, BC 60227, dorsal exterior and lateral views, Locality 3088; J, M, BC 58891, dorsal exterior and lateral views; Locality 3088; K, N, NMW.2001.38G.705, dorsal exterior and lateral views, Locality 3088; O, BC 58852, latex cast of ventral exterior, Locality 3088; P, T, NMW 2001.38G.706, latex cast of ventral interior and ventral internal mould; Q, BC 58880, ventral internal mould, Locality 1766; R, BC 58886, ventral internal mould, Locality 3088. S, Alpeis? sp.; Locality 3136, NMW 2001.38G.708, ventral internal mould. Scale bars 2 mm.

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(Lv 13.2, W 13.0, Iw 10.1, Il 4.8, T 4.5), NMW 2001.38G.53 (Lv 9.2, W 10.7), NMW 2001.38G.55 (Fig. 21B), 56 (Fig. 21C, I), 57–67, 71 (Fig. 21F), four dorsal valves, NMW 2001.38G.54, 67 (Fig. 21G), 68–70.

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Diagnosis. Shell robust, strongly ventribiconvex, about as long as wide, with shallow dorsal median sulcus and weakly uniplicate anterior commissure. Radial ornament evenly multicostellate with 6–7 ribs per mm. Ventral interior with robust teeth, a distinct apical plate and a muscle field on a pseudospondylium confined to the bottom of an almost tubular delthyrial cavity. Dorsal interior with strongly thickened triangular median septum and a strongly impressed adductor muscle field extending anteriorly well beyond mid-valve. Notothyrial platform narrow, undercut anteriorly and occupying almost one-third valve length. Description. Shell strongly ventribiconvex, subpentagonal in outline, almost as wide as long and about 70% as thick as long. Hinge line about 90% of maximum shell width at about mid-length. Cardinal extremities rounded; anterior commissure weakly unisulcate. Ventral valve strongly and evenly convex, about 35% as thick as long with high (up to 4.8 mm), triangular, strongly apsacline interarea, gently curved in the umbonal part. Beak pointed, extending well beyond the hinge line. Delthyrium open and narrow with almost parallel sides, covered in the umbo by a gently concave apical plate. Dorsal valve transverse semioval, about 75% as long as wide, with a shallow median sulcus originating at the umbo and fading anteriorly. Lateral profile of dorsal valve moderately convex, with maximum height slightly posterior to mid-length. Dorsal interarea moderately high, curved, strongly anacline. Radial ornament multicostellate, with 6–7 ribs per mm at the anterior margin of mature shells. Ventral interior with robust teeth supported by very short, strongly thickened dental plates. Muscle field on pseudospondylium confined to the bottom of the narrow, almost tubular delthyrial cavity. Shell floor strongly swollen anterior to the muscle field. Mantle canal system saccate with subparallel vascula media. Dorsal interior with a high, narrow notothyrial platform strongly inclined posteriorly and undercut anteriorly, occupying almost one-third shell length. Cardinal process faint, ridge-like, bisecting the entire notothyrial platform. Brachiophores strongly thickened; their bases merged with the notothyrial platform. Median septum robust, high, subtriangular with an evenly curved anterior margin, terminating at about 15% of valve length from the anterior margin. Dorsal adductor muscle field with smaller transverse posterior adductor scars and deeply impressed, elongate suboval anterior adductor scars extending anteriorly slightly beyond the median septum and completely enclosed by strong muscle bounding ridges.

Remarks. Phragmorthis eximia can be distinguished from other Late Ordovician species of the genus (Cooper 1956; Popov et al. 2002) in having more robust internal characters, including an apical plate, strongly thickened teeth, brachiophores and a dorsal median septum, a very long notothyrial platform occupying almost one-third of the valve length, and a dorsal adductor muscle field extending slightly anterior to the median septum. The apical plate covering the umbonal part of the delthyrium was previously unknown in the genus. Phragmorthis sp. (Fig. 21J–L) Material. Akdombak Formation, Locality 8506, ventral valve, BC 58765 (Fig. 21K), dorsal internal mould, BC 58764 (Fig. 21J); Taldyboi Formation, Locality 1834, dorsal internal mould, NMW 2001.38G.798 (Fig. 21L). Remarks. This form, unlike Phragmorthis eximia, has an almost procline ventral interarea, short ventral muscle field, a notothyrial platform occupying only 20% of valve length, and a narrow, blade-like dorsal median septum. It represents a separate taxon and is closely comparable to the specimens described by Popov & Cocks (2006) from the Dulankara Formation of the Chu-Ili Range, Kazakhstan as Phragmorthis sp. The two may be conspecific, but that cannot be resolved on the existing material, because the specimens from the Akdombak Formation are only internal moulds, whereas the material from the Dulankara Formation are only dorsal exteriors. Family Wangyuiidae Zhang, 1989 Subfamily Wangyuiinae Zhang, 1989 Remarks. As reviewed by Williams & Harper (2000), Wangyuiidae includes three genera which are rather homogeneous. Wangyuia Zhang, 1989, from the Wenlock of Arctic Canada, is small and coarsely ribbed with a high, procline ventral interarea. Bowanorthis Percival, 1991, from the Early Katian of Australia, is also small and comparable with Wangyuia, but it has a much larger, anacline interarea. Toxorthis Temple, 1968, from the Hirnantian of England, is also confamiliar with the first two, but the material is rather poor. However, the fourth genus, Sigmelasma Potter, 1990 from the Late Katian of California and Hirnantian of Estonia (Hints 2012), is somewhat different in having a relatively smaller interarea and a biconvex profile. The new genus Enbektenorthis described below is comparable to Sigmelasma, but has relatively smaller cardinalia and a much more pronounced ventral beak, but is clearly within the same subfamily as Sigmelasma. Genus Enbektenorthis gen. nov.

Late Ordovician brachiopods Type species. Enbektenorthis molesta sp. nov.

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Derivation of name. After the ruins of Enbekten near the type locality. Diagnosis. Shell slightly ventribiconvex with a hinge line shorter than maximum width and a weakly unisulcate to rectimarginate anterior commissure. Ventral valve subcarinate posteriorly. Ventral interarea curved, apasacline, with open delthyrium; dorsal interarea low, planar, anacline. Radial ornament multicostellate. Ventral interior with strong teeth supported by short dental plates and muscle field on the anterior part of the elevated pseudospondylium. Ventral mantle canals saccate, with slightly divergent proximal parts of vascula media. Dorsal interior with ridge-like cardinal process with a bilobed myophore on a short shaft. Brachiophores blade-like with short, almost parallel bases. Dorsal adductor muscle field gently impressed, quadripartite with large anterior pair of adductor muscle scars. No notothyrial platform and dorsal median ridge. Remarks. Enbektenorthis shows some similarity to Sigmelasma, and in particular to the type species S. pantherae Potter, 1990, from the Kangaroo Creek Formation (Sandbian) of the Klamath Mountains, California, in having multicostellate radial ornament, broad subtriangular, strongly elevated anteriorly ventral adductor scars and blade-like brachiophores, and in the complete absence of a notothyrial platform and a dorsal median septum. The cardinal process in S. pantherae is inadequately known due to poor preservation; however, in the Kazakh shells it has a short shaft and bilobed myophore characteristic of some Wangyuiidae. Enbektenorthis molesta differs from S. pantherae in having much finer radial ornament, a strongly apsacline and gently curved ventral interarea, in the absence of fulcral ridges and the significantly larger (up to five times) size of the shell. It differs from other genera of the family in having an pseudospondylium elevated posteriorly; in addition it has multicostellate radial ornament, unlike Toxorthis Temple, 1968 and Wangyuia Zhang, 1989, a delthyrium without an apical plate, and a strongly apsacline ventral interarea, unlike Bowanorthis Percival, 1991, and a cardinal process with a bilobed myophore which is otherwise reported only in the Silurian genera of Wangyuiidae (Toxorthis and Wangyuia). Enbektenorthis molesta sp. nov. (Figs 16B0 , 23A–K) Derivation of name. Latin molestus, troublesome, disagreeable, annoying. Holotype. BC 58757 (Fig. 23C, H), dorsal internal mould (Ld 23.2, W 18.0, Iw 12.2), from the Akdombak Formation (Katian), upper reaches of River Bakanas, area between the rivers Tolen and Alpeis, Locality 8506.

