Inarticulate brachiopods around the Middle-Upper ...

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Jan 4, 2010 - overlying the typical Skagen Limestone, contain ... represents the upper part of the Skagen Lirne- stone, but the ..... Bornholm (Denmark).
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Inarticulate brachiopods around the Middle-Upper Ordovician boundary in Västergötland Lars E. Holmer Version of record first published: 04 Jan 2010.

To cite this article: Lars E. Holmer (1986): Inarticulate brachiopods around the Middle-Upper Ordovician boundary in Västergötland, Geologiska Föreningen i Stockholm Förhandlingar, 108:2, 97-126 To link to this article: http://dx.doi.org/10.1080/11035898609452633

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Inarticulate brachiopods around the Middle-Upper Ordovician boundary in Vastergotland

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LARS E.IIOLMER

Ifolmer, L. E., 19860701: Inarticulate brachiopods around the hfiddfe-Upper Ordovician boundary in .VSstergBtland. Geologkka Ffireningerrr i Srockholrii Fiirliandlingar, Vol. 10s. Pt. 2, pp. 97-126. Stockholm. ISSN 0016-786X. Inarticulate brachiopods are described from the Upper Viruan (hiiddle Ordovician) and Lower Harjuan (Upper Ordovician) limestones in Gullhogen quarry, Viistergotland, southern Sweden. Sixteen species of inarticulate brachiopods (seven named, six of which are new) are assigned to 14 genera (13 named, one of which is new). The lingulids are treated under open nomenclature. One new acrotretacean genus (Rhiriorrera) is described as are the acrotretacean species Hkirrgerella feniris, Coriotrera? orbicdarir, Veliseprirrn srricrrori, Rhirrorreta rriiiscularb, Toryrielasrria? currata and T.? plaria. The stratigraphy of the hiiddleUpper Ordovician boundary interval in Viistergotland is briefly discussed. 0 Bracliiopoda, lriarticrclata, Acrorreracea, riew genus, Rhinotreta, biosrrarigraphy, Middle-Upper Ordoriciari boundary, Grrllliiigeri quarry, Vas/ergorlarrd,Sweden. Lars E. Holriier, ~lruririrreof Palaeorrrology, Box 558, S-75122 Uppsala, Sweden; 8 h’overnber 1985, revbed 10 February 1966.

Middle and Upper Ordovician inarticulate brachiopods in Sweden have been described previously only cursorily and illustrated in a few papers, notably Angelin & Lindstrom (1880), IIadding (1913, 19156), Troedsson (1918), Henningsmoen (1918) and Bergstrom (1968n, 196Sb). Outside Sweden, these faunas are not well known; there are few detailed descriptions based on SEM investigations of material isolated from insoluble residues. This is unfortunate for our understanding of Ordovician marine benthic biotas, of which inarticulates were probably important components. Moreover, these brachiopods appear to have considerable. biostratigraphic potential. This paper is the first part of a more comprehensive study of the systematics and biostratigraphy of Middle and Upper Ordovician inarticulate brachiopods from Sweden. During the course of this study it became apparent that the Upper Viruan and Lower Harjuan beds contain assemblages that are quite different from those lower in the sequence. Etching and collecting from calcilutites (Bestorp Limestone, Slandrom Limestone, and Upper Viruan limestones of uncertain stratigraphic position here referred to as ‘unit A’) in Gullhogen quarry, northern Billingen (within the town of Skovde) in Viistergotland, yielded an unusual fauna consisting predominantly of inarticulate brachiopods. The associated fauna of microfossils including ‘mazuelloids’, sponges, radiolarians and phosphatic tubes of P l ~ ~ p h a t t t t d iwill u be described in a separate paper. However, the verti-

cal distributions of these are given herein (Fig. 2). Graptolites, conodonts, scolecodonts and chitinozoans were also found in abundance. The palaeoecology of small inarticulate brachiopods has been discussed by numerous workers (for summaries see Rowell & Krause 1973; Percival 1978; Williams & Lockley 1983; IIarper et al. 1984). Following the interpretation of Schuchert (1911), Ruedemann (1934) and Bulman (1964) it is common to regard all minute inarticulates (especially those occurring in biack shales) as originally planktic or epiplanktic. However, as noted by Jaanusson (1984) and Bassett (1984) these interpretations have never been substantiated by unequivocal evidence. The majority of the inarticulate brachiopods in the present investigation are interpreted as benthic organisms. Nevertheless, Popov et al. (1982, p. 103) suggested that the lingulide I’nfertrln had an entirely pelagic lifecycle. This suggestion was based on some peculiarities in its shell structure (cf. Fig. 4 0 ) and clearly merits further investigation.