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Paratypes. Locality 8506, ventral external moulds: BC 58751, BC 58752 (Lv 17.8, W 18.8) (Fig. 23A), BC 58753 (Lv 12.5, W 15.2) (Fig. 23B), ventral internal moulds, BC 58754 (Lv 14.2, W 14.2, Iw 13.2, 4.8, MVl 4.8) (Fig. 23D), BC 58755–56, BC 60291, dorsal external mould, BC 58761, dorsal internal moulds, BC 58757 (Ld 14.0, W 22.7, Iw 20.0) (Fig. 23C, H), BC 58758, BC 58759–60, BC58761, BC 58762 (Fig. 23E), BC 60467 ((Ld 9.9, W 15.2, Iw 11.0) (Fig. 23F, G); dorsal external moulds, BC 58763, BC 58768 (Fig. 23I–K); Locality 2088, two ventral external moulds, NMW 2001.38G.797.1–2; two ventral internal moulds, NMW 2001.38G.796 (Fig. 16B0 ), 793.3. Diagnosis. As for genus. Description. Shell slightly ventribiconvex, semioval, almost as long as wide to slightly transverse. Hinge line about 85% of shell width, which is posterior to midlength. Cardinal extremities obtusely rounded; anterior commissure weakly unisulcate to almost rectimarginate. Ventral valve subcarinate posteriorly to mid-length; lateral profile moderately convex, with maximum height of about one-third valve length. Ventral interarea gently curved, strongly apsacline, up to 4 mm high. Delthyrium open, narrow triangular. Dorsal valve slightly transverse with a shallow median sulcus originating in the umbonal area and gradually fading anteriorly. Lateral profile of dorsal valve gently convex, with maximum height about one-third length anteriorly from the umbo. Dorsal interarea low, planar, anacline. Radial ornament multicostellate, with 5 to 7 ribs per 3 mm at the anterior margin of mature shells. Ventral interior with strong teeth supported by short, divergent dental plates. Muscle field on pseudospondylium slightly excavated anteriorly, subpentagonal, completely enclosed by muscle bounding ridges occupying about one-third shell length, with a broad, subtriangular adductor scar which is strongly raised anteriorly, and strongly impressed narrow, strip-like diductor scars. Mantle canal system saccate with slightly divergent proximal parts of vascula media. Dorsal interior lacking notothyrial platform, with a cardinal process differentiated on a bilobed myophore and a short shaft. Brachiophores bladelike, with short, almost subparallel bases. Narrow, quadripartite adductor muscle field usually weakly impressed, bordered laterally by faint muscle bounding ridges, open anteriorly and with larger anterior adductor scars. No median ridge. Remarks. Similar and probably congeneric specimens were described by Xu (1997) as Howellites sp. from the Shiyanbe Formation of the central part of the Eastern Qinling Region of China, and they are also characterized by a relatively small, bilobed ventral muscle field, a narrow notothyrial cavity bounded laterally by subparallel brachiophore plates, and lack a notothyrial platform and

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median ridge. Further comparison with the Chinese specimens is difficult because of their inadequate preservation.

Alpeis tolenensis (Borissiak, 1972) (Figs 21V–Y, 22I–R, T)

Subfamily Alpeisinae subfam. nov.

1955 Doleroides sp.; Borissiak: 32, pl. 1, figs 5–10. 1972a Mimella tolenensis Borissiak: 174, pl. 47, figs 1–3. 1984 Hirnantia tolenensis (Borissiak); Klenina: 50, pl. 3, fig. 2, pl. 6, figs 11, 15, 17.

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Diagnosis. Dorsibiconvex Wangyuiidae with distinctive high, blade-like, curved brachiophores and widely divergent brachiophore bases almost parallel to the hinge line. Fulcral plates well developed. Remarks. Within Wangyuiidae, the new genus Alpeis described below differs from the others in several ways. It is dorsibiconvex, subcircular in outline with a narrow hinge line and has its maximum width at mid-length, much finer radial ornament and more equicostellate ornament, but most importantly it has distinctive curved brachiophores with widely divergent bases almost parallel to the hinge line unknown in other members of the family. Thus we are erecting a new subfamily for Alpeis. Genus Alpeis gen. nov. Type species. Mimella tolenensis Borissiak, 1972a, from the Akdombak Formation (Sandbian) of the Tolen River, Chingiz Range, Kazakhstan. Diagnosis. Shell dorsibiconvex with a straight, strongly shortened hinge line and gently uniplicate anterior commissure. Ventral interarea almost planar, strongly apsacline to catacline, with incipient deltidial plates; dorsal interarea curved, almost orthocline. Radial ornament multicostellate. Ventral interior with simple teeth and long dental plates almost enclosing a small, subtriangular muscle field with wider adductor scar strongly raised anteriorly. Ventral mantle canal system saccate with short vascula media branching at a short distance from the muscle field. Dorsal interior lacking distinct notothyrial platform. Cardinal process ridge-like with a bilobed posterior face. Brachiophores high, subtriangular with widely divergent bases almost parallel to the hinge line. Fulcral plates well developed. Adductor muscle field small, weakly impressed, bisected by a faint median ridge. Remarks. Alpeis is considered here as an aberrant member of the Family Wangyuiidae Zhang, 1989, because it has a triangular ventral muscle field with broad, strongly raised adductor scars, and lacks a notothyrial platform, but it differs from other genera of the family in having straight, widely divergent brachiophore bases, a narrow hinge line, strongly impressed mantle canals with vascula media bifurcating at a short distance from the muscle field, and an uniplicate (not unisulcate) anterior commissure. A steeply apsacline to catacline interarea and a bilobed cardinal process also occur occasionally in Wangyuiinae, but are not common features in that subfamily.

Holotype. CNIGR 1/9555, partly exfoliated conjoined valves, from the upper part of the Akdombak Formation (upper Katian) by the Tolen River, Chingiz Range. Klenina (1984, p. 50) mistakenly reported that the holotype came from the Ak-Chokka River in the Tarbagatai Range. Material. Locality 1756 (Late Katian), three dorsal valves, NMW.2001.38G.718–720; Locality 1766 (Late Katian), 13 pairs of conjoined valves, NMW.2001.38G.615–621, BC 58880 (Fig. 22Q), BC 58881–83, BC 58885, BC 58887, one ventral internal mould, NMW.2001.38G.614, one dorsal valve, BC 58884; Locality 3088 (Late Katian), a pair of conjoined valves, NMW.2001.38G.704 (Fig. 21X, Y), two ventral valves, BC 58897–98, two ventral internal moulds, BC 58886 (Fig. 22R), 706 (Fig. 22P, T), one ventral external mould, BC 58852 (Fig. 22O), 13 dorsal valves, BC 58889–90, BC58891 (Fig. 22J, M), BC 58892–95, BC 58899, BC 60226 (Fig. 21V, W), BC 60227 (Fig. 22I, L), BC 60228–30, BC 60232, NMW.2001.38G.705 (Fig. 22K, N), two dorsal internal moulds, NMW.2001.38G.703, 707. Description. Shell strongly dorsibiconvex, slightly transverse, suboval to almost circular in outline, about 70% as long as wide. Hinge line significantly shorter than maximum width at mid-length (80%); cardinal extremities broadly rounded. Anterior commissure slightly unipicate. Ventral valve profile moderately convex, with maximum height at one-third to one-quarter valve length. Ventral interarea moderately high, triangular, almost planar, strongly apsacline to almost catacline, with narrow triangular delthyrium with incipient deltidial plates on the margins. Weakly defined ventral sulcus developed anteriorly to mid-length. Dorsal valve lateral profile strongly convex, more strongly curved in the posterior half, with maximum height slightly posterior to the mid-length. Umbonal region strongly swollen, hanging slightly over the hinge line. Dorsal interarea curved, almost orthocline. Radial ornament finely multicostellate, with 6 to 8 ribs per 3 mm along the anterior margin of mature specimens. Ventral interior with strong teeth supported by long, divergent dental plates. Ventral muscle field small, subtriangular, strongly impressed, with anterior border between a quarter and one-third valve length mainly within the floor of the delthyrial cavity. Adductor scar subtriangular, raised anteriorly, slightly longer and wider than gently impressed

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diductor scars. Mantle canal system strongly impressed, saccate, with vascula arcuata branching from widely spaced vascula media at a short distance from the outer boundary of diductor scars. Dorsal interior with a narrow and deep notothyrial cavity occupied almost completely by a posteriorly bilobed cardinal process supported by a low, narrow shaft not differentiated from a faint median ridge bisecting weakly impressed adductor muscle field. Brachiophores triangular, blade-like, with widely divergent bases almost parallel to the hinge line. Sockets deep, transverse, subtriangular, with well-developed fulcral plates.

field with a subtriangular adductor scar about equal in length and width, and gently impressed diductor scars. The specimens resemble Giraldiella Bancroft, 1949, but cannot be confidently attributed to this genus.

Remarks. This species was originally assigned to Mimella by Borissiak (1972a), but later transferred to Hirnantia by Klenina (1984); however, the shell fabric in Alpeis tolenensis is undoubtedly impunctate and the cardinalia with widely divergent brachiophore bases have no analogies with the genera assigned to the Family Draboviidae, as revised by Williams & Harper (2000). Specimens from the Upper Ordovician of Mount Kara-Bushir described and illustrated by Borissiak (1955) as Doleroides sp. are closely similar and are considered here as conspecific with Alpeis tolenensis.

Dalmanella kotyrzhalica sp. nov. (Figs 23L–P, 24M, Q–W)

Alpeis? sp. (Fig. 22S) Material. Locality 3132 (Mid Katian), two ventral internal moulds, NMW 2001.38G.709, 731; Locality 3136 (Mid Katian), two ventral internal moulds, NMW 2001.38G.708 (Fig. 22S), 799. Remarks. The ventral internal moulds show some general similarity to Alpeis tolenensis, including a relatively small ventral muscle field, which is raised anteriorly; however, the mantle canals are weakly impressed and the ventral interarea is distinctly apsacline, unlike A. tolenensis. Without knowledge of the dorsal valve morphology, precise generic affiliation of the specimens cannot be made. Family Giraldiellidae Williams & Harper, 2000 Giraldiellidae gen. et sp. indet. (Fig. 21R, U) Material. Locality 43 (Hirnantian?): one ventral internal mould, BC 58808 (Fig. 21R); Locality 2080; one ventral internal mould, BC 58852a (Fig. 21U). Remarks. Two ventral internal moulds are characterized by transverse shells with hinge lines slightly shorter than maximum shell width, and low apsacline ventral interareas. Remnants of multicostellate ornament can be seen on the peripheral parts of the shell surface. The ventral interior has a relatively small subpentagonal ventral muscle

Superfamily Dalmanelloidea Schuchert, 1913 Family Dalmanellidae Schuchert, 1913 Genus Dalmanella Hall & Clarke, 1892 Type species. Orthis testudinaria Dalman, 1828, from the Dalmanitina Beds (Hirnantian) of V€asterg€ otland, Sweden.

Derivation of name. After the Kotyrzhal hills on the east side of the River Tolen in the type area. Holotype. NMW 2001.38G.794 (Ld 5.6, W 7.1, Iw 6.0, BBw 2.7, Ml 2.7, Mw 3.1 (Fig. 24Q), dorsal internal mould, from the Akdombak Formation (Katian), on the east side of the Zhanybek River, north of the Mount Akdambak, Locality 256. Paratypes. Locality 256 (Late Katian), one dorsal internal mould, NMW 2001.38G.762, one dorsal internal mould, NMW 2001.38G.782; Locality 45 (Late Katian): two ventral internal moulds, NMW 2001.38G.783–784, one dorsal external mould with attached ventral interarea, NMW 2001.38G.785, one dorsal internal mould, NMW 2001.38G.800; Locality 256 (Late Katian), a pair of conjoined valves, NMW 2001.38G.767, one ventral valve, NMW 2001.38G.768 (Fig. 23N–P), one ventral internal mould, NMW 2001.38G.763 (Fig. 24U), two dorsal external moulds with attached ventral interarea, NMW 2001.38G.765–766 (Lv 10.6, W 9.2, Iw 5.4, Ml 3.8, Mw 2.8, dorsal external mould, NMW 2001.38G.761, 764; Locality 2083 (Late Katian), one dorsal internal mould, BC 58734, one ventral external mould, BC 58730, one ventral internal mould, BC 58733, one dorsal external mould, BC 48732, one dorsal internal mould; Locality 2084 (Late Katian), four ventral external moulds, NMW 2001.38G.742–744, 748 (Fig. 24M), four dorsal external moulds and ventral interarea, NMW 2001.38G.738 (Ld 5.4, W 7.6, Iw 5.2) (Fig. 23M), 739 (Lv 8.0, Ld 7.2, W 9.0, Iw 6.4) (Fig. 23M), 740 (Ld 5.8, W 8.8, Iw 5.4) (Fig. 23M), 741, three dorsal external moulds, NMW 2001.38G.745–747; Locality 3126 (Late Katian), six ventral internal moulds, NMW 2001.38G.750–752, 756 (Fig. 24R, S), 758 (Lv 10.1, W 9.3, Iw 6.3, Ml 3.0, Ww 2.8), 759, two dorsal external moulds, NMW 2001.38G.748, 760, five dorsal internal moulds, BC 58847, NMW 2001.38G.753–755 (Ld 7.3, W 8.6, Iw 6.5, BBw 2.9, Ml 3.0, Mw 3.8) (Fig. 24T, W); Locality 85244, one internal mould of conjoined valves, NMW

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2001.38G.773, five ventral external moulds, NMW 2001.38G.770–771, 774, 780–781, one ventral internal mould, NMW 2001.38G.769, 772, three dorsal external moulds with attached ventral interarea, NMW 2001.38G.774–779.

muscle scars gently impressed, quadripartite, outlined by fine muscle bounding ridges, about 85% as long as wide and two-thirds valve length. Anterior adductor scars significantly larger than posterior ones. Dorsal median ridge vestigial to absent.

Diagnosis. Shell ventribiconvex with flattened dorsal valve, anterior commissure rectimarginate in mature specimens, radial ornament almost equally multicostellate with 7–8 ribs per mm. Dorsal valve with shallow umbonal sulcus rapidly fading anteriorly. Dorsal interior with narrow notothyrial platform. Cardinal process bilobed on a long ridge-like shaft terminated at the anterior end of the notothyrial platform. Dorsal median ridge commonly absent.

Remarks. Dalmanella kotyrzhalica is assigned to the genus as revised by Jin & Bergstr€om (2010) because it has a narrow, bilobate cardinal process, well-developed fulcral plates, multicostellate radial ornament, with a ventral median costa and a dorsal medial interspace, and endopunctae of two different sizes. Unlike most species of Dalmanella it has a cardinal process with a long shaft, terminating at the anterior margin of the notothyrial platform and lacks a dorsal median ridge. It differs from the type species Dalmanella testudinaria (Dalman, 1828), which was geographically widespread in the Hirnantian, in having a flattened dorsal valve, almost equally multicostellate radial ornament, cardinal process with a long shaft terminated at the anterior end of the notothyrial platform and an indistinct dorsal median ridge. The Kazakh specimens of D. testudinaria described and illustrated by Nikitin (in Apollonov et al. 1980) from the Zhalair Formation (Hirnantian) of the Chu Ili Range have no significant differences from the Baltoscandian representatives of the species in the character of their radial ornament (including ventral median rib and dorsal median interspace), endopunctation, dorsal cardinalia and adductor muscle field, and therefore their attribution to D. testudinaria is certain. The only other known Kazakh species of Dalmanella is D. cicatrica Nikitin in Apollonov et al., 1980, from the Zhalair Formation (Hirnantian) of the Chu-Ili Range, which is relatively small and has a less convex dorsal valve; however, D. kotyrzhalica can be distinguished from it in having an evenly convex ventral valve lacking a carina and umbonal cleft, a more strongly impressed ventral muscle field, a long shaft of the cardinal process bisecting the entire notothyrial platform, and in the absence of a dorsal median ridge.

Description. Shell ventribiconvex as long as wide to slightly transverse, suboval in outline about 80% as long as wide with maximum width at or slightly posterior to midlength. Hinge line about 85% as wide as maximum shell width; cardinal extremities broadly rounded. Anterior commissure weakly unisulcate in juveniles, rectimarginate in mature specimens. Ventral valve moderately and evenly convex in transverse and sagittal profile, with a strongly anacline, triangular interarea slightly curved dorsally. Delthyrium open, triangular. Dorsal valve very gently convex to almost planar with a low anacline interarea. Shallow sulcus originating in the umbonal area rapidly fading anteriorly. Radial ornament multicostellate, with a ventral median costa and a dorsal medial interspace, bounded by a pair of internally branched medial costellae and with 7– 8 ribs per 2 mm along the anterior margin of mature specimens. Concentric ornament with fine evenly spaced filae. Shell structure endopunctate with punctae of two different sizes; larger punctae in radial rows with two rows per rib. Ventral interior with strong, wedge-shaped teeth supported by divergent dental plates. Ventral muscle field, about 140% as long as wide and about two-thirds as long as the valve, bordered laterally and anteriorly by distinct muscle bounding ridges. Ventral adductor muscle scar slightly raised, slightly shorter and narrower than diductor muscle scars. Ventral mantle canals lemniscate with strongly impressed, long, subparallel vascula media. Dorsal interior with triangular, stubby brachiophores with strongly thickened bases, converging towards the narrow notothyrial platform. Fulcral ridges well defined. Cardinal process narrow, bilobate with a ridge-like shaft terminating at the anterior margin of the notothyrial platform. Dorsal adductor

Dalmanella sp. (Fig. 24I–L, N–P, X) Material. Locality 43 (Hirnantian?), one dorsal internal mould, BC 58809 (Fig. 24I, J); Locality 2080, external mould of a pair of conjoined valves, BC 60245 (Fig. 24P), four ventral external moulds, BC 58848–50, BC 60246b (Fig. 24K); ventral internal mould, BC 58849, three

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Figure 23. A–K, Enbektenorthis molesta sp. nov., Locality 8506; A, BC 58752, latex cast of ventral exterior; B, BC 58753, latex cast of ventral exterior; C, H, BC 58757, holotype, latex cast of interior, dorsal internal mould; D, BC 58754, ventral internal mould; E, BC 58762, dorsal internal mould; F, G, BC 60467, dorsal internal mould and latex cast of dorsal interior; I–K, BC 58768, latex cast of conjoined valves in posterior view, dorsal view of external mould and dorsal view of exterior, latex cast. L–P, Dalmanella kotyrzhalica sp. nov.; L, NMW 2001.38G.758, ventral internal mould, Locality 3126; M, NMW 2001.38G.738–740, dorsal view of two articulated shells and dorsal exterior, Locality 2084; N, O, NMW 2001.38G.768, lateral and ventral views of ventral valve, Locality 256; P, NMW 2001.38G.768, enlargement of exfoliated ventral exterior to show endopunctae, Locality 256. Scale bars 2 mm (A–O), 0.5 mm (P).