Material and methods The use of the acetic acid technique in isolating phosphatic shells from limestones has long been in general practice (Bell 1916, 1918). Kecently, however, this method has been improved by Jeppsson et al. (1985). By using a mixture of ‘old’ and used acid in combination with ‘fresh’ 1 0 %

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1 mm, 1 mm0.063 mm) and both fractions were picked. No heavy liquid or any other method of concentrating the microfossils was used; the use of heavy liquids can cause a concentration of dorsal valves in the heavy fraction as the mostly deep and matrix-filled ventral valves will occur in the float. From each rock sample thin sections were made and the particle size (the content of skeletal sand) determined by point-counting (grainsolid) according to the method of Jaanusson (1952, 1972). In the SEM work, standard orientations were used with the ‘light’ corning from the upper left corner. However, all plane views were photographed at a slight tilt, as it reduces deep shadows.

Outline of Upper Viruan and Lower Harjuan stratigraphy and correlation The lithostratigraphic classification of the uppermost Viruan (Middle Ordovician) and Harjuan (Upper Ordovician) sequence in Sweden was summarized and revised by Jaanusson (1963, 1982) and Skoglund (1963). As noted by these authors, the stratigraphy of the boundary interval between the Viruan and Iiarjuan Series in Vastergotland is complicated and not yet understood in detail (Fig. 1). A considerable break of varying magnitude is developed at the boundary, and the adjacent lithostratigraphic units vary ,laterally not only in thickness but also in composition (Fig. 1). Recently a brief description of the Upper Viruan and Lower Harjuan sequence in Gullhogen quarry was compiled by Jaanusson (1982, pp. 176-179). The present paper deals with the fauna of the sequence between the Harjuan Jonstorp Formation (basal part correlative with the zone of Dicellograptics coniplanatirs; Skoglund 1963) and the Viruan Dalby Limestone (top within the zone of Diplograptics midtidens). This interval

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comprises, in descending order, the IIarjuan Fjacka Shale, Bestorp Limestone, Slandrom Limestone and the Skagen Limestone. Between the latter two formations a unit, with a distinct assemblage of microfossils, is present, the precise correlation of which is unclear (‘unit A’; Fig. 1, 2 ) . The correlation of the fkstorp Limestone is still uncertain (Skoglund 1963). In order to clarify the stratigraphy of the sequence investigated, four cores through the Viruan and Harjuan sequence of Mstergotland were reexamined; Stora Asbotorp (Jaanusson 1963; Skoglund 1963; Grahn 1981), Bestorp (Skoglund 1963) and Skultorp (Skoglund 1963): The Slandrom Limestone in the Fyllamosse core (Bruun 1982), Ostergotland, and in the Fjacka section (e.g., Jaanusson 1953), Dalarna, was also examined. A full account of these investigations will be given elsewhere. IIowever, it is evident that the.stratigraphy of the sequence must be reinterpreted to some degree. The following data (1-5) are essential for this reinterpretation (considered in ascending stratigraphic order). (1) The lowermost beds (‘unit A’; Fig. 2), overlying the typical Skagen Limestone, contain a distinctive assemblage of inarticulate brachiopods (Fig. 2). This unit was included in the Skagen Limestone both in Gullhiigen quarry (Jaanusson 1982) and in the Stora h b o t o r p core (38.30-?39.30 m; the question mark indicates that the exact position of the boundary is uncertain). A similar assemblage (including Veliseptittn strictittti, Rhitiotretn ntirscitlnris, and Hisingerelln sp. nov. a? in addition to mazuelloids) could be recognized in an aphanitic grey calcilutite (“Formation uncertain” in Skoglund 1963) in the Skultorp core (14.11-14.42 m). In this core the unit is overlain by mudstones and shales of the Mossen Formation (containing Dicratiogrnpt i 6 clittgani). In the Skultorp core, the lower boundary of this formation is marked by a distinct discontinuity surface. ‘Unit A’ apparently falls within the zone of D. clitigatii ( i s . of Viruan age), but its correlation presents difficulties. Its inarticulate fauna cannot be compared with that of the underlying Skagen Limestone, which is siliceous, as at its type locality at Kinnekulle, and does not dissolve in weak acid. In spite of extensive search for macrofossils, none could be found in the unit from the Gullhogen quarry. On the other hand, the assemblage does not resemble that from the Skagen Limestone in the Fjacka section, Dalarna (IIolmer, unpublished). Thus, for the stratigraphic interpretation of this unit there are two main possibilities of equal merit: (a) the unit