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ventral valves, BC 58689–90, BC 58698, two dorsal valves BC 58847 (Fig. 24X), BC 60269, dorsal internal mould BC 60246a; Locality 2081, two pairs of conjoined valves, BC 58688, BC 58857–58 (Fig. 24N, O), one dorsal external mould, BC 58688, dorsal valve; Locality 43, one dorsal internal mould, BC 58809; Locality 2081, BC 60241–42, BC 60244; Locality 2062, BC 60245 (Fig. 24P). Remarks. Dalmanella sp. is relatively common in the uppermost part of the Akdombak Formation, which is questionably assigned to the Hirnantian. It resembles Dalmanella kotyrzhalica in having a strongly ventribiconvex shell with a flattened dorsal valve and almost equally multicostellate radial ornament. It differs in having a weak but well-defined dorsal median sulcus, slightly coarser ribs (up to 6 per 2 mm), a shorter shaft in the cardinal process which does not reach the notothyrial platform margin, and a low and broad dorsal median ridge bisecting the adductor muscle field. Due to strong distortion, the shells cannot be named or allocated to a species. Family Dicoelosiidae Cloud, 1948 Genus Epitomyonia Wright, 1968 Type species. Epitomyonia glypha Wright, 1968, from the Boda Limestone (Late Katian), Dalarna, Sweden. Epitomyonia cf. glypha Wright, 1968 (Fig. 24A, B, F, G) 2006 Epitomyonia cf. glypha Wright; Nikitin et al.: 255, figs 21, 16, 17, 22. Material. Akdombak Formation, Locality 7975, conjoined valves, NMW 2001.38G.80 (Lv 5.5, W 7.1, T 2.8) (Fig. 24A), NMW 2001.38G.81 (Lv 6.2, W 7.2, T 2.8) (Fig. 24B, G). NMW 2001.38G.82, dorsal valve (Lv 5.2, W 7.0) (Fig. 24F). Remarks. In size, general external morphology, and characters of the radial ornament, these specimens are almost indistinguishable from those described by Nikitin et al. (2006) from the Angrensor Formation of north-eastern Central Kazakhstan as Epitomyonia cf. glypha, and

745

they are probably conspecific. Minor differences include a somewhat thicker (up to 50%) shell, and the absence of a strong median costa in the ventral sulcus. Epitomyonia sp. (Fig. 24C–E, H) Material. Locality 2080 (Hirnantian), ventral internal mould, BC 58810 (Fig. 24C, H); Locality 2081 (Hirnantian), two ventral internal moulds, NMW 2001.38G.709 (Fig. 24D); ventral external mould, BC 58851 (Fig. 24E). Remarks. Epitomyonia is rare in the Hirnantian worldwide, although it is relatively cosmopolitan in both the Katian and the Llandovery. These few specimens differ from Epitomyonia glypha Wright, 1968 in having a more pronounced ventral sulcus and coarser radial ornament, however there is not enough material to define the species. Order Pentamerida Schuchert & Cooper, 1931 Suborder Syntrophiidina Ulrich & Cooper, 1936 Superfamily Camerelloidea Hall & Clarke, 1894 Family Camerellidae Hall & Clarke, 1894 Genus Ilistrophina Popov, Cocks & Nikitin, 2002 Type species. Ilistrophina tesikensis Popov, Cocks & Nikitin, 2002, from the Anderken Formation (Late Sandbian) of the Chu-Ili Range, Kazakhstan. Ilistrophina? sp. (Fig. 25K) Material. Locality 79149, one ventral valve, NMW 2001.38G.397, and one dorsal valve, NMW 2001.38G.398. Remarks. Externally, specimens from the limestone in the Akdombak Formation show close similarity to topotypes of Ilistrophina keregetasica Nikitin, Popov & Bassett, 2006, from the Angrensor Formation of north-eastern Central Kazakhstan, in having a subpentagonal shell outline with maximum width anterior to mid-length, a small, not swollen dorsal beak, dorsal median fold and ventral median sulcus originating at mid-valve. However, they differ in their slightly stronger dorsal median fold, but the

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Figure 24. A, B, F, G, Epitomyonia cf. glypha Wright, 1968, Locality 7975; A, NMW 2001.38G.80, ventral valve exterior; B, G, NMW 2001.38G.81, ventral exterior, lateral view; F, NMW 2001.38G.82, dorsal valve exterior. C–E, H, Epitomyonia sp.; C, H, BC 58810, ventral internal mould, ventral and posterior views, Locality 2080; D, NMW 2001.38G.709, latex cast of ventral interior, Locality 2081; E, BC 58851, latex cast of incomplete ventral exterior, Locality 2081. I–L, N–P, X, Dalmanella sp.; I, J, BC 58809, latex cast of dorsal interior and dorsal internal mould, Locality 43; K, BC 60246b, latex cast of distorted ventral exterior, Locality 2080; L, BC 60246a, latex cast of distorted dorsal interior, Locality 2080; N, BC 58858, latex cast of dorsal exterior, Locality 2081; O, BC 58857, dorsal view of conjoined valves, latex cast, Locality 2081; P, BC 60245, dorsal view of conjoined valves, latex cast, Locality 2062; X, BC 58847, dorsal internal mould, Locality 2080. M, Q–W, Dalmanella kotyrzhalica sp. nov.; M, NMW 2001.38G.748, latex cast of ventral exterior, Locality 2084; Q, NMW 2001.38G.794, latex cast of dorsal interior, Locality 256; R, S, NMW 2001.38G.756, ventral internal mould and latex cast of interior, Locality 3126; T, W, NMW 2001.38G.755, latex cast of dorsal exterior and dorsal internal mould, Locality 3126; U, NMW 2001.38G.763, latex cast of ventral interior, Locality 256; V, NMW 2001.38G.762, latex cast of dorsal interior, Locality 256. Scale bars 2 mm.

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Late Ordovician brachiopods limited number of specimens and lack of dorsal interiors makes it impossible to confirm generic affiliation. Superfamily Pentameroidea M’Coy, 1844 Family Virgianidae Boucot & Amsden, 1963 Genus Holorhynchus Kiaer, 1902 Type species. Holorhynchus giganteus Kiaer, 1902, from the Holorhynchus Beds (Late Katian) of Sandvika, Oslo region, Norway.

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Holorhynchus giganteus latisulcifer Rukavishnikova & Sapelnikov, 1973 (Fig. 25A–J) 1955 Holorhynchus cf. giganteus Kiaer; Borissiak: 44, pl. 4, figs 1, 2. 1973 Holorhynchus giganteus latisulcifer Rukavishnikova & Sapelnikov: 90, pl. 1, figs 1–14, pl. 2, figs 9, 10. 1975 Holorhynchus giganteus giganteus Kiaer; Sapelnikov & Rukavishnikova: pl. 7, figs 1, 2. 1975 Holorhynchus giganteus latisulcifer Rukavishnikova & Sapelnikov: Sapelnikov & Rukavishnikova: 49, pl. 8, figs 1–14, pl. 9, figs 1–5. Holotype. IGNA 15/2010, ventral valve, Upper Ordovician, Katian, Holorhynchus giganteus Beds, Locality 96 of Kovalevskii in, 1970, area south of Shoptygak Lake, Chingiz Range, Kazakhstan. Material. Locality 1756, seven ventral valves, BC 58794 (Fig. 25I, J), BC 58797 (Fig. 25C, D), BC 58800–02, BC 58803 (Fig. 25A, B, E), BC 58877 (Fig. 25F), seven dorsal valves, BC 58795 (Fig. 25G, H), BC 58796, BC 58798–99. Remarks. Sapelnikov & Rukavishnikova (1975) assigned almost all the Holorhynchus shells from the Chingiz Terrane, with the exception of a few poorly preserved specimens from the upper Akdombak Formation (Sapelnikov & Rukavishnikova 1975, pl. 7, figs 1, 2), to Holorhynchus giganteus latisulcifer, which can be considered as a geographical variety of the distinctive early virgianid species that spread widely across low latitudes in the Late Katian (Rong et al. 2004). The somewhat smaller shell size, presence of a faint, but well-defined median

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groove bisecting the ventral valve, and the usual absence of incipient irregular plications, are amongst the characters used by Sapelnikov & Rukavishnikova (1975) to discriminate these shells from Holorhynchus giganteus giganteus Kiaer, 1902, which was originally described from Baltoscandia. However, Rong et al. (2004) pointed out that all those features vary considerably within individual populations of Holorhynchus giganteus and cannot be used for species-level classification. Order Rhynchonellida Kuhn, 1949 Superfamily Rhynchotrematoidea Schuchert, 1913 Family Rhynchotrematidae Schuchert, 1913 Subfamily Rostricellulinae Rozman, 1969 Genus Rostricellula Ulrich & Cooper, 1942 Type species. Rostricellula rostrata Ulrich & Cooper, 1942, from the Lebanon Formation (Sandbian), Tennessee, USA. Rostricellula sp. (Fig. 25L–R) 1984 Lepidocyclus laddi Wang; Klenina: 112, pl. 12, figs 2, 3, 7. Material. Locality N-511 (Late Katian): five conjoined valves, BC 60298–300, NMW 2001.38G.713 (Fig. 25Q, R), ventral valve, BC 60297 (Fig. 25O), ventral valve, NMW 2001.38G.710 (Fig. 25L, M); Locality 1756 (Late Katian), conjoined valves, NMW 2001.38G.711 (Fig. 25P), ventral valve, NMW 2001.38G.712 (Fig. 25N). Remarks. Rhynchonellide specimens from Locality 511 were originally identified by Klenina as Lepidocyclus laddi Wang, 1949, but the description was insufficient and there was no illustration of the cardinalia. Silicified shells from the same locality show a short dorsal median septum and a narrow cruralium without cardinal process. They can be confidently assigned to Rostricellula; however, more precise taxonomic affiliation is difficult due to the significant distortion of the specimens. Order Atrypida Rzhonsnitskaya, 1960 Suborder Atrypidina Rzhonsnitskaya, 1960

J————————————————————————————————————————— Figure 25. A–J, Holorhynchus giganteus latisulcifer Rukavishnikova & Sapelnikov, 1973, Locality 1756; A, B, E, BC 58803, interior, oblique lateral and exterior views of dorsal valve; C, D, BC 58797, ventral exterior, side view; F, BC 58877, incomplete ventral interior showing part of spondylium; G, H, BC 58795, dorsal posterior view, exterior; I, J, BC 58794, incomplete ventral interior, oblique posterior view of interior showing spondylium. K, Ilistrophina? sp., Locality 79149, NMW 2001.38G.398, dorsal exterior. L–R, Rostricellula sp.; L, M, NMW 2001.38G.710, dorsal interior, oblique anterior view of interior, Locality N-511; N, NMW 2001.38G.712, incomplete ventral exterior, Locality 1756; O, BC 60297, ventral interior showing incipient dental plates, Locality N-511; P, NMW 2001.38G.711, ventral view of conjoined valves, Locality 1756; Q, R, NMW 2001.38G.713, ventral and dorsal view of conjoined valves, Locality N511. S–W, Schachriomonia parva (Rukavishnikova, 1956); S–U, NMW 2001.38G.86, ventral dorsal and lateral views of internal mould of conjoined valves, Locality 7975; V, NMW 2001.38G.715, latex cast of dorsal exterior, Locality 1859; W, NMW 2001.38G.426, latex cast of ventral interior, Locality 2423. X, Y, Qilianotryma sp., NMW 2001.38G.87, anterior and dorsal view of strongly distorted shell, Locality 7975. Scale bars 1 mm (L–M, P), 2 mm (A–K, O, Q–Y).

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748 L. E. Popov and L. R. M. Cocks

Late Ordovician brachiopods Superfamily Atrypoidea Gill, 1871 Family Atrypinidae McEwan, 1939 Subfamily Spirigerininae Rzhonsnitskaya, 1974 Genus Qilianotryma Xu, 1979 Type species. Qilianotryma mirabile Xu in Jin et al., 1979, from Late Katian beds in Qinghai, China. Qilianotryma sp. (Fig. 25X, Y) Material. Locality 7975: three pairs of conjoined valves, NMW 2001.38G.87–89.

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Remarks. All three specimens are strongly distorted and partly exfoliated. In size, characters of radial ornament, ventral sulcus and dorsal median fold they closely resemble Qilianotryma suspectum (Popov in Nikiforova et al., 1982).

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(Early Katian), 23 specimens, including BC 60302–10; Locality 1835 (Early Katian), one ventral valve, NMW 2001.38G.725; Locality 3115 (Early Katian), ventral internal mould, BC 58813, NMW 2001.38G.230, one dorsal internal mould, NMW 2001.38G.228; Locality 282, two pairs of conjoined valves, NMW 2001.38G.388–389, one dorsal valve NMW 2001.38G.390. Locality 1830, BC 59306–17; Locality 1859 (Mid Katian), one ventral valve, NMW 2001.38G.392, one ventral external mould, NMW 2001.38G.393, one dorsal external mould, NMW 2001.38G.715 (Fig. 25V); Locality 2423, a pair of conjoined valves NMW 2001.38G.397, two ventral valves, NMW 2001.38G.527, 737, one ventral internal mould, NMW 2001.38G.426) (Fig. 25W), one dorsal external mould, NMW 2001.38G.727.

Type species. Schachriomonia schachriomonica Nikiforova, 1978, from the Archalyk Member of the Shakhriomon Formation (Katian) at Shakhriomon, Uzbekistan.

Remarks. A revised description and discussion of Schachriomonia parva was given by Popov et al. (1999). The species is relatively common in the Taldyboi Formation and the lower part of the Akdombak Formation. As was discussed by Popov et al. (1999), shells of Zygospira (Kuzgunia) bakanasensis (Klenina, 1984) fall well within the range of morphological variations observed for S. parva and the two are considered conspecific.

Schachriomonia parva (Rukavishnikova, 1956) (Figs 19M, 25S–W)

Subfamily Clintonellinae Poulsen, 1943 Genus Rongatrypa gen. nov.

1956 Zygospira parva Rukavishnikova: 162, pl. 5, figs 14–16. 1984 Zygospira (Kuzgunia) parva Rukavishnikova; Klenina: 114, pl. 11, figs 6–12. 1984 Zygospira (Kuzgunia) bakanasensis; Klenina: 116, pl. 11, figs 5, 15. 1999 Schachriomonia parva (Rukavishnikova); Popov et al.: 635, pl. 2, figs 1–9, text-figs 5, 6. 2006 Schachriomonia parva (Rukavishnikova); Popov & Cocks: 280, text-fig. 6I, K.

Derivation of name. After Rong Jia-yu, in appreciation of his invaluable contributions to Palaeozoic brachiopod studies.

Genus Schachriomonia Nikiforova, 1978

Type specimens. Holotype of S. parva, IGNA 64/1369, conjoined valves from the Akkol Member, Dulankara Formation (Katian), Chu-Ili Range, Kazakhstan. Holotype of S. bakanensis, IGNA 411/198, conjoined valves from the Akdombak Formation, Locality 800 of Klenina (1984). Material. Locality 70 (Early Katian), one ventral external mould, NMW 2001.38G.384 (Fig. 19M); Locality 72

Type species. Nalivkinia (Pronalivkinia) zvontsovi Nikitin, Popov & Bassett, 2003, from the Tauken Formation (Katian) of the Selety River basin, Kazakhstan. Diagnosis. Shell variably dorsibiconvex with uniplicate anterior commissure and a well-defined ventral sulcus and U-shaped dorsal median fold originating between the umbo and mid-length. Ventral valve with small, erect, pointed beak and an open triangular delthyrium. Radial ornament of simple rounded ribs. Concentric ornament of fine densely spaced filae. Growth interruptions weakly developed to almost absent. Ventral interior with small teeth supported by thin dental plates. Floor of the delthyrial cavity completely occupied by pedicle callist. Ventral muscle field large, extending anteriorly to the mid-valve.

J————————————————————————————————————————— Figure 26. A–G, Rongatrypa instabilis (Klenina, 1984), Locality 3142; A, NMW 2001.38G.320, latex cast of ventral interior; B, NMW 2001.38G.321, latex cast of ventral exterior; C, NMW 2001.38G.322, latex cast of dorsal interior; D, NMW 2001.38G.323, dorsal view of conjoined valves, latex cast; E, NMW 2001.38G.326, dorsal internal mould; F, NMW 2001.38G.325, ventral internal mould; G, NMW 2001.38G.327, latex cast of dorsal interior; H–L, Rongatrypa sp., Locality N-511; H, I, NMW 2001.38G.716, lateral and ventral views of ventral valve; J–L, NMW 2001.38G.717, ventral, dorsal and lateral views of distorted shell. M–Z, Pusillaguta gibbera Misius, 1986, Locality 70; M, NMW 2001.38G.622, dorsal exterior; N–P, NMW 2001.38G.624, dorsal, ventral and anterior views of conjoined valves; Q–S, NMW 2001.38G.625, lateral, ventral and dorsal views of conjoined valves; T, U, NMW 2001.38G.628, ventral valve in ventral and lateral views; V, NMW 2001.38G.629, ventral internal mould; W, NMW 2001.38G.630, ventral internal mould; X, Y, NMW 2001.38G.691, dorsal and ventral views of conjoined valves; Z, NMW 2001.38G.633, dorsal internal mould. Scale bars 2 mm.

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Ventral adductor scars narrow, lanceolate, completely enclosed by larger diductor scars. Dorsal interior with a narrow cruralium supported by a high median septum and a simple ridge-like cardinal process. Crura divergent, anteriorly directed. Spiralial cones of up to nine whorls, with dorsomedially directed apices. Jugal processes short, disjunct, posteriorly placed.

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Species assigned. In addition to the type species, the genus includes: Rhynchotrema instabilis Klenina, 1984, from the Upper Ordovician (Katian) Taldyboi and Namas formations of the Chingiz Terrane (redescribed below); Rhynchotrema rudis Rukavishnikova, 1956, from the Upper Ordovician (Katian) Otar Member of the Dulankara Formation in the Chu-Ili Terrane (Popov et al. 2000); and Nalivkinia (Anabaria) xichuanensis Xu, 1997, from the Upper Ordovician (Katian) Shiyanbe and Liujiapo formations of the eastern Qinlin Region, South China. Remarks. Most of the Kazakh species referred to Rongatrypa were previously assigned to rhynchonellide genera. Xu (1997) was probably the first to recognize the atrypide nature of similar shells from South China. Later, Nikitin et al. (2003) also considered them as early representatives of the Family Clintonellinae and described spiralia with dorsomedially directed apices and rudimentary, posteriorly located jugal processes for Rongatrypa zvontsovi. The new genus is characterized by the shell lacking carination, concentric growth lamellae or frills and radially continuous, evenly spaced ribs typical of Clintonellinae, but unlike Silurian representatives of the family (Clintonella Hall in Hall & Clarke, 1993, Anabaria Lopushinskaya, 1965, and Nalivkinia Bublichenko, 1927). Rongatrypa has a well-developed pedicle callist occupying the posterior half of the delthyrial cavity floor, a cruralium supported by a well-defined median septum, and a simple, ridge-like cardinal process, which is rather atypical for early atrypides. The Llandovery Nalivkinia (Pronalivkinia) Rukavishnikova, 1977 was reassigned to Clintonella by Copper (in Kaesler 2002); however, the former is characterized by a strongly uniplicate anterior commissure and a U-shaped anterior median fold, which is not typical of Clintonella, and it may represent a separate taxon. Externally Nalivkinia (Pronalivkinia) somewhat resembles Rongatrypa, but lacks a cruralium supported by a well-defined dorsal median septum and a ridge-like cardinal process. Rongatrypa instabilis (Klenina, 1984) (Fig. 26A–G) 1984 Rhynchotrema instabilis; Klenina: 110, pl. 10, figs 10–12, pl. 12, fig. 1. Holotype. IGNA 411/193, conjoined valves, from the Namas Formation (Katian), Locality 720 of Klenina