Ordovician iirarriciilate brachiopodc 99

represents the upper part of the Skagen Lirnestone, but the composition of the fauna of inarticulate brachiopods in Vastergotland and Dalarna differs, (b) the limestone forms a separate stratigraphic unit above the Skagen Limestone, perhaps comparable to the 1Mossen Formation, or originally deposited during the break at the base of the Mossen Formation as developed on Kinnekulle (Fig. 1). (2) The presence of the Mossen Formation in the uppermost Viruan of Gullhogen quarry was indicated by Johansson (iri Jaanusson 1982, p. 177), based on the occurrence of Tretnspis cerioides. The trilobite is now identified as a new species of the Tretuspis seticortiis group (A. Owen, pers. comm. 1986), indicating a IIarjuan age of this fossiliferous, grey calcareous mudstone (10-15 cm thick). This unit was not encountered during this study presumably due to rapid s atial variation (it is not present in the Stora sbotorp core, situated c. 1.5 km N of Gullhogen) and the fact that quarrying has proceeded past the section where the original observations were made. According to Johansson the top of the Tretmpis-bearing bed was encountered 1.85 m below the top of the Bestorp Limestone and below a thin bed of black shale. The boundary between the Viruan and IIarjuan is probably situated directly below this black shale (sample 21, Fig. 2), which contains Clittincogrnptits cf. brevis? and Leptograptits flnccidirs ttincer? (these and the following graptolites were kindly identified by S. H. Williams, St. Johns, Newfoundland). It is probable there is a hiatus at the Viruan-Harjuan boundary, but as the break is within argillaceous beds its level is not clearly defined in the lithology. Mannil (1966) regarded the Mossen Formation as a probable equivalent to the lower Slandrom Limestone, whereas Jaanusson (1973) took the evidence to indicate a correlation with the upper part of the Mold3 Limestone. It is evident that the detailed stratigraphic position of the Mossen Formation, and its equivalents, requires further study. However, the view of Miinnil is adopted tentatively in this work (Fig. 1). (3) The limestone previously referred to the lower part of the Bestorp Limestone in Gullhogen quarry (lower 0.8 m in Jaanusson 1982, p. 177) and the Stora Asbotorp core (37.55-38.30 m; Skoglund 1963; Grahn 1981) differs lithologically from the Bestorp Limestone (sensit stricto) in lack of lamination, higher content of skeletal sand (Fig. 2) and lighter colour. Despite intensive search for macrofossils none was encountered, except a find in the Stora Asbotorp core

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100 Lars E. Iloliner

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f i g . 2. Occurrence of inarticulate brachiopods and other microfossils in the Upper Viruan and Lower Ilarjuan sequence of Gullhogen quarry. Squares refer to specimens in the insoluble residue, which were identified unconditionally. A question mark indicates that the identification is conditional (cf.). Dots refer to occurrences in black shales, and a dot tvith a star occurrences in thin sections. J. = Jonstorp Formation, F. = Fjicka Shale.

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GFF 106 (1966)