(1984) from south-west of Kainar village, Chingiz Range, Kazakhstan. Material. Locality 1842 (Early Katian), 22 articulated shells, NMW 2001.38G.283–299, NMW 2001.38G.306– 310, six ventral valves, NMW 2001.38G.300–306, 13 dorsal valves, NMW 2001.38G.307–319; Locality 1858, 26 conjoined valves, NMW 2001.38G.582–607, ventral valve NMW 2001.38G.608; Locality 3142, one external mould of conjoined valves, NMW 2001.38G.323 (Fig. 26D), 20 ventral valves, NMW 2001.38G.320 (Fig. 26A), 321 (Fig. 26B), 325 (Fig. 26F), 328–336, 360–364, 375, 376, 377, 42 dorsal valves, NMW 2001.38G.322 (Fig. 26C), 324–326 (Fig. 26E), 327, 337– 359, 365–374, 378–380. Description. Shell slightly dorsibiconvex, subpentagonal in outline, almost as long as wide. Anterior commissure strongly uniplicate. Ventral valve lateral profile moderately convex, with maximum height slightly posterior to mid-length. Ventral beak strongly curved dorsally. Ventral median sulcus about three-fifths as wide as the valve, originating at mid-length, rapidly deepening anteriorly and terminating in a high, semioval tongue. Dorsal valve strongly and evenly convex, with high but weakly laterally defined median fold originating at mid-valve. Radial ornament with 39–49 simple rounded ribs separated by narrow interspaces with up to 10 ribs in the ventral sulcus and up to 11 ribs on the dorsal median fold. Concentric ornament of fine, evenly spaced filae. Ventral interior with strong teeth and short, divergent dental plates continuing as muscle bounding ridges laterally defining a strongly impressed, subtriangular ventral muscle field. Base of the delthyrial cavity occupied by a pedicle callist. Muscle field large, with the anterior border at mid-valve length, with a narrow, adductor scar completely enclosed by large, flabellate diductor scars. Mantle canals unknown. Dorsal interior with a disjunct hinge plate, a narrow cruralium on a high median septum slightly less than one-third as long as the valve and a simple, thin, ridge-like cardinal process. Remarks. Rongatrypa instabilis differs from the other Kazakh species R. rudis and R. zvontsovi in having a larger shell size, more ribs (usually exceeding 40 in number), and in the dorsomedial fold and ventral sulcus originating at mid-length. Rongatrypa sp. (Fig. 26H–L) Material. Locality N-511 (Late Katian): two pairs of conjoined valves (NMW 2001.38G.716, 717). Remarks. A few distorted specimens of Rongatrypa recovered from the Holorhynchus giganteus Beds in the upper part of the Akdombak Formation differ from R.

Late Ordovician brachiopods instabilis in having slightly more elongate shells and coarser radial ornament with only three ribs in the sulcus and four ribs on the dorsal median fold. They may represent a new species, but the available material is not sufficient for its formal description. Suborder Anazygidina Copper in Copper & Gourvennec, 1996 Superfamily Anazygoidea Davidson, 1883 Family Anazygidae Davidson, 1883 Subfamily Anazyginae Davidson, 1883 Genus Pusillagutta Misius, 1986

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Type species. Pusillaguta gibbera Misius, 1986, from the Tez Formation (Middle Katian) of Sary-Dzhaz River basin, north-eastern Kyrgyzstan. Remarks. Pusillagutta was considered by Copper (in Kaesler, 2002) to be a junior synonym of Zygospira but it differs in having a non-carinate ventral valve with a sulciplicate anterior commissure and a dorsomedial sulcus bisected by a fold formed by a pair of accentuated ribs. Unlike Zygospira, Pusillagutta has long, well-developed dental plates and an incipient ridge-like cardinal process. However, the characters of the brachial supports remain unknown in the genus and its affiliation to the Anazygidae is considered here as provisional. Pusillagutta is the only anazygid genus yet documented from the Kazakh terranes. Pusillagutta gibbera Misius, 1986 (Fig. 26M–Z) 1986 Pusillagutta gibbera Misius: 211, pl. 25, figs 1–7. Holotype. Institute of Geology, Kyrgyzstan, Bishkek, 1212/5, conjoined valves, from the Tez Formation (Katian), Muzbulak River, southern slopes of Terskei Alatau, Sarydzhaz River basin, Kyrgyzstan. Material. Katian: Locality 70 (Early Katian), nine articulated shells, NMW 2001.38G.624 (Lv 5.3, Ld 4.8, W 6.1, T 3.3, Sw 4.0) (Fig. 26N, O), 625 (Lv 3.5, Ld 2.9, W 3.5, T 1.9, Sw 3.1) (Fig. 26Q–S), 626 (Lv 5.1, Ld 4.3, W 4.8, T 3.2, Sw 3.4), 691 (Fig. 26, X, Y), 692–696, 32 ventral valves, NMW 2001.38G.627; 628 (Fig. 26T–U), 632, 634–662, three ventral internal moulds, NMW 2001.38G.629 (Fig. 26V), 630 (Fig. 26W), 631; dorsal valves, NMW 2001.38G.622 (Fig. 26M), 663–690; one dorsal internal mould NMW 2001.38G.633 (Fig. 26Z). Description. Shell ventribiconvex, rostrate, subpentagonal in outline, about 95% as long as wide, with maximum width slightly anterior to the hinge line. Anterior commissure slightly sulciplicate to unisulcate. Ventral valve strongly and evenly convex with an erect, pointed beak slightly inclined dorsally. Delthyrium open, narrow, triangular. Ventral median fold originating slightly posterior to

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mid-valve. Lateral slopes almost straight to slightly concave in transverse profile. Dorsal valve gently convex with maximum depth at about two-fifths valve length. Dorsal sulcus originating at the umbonal area, divided medially by a low fold formed by a pair of accentuated ribs anterior to mid-length. Radial ornament costate, with rounded ribs separated by slightly narrower interspaces, with 4–6 ribs in dorsal sulcus, 5–7 ribs on ventral median fold and 8–10 ribs on flanks. Ventral interior with delicate teeth and thin, long, divergent dental plates. Posterior half of the derlthyrial cavity floor occupied by the pedicle callist. Ventral muscle field weakly impressed. Dorsal interior with disjunct hinge plates and an incipient ridge-like cardinal process. Remarks. Pusilagutta was originally described from the Sarydzhaz River basin, east Kyrgyzstan, in an area that represents the eastern termination of the Karatau-Naryn Terrane. The shells from Chingiz are less variable than the topotypes but otherwise morphologically indistinguishable and they are considered here as conspecific.

Acknowledgements The material described here was chiefly collected by O. P. Kovalevskii, M. A. Borrisiak and I. F. Nikitin. This paper has only been possible through access to the field notes and maps made by these late and warmly remembered former colleagues. Further specimens were collected by I. M. Kolobova and L. E. P. Thanks go to the Natural History Museum, London for facilities; in particular, some of the photographs were taken there by Phil Crabb. L. E. P. acknowledges support from the National Museum of Wales. The paper has benefitted from the constructive comments of Lars Holmer (Uppsala University), Ian Percival (Geological Survey of New South Wales) and Enrique Villas (Zaragoza University).

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descriptions of the Brachiopoda. Geological Society of London, Memoir, 3, 1–267. Williams, A. 1963. The Caradocian brachiopod fauna of the Bala District, Merionethshire. Bulletin of the British Museum (Natural History), Geology, 8, 327–471. Williams, A. 1965a. Superfamily Orthacea. Pp. 307–328 in R. C. Moore (ed.) Treatise on Invertebrate Paleontology. Part H, Brachiopoda. Geological Society of America and University of Kansas Press, New York and Lawrence. Williams, A. 1965b. Suborder Strophomenidina. Pp. 362–412 in R. C. Moore (ed.) Treatise on Invertebrate Paleontology. Part H, Brachiopoda. Geological Society of America and University of Kansas Press, New York and Lawrence. Williams, A. 1974. Ordovician Brachiopoda from the Shelve District, Shropshire. Bulletin of the British Museum (Natural History), Geology, Supplement, 11, 1–163. Williams, A. & Harper, D. A. T. 2000. Orthida. Pp. 714–782 in R. L. Kaesler (ed.) Treatise on Invertebrate Paleontology, Vol. H (Brachiopoda) revised. Geological Society of America and Kansas University Press, Boulder and Lawrence. Winchell, N. H. & Schuchert, C. 1892. Preliminary descriptions of new Brachiopoda from the Trenton and Hudson River Groups of Minnesota. American Geologist, 9, 284– 294. Woodward, S. P. 1852. A manual of the Mollusca; or, a rudimentary treatise of recent and fossil shells. John Weale, London, xviþ1–486 pp. Wright, A. D. 1968. A new genus of dicoelosiid brachiopod from Dalarna. Archiv f€ ur Zoologi, 22, 127–138. Wright, A. D. & Jaanusson, V. 1993. New genera of Upper Ordovician triplesiid brachiopods from Sweden. Geologiska F€ oreningens i Stockholm F€ orhandlingar, 115, 93– 108. Xu H. 1979. Brachiopoda. Pp. 60–112 in Y. Wang, S. Jin, H. Ye, H. Xu & D. Sun (eds) Palaeontological atlas of north-western China. 1, Qinghai. Geological Publishing House, Beijing, 393 pp. [in Chinese]. Xu H. 1997. Late Ordovician brachiopods from the central part of eastern Qinling Region. Acta Palaeontologica Sinica, 35, 544–574. [in Chinese] Zeng, Q. 1987. Brachiopoda. Pp. 209–245 in X. Wang (ed.) Biostratigraphy of the Yangzste Gorge area 2, Early Palaeozoic Era. Geological Publishing House, Beijing. [in Chinese]. Zhan, R. & Cocks, L. R. M. 1998. Late Ordovician brachiopods from South China and their palaeogeographical significance. Special Papers in Palaeontology, 59, 1–63. Zhang N. 1989. Wenlockian (Silurian) brachiopods of the Cape Phillips Formation, Baillie Hamilton Island, Arctic Canada. Palaeontographica, A206, 46–97. Zonenshain, L. P., Kuzmin, M. I. & Natapov, L. M. 2000. Geology of the USSR: a plate-tectonic synthesis. American Geophysical Union Geodynamics Series, 21, 1–242. Zhou, Z. & Zhen, Y. (eds). 2009. Trilobite record of China. Beijing, Science Press, 402 pp.

Appendix: locality data The list of fossil localities below gives some of the significant brachiopods.

Taldyboi Formation Locality 282 [48 470 4200 N, 79 020 1800 E]. Collected by Kovalevski from the River Beisenba, 2.8 km east of the River Taldyboi, at approximately the same horizon as Locality 1830

(Unit TB7). Ashinaorthis recta, Bokotorthis abayi, Schachriomonia parva and Wrightiops nikitini. Locality 1830 [48 480 2600 N; 78 590 5800 E]. The same horizon as Locality 602 of Nikitin (1972, fig. 66). Collected by Kovalevskii from Unit TB7 on the west side of River Taldyboi. Wrightiops nikitini, Ashinaorthis recta, Bokotorthis abayi, Schachriomonia parva and Sowerbyella (S.) papiliuncula. Locality 1831 [48 480 2600 N; 78 590 5600 E]. Collected by Kovalevskii from Unit TB7 on the west side of River Taldyboi. Wrightiops nikitini, Bokotorthis abayi and Sowerbyella (S.) papiliuncula. Locality 1832 [48 480 1500 N; 78 590 4100 E]. Collected by Kovalevskii from Unit TB9 on the west side of River Taldyboi. Sowerbyella (S.) papiliuncula, Kassinella tchingisensis. Locality 1833 [48 480 1900 N; 78 590 3500 E]. Collected by Kovalevskii from Unit TB9 on the west side of River Taldyboi. Glossellinae indet., Kassinella tchingisensis. Locality 1834 [48 480 2400 N; 78 590 1700 E]. A single specimen of Phragmorthis sp. was collected by Kovalevskii from Unit TB11 on the west side of River Taldyboi. Locality 1835 [48 480 2300 N; 78 580 5700 E]. Collected by Kovalevskii from Unit TB14 on the west side of River Taldyboi, just above Locality 604 of Nikitin (1972, fig. 66). Acculina phyaliformis, Schachriomonia parva, and Sowerbyella (S.) papiliuncula. Locality 1836 [48 480 2200 N; 78 580 5400 E]. Collected by Kovalevskii from Unit TB14 on the west side of River Taldyboi. Mabella semiovalis and Monomerella? antiqua. Locality 1838 [48 480 1500 N; 78 580 5000 E]. Collected by Kovalevskii from Unit TB14 on the west side of River Taldyboi. Buminomena abayi. Locality 1841 [48 480 1200 N; 78 580 55.3200 E]. Collected by Kovalevskii from shell bed in the upper part of Unit TB14, on the west side of River Taldyboi. Mabella semiovalis and Paracraniops ellipticus. Locality 1842 [48 480 1000 N, 78 580 5500 E]. Collected by Kovalevskii on the west side of River Taldyboi from a shell bed in the uppermost part of the formation (Unit TB16). Ectenoglossa? magna and Rongatrypa instabilis. Locality 1843. Collected by Kovalevskii on the west side of River Taldyboi from the uppermost part of the formation (Unit TB16). Ectenoglossa? magna. Locality 1844 [48 480 1600 N; 78 580 4700 E]. Collected by Kovalevskii from a shell bed in uppermost part of Unit TB16 on the west side of River Taldyboi. Mabella semiovalis. Locality 1852 [48 460 2800 N, 78 540 5500 E]. Collected by Kovalevskii in the upper reaches of the River Taldyboi. Isolated locality of intercalated green and lilac siltstones overlying agglomerate tuff of the Namas Formation. Ashinaorthis recta. Probably the same horizon as Locality 448 of Nikitin (1960, p. 94, text-fig. 3) which contains abundant trilobites, including Amphilichas, Ampyx, Bulbaspis, Dulanaspis and Remopleurides. Locality 1858 [48 440 1800 N, 79 100 5400 E]. Probably the same locality as 3336 of Nikitin (1972, fig. 66). Collected by Kovalevskii on the east side of the River Namas from shell beds in calcareous argillites (Unit TB14 of Nikitin 1960, p. 91). Paracraniops ellipticus, Ashinaorthis recta, Bokotorthis abayi, Buminomena abayi, Mabella semiovalis, Strophomena (Tetraphalerella) namasensis, Sowerbyella (S.) papiliuncula and Rongatrypa instabilis. Locality 2423 [48 480 2000 N, 79 00 1500 E]. Collected by Kovalevskii on the east side of the River Taldyboi from the same horizon as Localities 1830 and 1831 (Unit TB7). Wrightiops nikitini, Ashinaorthis recta, Bokotorthis abayi, Schachriomonia parva and Sowerbyella (S.) papiliuncula.

Late Ordovician brachiopods

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Akdombak Formation Locality 43 [48 330 19.0000 N; 79 030 1900 E]. Collected by Popov on the right-hand side of the River Tolen from the same horizon as Locality 2080, corresponding to Unit 12 (Hirnantian). Kozlowskites botobaicus, Chonetoidea enbektenensis, Cliftonia sp., Dalmanella sp., Eostropheodonta sp., Leptaena (L.) enucleata. Locality 45 [48 320 200 N; 78 510 3900 E]. Collected by Popov from Unit 10 on the east side of the River Zhanybek, 2.3 km north-west of Mount Akdombak. Brachiopods include Dalmanella kotyrzhalica and Kassinella kasbalensis. Locality 256 [48 320 100 N; 78 510 3500 E; ¼ Locality 597 of Bandaletov et al. (1965, fig. 2) and 30, Nikitin (1972, fig. 24)]. Collected by Kovalevskii on the east side of the River Zhanybek from Unit 10. Brachiopods include Dalmanella kotyrzhalica and Kassinella kasbalensis. Locality N-511 [48 320 3400 N; 79 30 3700 E]. Collected by Nikitin from argillaceous limestone in the upper part of the formation, corresponding to Unit 9 exposed on the east side of the River Tolen (Nikitin 1972, text-fig. 24). Luhaia? bakanasensis, Holorhynchus giganteus latisulcifer, Rongatrypa sp. and Rostricellula sp. Locality 593 [approximate coordinates 48 300 4600 N;  0 00 78 59 08 E], probably the same as Locality 40 of Nikitin (1972, fig. 24; 1973, table 5) and the same horizon as Locality 7975. Collected by Kovalevskii from silty limestones on the western side of River Bakanas. Anoptambonites sp. and Dulankarella? sp. Locality 601 Collected by Kovalevskii; poorly localized in the area north of Akdombak Mountain, a bed of grey argillaceous limestone corresponding to Unit 6 of the Akdombak Section. Brachiopods include Sowerbyella akdombakensis. Locality 659a. Collected by Kovalevskii; poorly localized in the lower reaches of the River Alpeis. Brachiopods include Anoptambonites sp. 1. Locality 667 [48 320 2200 N; 79 040 4700 E]. This is the same unit as Locality 3115 (probably Unit 5). Sampled by Kovalevskii greyish green, calcareous siltstones in the area between the Tolen and Alpeis rivers. Christiania aff. proclivis. Locality 669 [48 320 2200 N; 79 10 3100 E]. A single specimen of Luhaia? bakanasensis was collected from this locality by M. A. Borissiak in 1957. The position of the locality was identified from an aerial photograph but is outside the measured section, making its stratigraphical position uncertain due to the complex tectonics. Locality 1756 [48 320 3400 N; 79 30 3700 E]. Collected by Kovalevskii on the east side of the River Tolen from Unit 9 and is the same horizon as Locality N-511. Luhaia? bakanasensis, Holorhynchus giganteus, Rostricellula sp. Locality 1766 [48 330 0400 N; 79 030 1200 E]. Collected by Kovalevskii on the west side of the River Tolen from greenish grey sandy siltstones in Unit 11. Alpeis tolenensis. Locality 1859 (¼ 353/1958 and 1653/1963) [48 310 4700 N; 78 520 4600 E]. Dark grey limestone (Unit 6) on the northern slope of Mount Akdombak near the road to Karaul. Collected by Kovalevskii (the same horizon as Locality 7967). Brachiopods include Sowerbyella (S.) akdombakensis and Schachriomonia parva. Locality 2062 [48 330 1900 N; 79 030 1900 E]. Collected by Kovalevskii, on the west side of the River Tolen, from greenish grey siltstones in Unit 12 (Hirnantian). There is a report of Persculptograptus persculptus from about 5 m above in the overlying unit, but it cannot be verified, and must be discounted. Fauna includes the trilobite Mucronaspis, and the brachiopods Kozlowskites botobaicus, Chonetoidea enbektenensis, Dalmanella sp., Eostropheodonta sp., Leptaena (L.) enucleata and Cliftonia sp.

757

Locality 2080. Collected by Kovalevskii, from the same horizon as Locality 2062 (Unit 12) on the west side of the River Tolen. The trilobite Mucronaspis, and the brachiopods Trematis aff. taljaardi, Kozlowskites botobaicus, Chonetoidea enbektenensis, Cliftonia sp., Craniops pristinus, Dalmanella sp., Eostropheodonta sp., Epitomyonia sp., Katastrophomena sp. and Leptaena (L.) enucleata. Locality 2081. Collected by Kovalevskii from the same horizon as Locality 2080, also Unit 12 (Hirnantian). Kozlowskites botobaicus, Chonetoidea enbektenensis, Cliftonia sp., Craniops pristinus, Eostropheodonta sp. and Leptaena (L.) enucleata. Locality 2083 [48 300 4100 N; 79 00 5900 E]. Collected by Kovalevskii from greenish grey siltstones in the upper part of the formation about 1150 m east of Bakanas River, corresponding to Unit 8. Diambonioidea koknaiensis, Foliomena folium and Kassinella kasbalensis. Locality 2084 [48 300 4400 N; 79 00 0200 E]. Sampled by Kolobova from greenish grey siltstones in the upper part of the formation on the southern side of the River Bakanas, also corresponding to Unit 8. Dalmanella kotyrzhalica. Locality 2088 [48 310 2800 N; 79 00 4800 E]. This is an isolated locality on the north side of the River Alpeis, about 250 m upstream from its mouth. A small brachiopod collection sampled by Kolobova includes Diambonioidea koknaiensis and Enbektenorthis molesta. Locality 2401 [48 320 4400 N; 79 30 3700 E]. Collected by Kovalevskii from the upper part of the formation (probably from Unit 9) about 500 m east of the River Tolen. Acculina phyaliformis. Locality 3086 [48 310 2800 N; 78 480 3600 E]. Collected by Kovalevskii from black argillites of Unit 10 on the southern side of the River Kasbala at about 3.2 km west of Akdombak Mountain. Kassinella kasbalensis. Locality 3088 [the same horizon as Locality 1766]. Collected by Kovalevskii on the eastern side of the River Tolen from greenish grey sandy siltstones in the upper part of Unit 11. Alpeis tolenensis and Mabella sp. Locality 3114 [poorly localized, approximately 48 320 N;  0 79 5 E]. Collected by Kovalevskii from greyish green siltstones exposed south-west of the height 967.9 m (Fig. 8) and probably represents the same horizon within Unit 5 as Locality 667. Brachiopods include Kassinella kasbalensis and Olgambonites? sp. Locality 3115 [48 320 3000 N; 79 50 5400 E]. Collected by Kovalevskii from greyish green, calcareous siltstones corresponding to Unit 5 in the area between the Tolen and Alpeis rivers. Platymena sp., Sowerbyella (S.) akdombakensis, Testaprica ajaguzensis and Schachriomonia parva. Locality 3131 [the same horizon as Locality 1766]. Collected by Kovalevskii on the right-hand side of the River Tolen from slightly calcareous greenish grey sandy siltstones in Unit 11. Alpeis tolenensis. Locality 3132 [48 310 1900 N; 79 30 3400 E]. Collected by Kovalevskii from the probable equivalent of Unit 5 of the Tolen section, on the northern side of the River Alpeis west of the ruins of Kosubai. Alpeis? sp., Bellimurina sp., Testaprica ajaguzensis. Stricklandistrophia? sp. collected by E. V. Poyarkova in 1964 from Locality 2773 on the northern side of the River Alpeis at about 3.6 km upstream from its mouth (Sapelnikov & Rukavishnikova 1975, pp. 98, 162) probably came from the same horizon. Locality 3136 [48 310 900 N; 79 30 1900 E]. Collected by Kovalevskii on the northern side of the River Alpeis west of the ruins of Kosubai from greyish green fine-grained sandstone (probably equivalent to Unit 5 in the Tolen section). Christiania

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aff. proclivis, Leangella (L.) aff. paletsae, Shlyginia sp. 2, Plectorthis cf. licta and Alpeis? sp. Locality 7963 [48 310 1700 N; 78 520 4300 E]. Collected by Popov from light-grey limestones within Unit 4 of the Akdombak Mountain area. Probably equivalent to Locality 595 of Bandaletov et al. (1965, text-fig. 2). Monomerella sp. Locality 7967 [48 310 3000 N; 78 520 4300 E]. Collected by Popov from dark grey, argillaceous limestones within Unit 6 of the Mount Akdombak area. Sowerbyella (S.) akdombakensis and Schachriomonia parva. Locality 7975 [48 300 4600 N; 78 590 0800 E]. Specimens collected by Popov from calcareous argillites and nodular argillaceous limestones within Unit 6. Bellimurina sp., Mabella sp., Shlyginia sp., Bokotorthis minuta, Phaceloorthis? sp., Phragmorthis eximia, Qilianotryma sp. and Schachriomonia parva. Locality 8506 [approximate geographical coordinates 48 320 4000 N; 79 040 3000 E] ( ¼ Localities 266 of Kovalevskii 1975 and 1093 Kovalevskii 1957). Collected by Kolobova from greenish grey siltstones in the middle part of the formation in the area between the Tolen and Alpeis rivers. The precise stratigraphical position of the locality is unknown, but it probably belongs to Unit 1 of the Tolen section. Christiania aff. proclivis, Holtedahlina aff. orientalis, Anoptambonites sp., Dulankarella? sp., Mabella sp., Shlyginia sp., Bokotorthis cf. plicadua, Enbektenorthis molesta, Phragmorthis sp. and Plectorthis cf. licta. Locality 79149 [48 310 3500 N; 78 540 1900 E]. Collected by Popov from dark-grey limestone within Unit 4; contains numerous unidentified gastropods and bivalves and a few Ilistrophina? sp. Locality 85244 [48 310 5400 N; 78 510 10.3200 E]. Collected by Popov from dark-grey argillites of Unit 10 near the River Kasbala. Dalmanella kotyrzhalica, Kassinella kasbalensis and some orthides.

Other fossil localities Brachiopod samples taken from isolated localities across the Chingiz Range have given important supplementary material for this study, and are as follows. Area of the Tentek grave [approximately 49 190 3000 N; 78 000 E]. The most western outcrops of the Taldyboi Formation are along the road between Kainar and Semei in the area of the Tentek grave (Fig. 3, Section 1). The Upper Ordovician sequence there was outlined by Nikitin (1960, pp. 96–97, textfig. 5). The exposed part of the Taldyboi Formation is more than 850 m thick, with two fossiliferous units in the upper part, but the faunal assemblage reported by Nikitin (1960) from the area remains undescribed. A single sample in our possession, collected by O. P. Kovalevskii and L. E. Popov in 1970 (Locality 72), contains a monospecific association with Schachriomonia parva which was derived from the same limestone horizon as Unit 8 of Nikitin (1960).

Ashchisu River [approximately 49 100 N; 78 90 3000 E]. Two localities (70 and 2133) are on the east side of River Ashchasu near the mouth of Egendybulak stream (Fig. 3, Section 2). They are probably from the same horizon in the upper part of the Taldyboi Formation as Locality 70 from the area of the Tentek grave. Ectenoglossa magna, Buminomena abayi, Bokotorthis abayi, Pusillaguta gibbera, Sowerbyella (S.) papiliuncula and Schachriomonia parva. Upper reaches of the Kensai River [approximately 48 380 3000 N; 79 200 3000 E]. A single isolated Locality 3142 in the area was sampled by Kovalevskii (Fig. 3, Section 5). The fossil horizon is a shell bed formed by the disarticulated valves of Rongatrypa instabilis in tuffaceous sandstone in the upper part of the Taldyboi Formation and probably corresponds to Unit 15 of Nikitin (1960, fig. 6). North side of Balkybek River [48 240 5100 N, 78 590 1100 E]. This isolated Locality 3126, about 2.4 km north of the River Balkybek (Fig. 3, Section 8) in greenish grey argillites in the upper part of the Akdombak Formation, was sampled by Kovalevskii. Dalmanella kotyrzhalica and Kassinella kasbalensis. Mount Kara-Bushir [approximately 48 160 4000 N;  79 500 2000 E]. The area is situated about 50 km north-west of the town of Ayaguz. Here the Akdombak Formation is exposed on the northern slope of Mount Kara-Bushir, about 2.8 km south-west from the road connecting Ajaguz and Karaul (Fig. 3, Section 9). A horizon in the upper part of the Akdombak Formation was collected by O. I. Nekrasova in 1948 (Borissiak 1955, p. 77, Localities 2019–2026) and revisited by M. A. Borissiak and O. P. Kovalevskii in 1957. Two samples from the latter collection have been used in our study: Locality 1053 contains abundant Sowerbyella (S.) intricata in greenish grey silty sandstone, and is probably the same as Locality 2019 of Nekrasova (Borissiak 1955, pp. 48, 77); Locality 1055 is about 100 m north-west of Locality 1053 and also contains S. (S.) intricata and Rongatrypa? sp. Borissiak’s collection in CNIGR Museum also contains Alpeis tolenensis and Testaprica ajaguzensis. The specimens of Monomerella sp. described by Borissiak (1955) were sampled by Nekrasova in the upper reaches of the River Sarybulak about 10 km east-south-east of Mount Kara-Bushir. Tarbagatai Range, Abaktiigen Stream [47 250 0300 N;  81 460 3000 E]. The Upper Ordovician brachiopod faunas of the Tarbagatai Range are outside the present study; however, some undistorted specimens of Bokotorthis minuta from the upper part of the Kulunbulak Formation (Catenipora libera Beds) in the upper reaches of the River Bazar were from Locality 1560, on the eastern side of the Abaktiigen stream, shown on Nikitin (1972, text-fig. 70) as Locality 783.

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