(38.00 m) of Pririinspis bestorperisis Bruton, previously only known from the upper part of the Bestorp Limestone at the type locality (Bruton 1967). The assemblage of meiofauna differs conspicuously from that in the overlying limestone but shows similarities with ‘unit A’ (Fig. 2). A soniewhat similar assemblage (including Hisirigerella sp., Conotreta? orbiciilnris, and mazuelloids) occurs in the Skultorp core (13.75-13.80 m) and on either side of the Skagen-Bestorp boundary in the Bestorp core (assemblage including Pateriila sp., IIisirigerelln s ~ . Conotretn? , orbiciilaris, Toryrielnsriin? plnrin, and mazuelloids). A hint as to the correlation of this unit is provided by the occurrence of a somewhat similar assemblage of rneiofauna (consisting of, e.g., Iiisirigerella sp. nov. a, Rliiriotretn sp., Conotreta? orbiciilaris, Pnteriila sp., and mazuelloids) in the . Fyllamosse core (50.70-54.50 m), Ostergotland, in beds referred to the Slandrom Limestone (Bruun 1982, p. 96). Previously, equivalents of the Slandrom Limestone were assumed to be missing in Viistergotland, that is, they were included in the hiatus at the base of the Harjuan Series (Jaanusson 1963; Skoglund 1963), or were considered to be represented partly by the Bestorp Limestone (Miinnil 1966). The data referred to briefly above now suggest that in many sections in Vastergotland the Bestorp Limestone, as previously defined, is a composite unit possibly including an equivalent to part of the upper Slandrom Limestone. This is supported by the occurrence of a meiofaunal assemblage (e.g., Rliiriotretn nuiisciilaris, ToryrueIasriin? ciirvnta?, Conotreta? orbiciilaris?, and mazuelloids) in the upper Slandrom Limestone of the Fjicka section, Dalarna (Jaanusson & Martna 1938). This fauna, which needs a more detailed study, is somewhat similar to that of GullhBgen quarry, and the lower portion of the Bestorp Limestone is therefore referred tentatively to the Slandroni Limestone. (4) Only the upper one metre of the Bestorp Limestone as defined by Jaanusson (1982) in Gullhogen quarry and by Skoglund (1963) and Grahn (1981) in the Stora Asbotorp core (36.5037.55 m) is comparable lithologically and faunistically with the Bestorp Limestone (serisii stricto) at its type locality (Skoglund 1963). It consists of carbonate-rich, dense, dark and laminated calcilutites, with a very low content of skeletal sand (Fig. 3) and a distinct assemblage of microfossils (Fig. 2). (5) A thin (0-10 cm thick) wedge of the F j k k a Shale is present locally on top of the Bestorp

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Limestone (F., Fig. 2). Graptolites collected from this unit, irz sitii and from loose material, include Dicellogrflptiu piiiiiiliis, Cliriincogrnptils cf. brevis, Orthograptuis nniplexicaiilis - an assemblage suggesting the Pleiirogrnptris Iirienris Zone (S. H. Williams, pers. comm. 1984). The same unit was previously known from the Stora Asbotorp core (Skoglund 1963). The above stratigraphic outline demonstrates that inarticulate brachiopods are useful biostratigraphic tools. In the limestones examined in this study, inarticulates represent almost the only group of fossils which can be evaluated biostratigraphically. There are practically no macrofossils, and the sequence from the base of the Skagen Limestone to the upper part of the F j k k a Shale is within the range of a single conodont zone (zone of Aiiiorpliogiiotliils siiperbics; Bergstrom 1971).

Distribution of microfossils Inarticulate brachiopods fall mostly into the size range of meiofauna (0.2-2 mm), except for the juvenile shells which are usually somewhat smaller. The distribution of inarticulates in the sequence was found to agree well with the three lithological units distinguished (Fig. 2). in the lowermost unit (‘unit A’, Fig. 3) the relatively coarser limestones (content of skeletal sand 815 %) yielded 13 species, represented by a total of 638 specimens (427 dorsal valves, 205 ventral valves, and 13 complete shells). On average (samples 11-13), 40 % are Rliiriotretn iiuiiscihris, 30 % are Veliseptiirii strictiini, and 20 % Toryrielasma? plana. In the middle unit (Slandrom Limestone, Fig. 3) the rocks are somewhat less coarse (5-9 % skeletal sand) and yielded six species represented by 295 specimens (148 dorsal valves, 147 ventral valves). On average (samples 14-16) 40 % are Hisirigerella sp. indet., 40 % are Pnteriila spp., and 10 % are Toryrielnsnia? ciirvata. In the upper unit (Bestorp Limestone) the extremely fine-grained and laminated rocks (less than 1 % skeletal sand) yielded five species represented by a total of 275 specimens (134 dorsal valves, 127 ventral valves, and 14 complete shells). On average (samples 17-19), Ihiirigerella teriiiis constitutes 98 %. No far-reaching conclusions can be drawn from the distribution of inarticulate brachiopods in a single section and a detailed discussion of inarticulate palaeoecology is not attempted. It is apparent, however, that the particle size of the

102 Lars E. Holrner

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Fig. 3. To the left particle size (contents of skeletal sand grains defined as grain-solid, according to method of Jaanusson 1952, 1972). Second column shows the absolute frequency of inarticulate brachiopod valves per 100 g limestone. The remaining columns give the relative frequencies of valves of those inarticulate species which form at least 10% of the total inarticulate brachiopod fauna in at least one sample. 'Others' include all taxa which constitute less than 10 % in all samples.

limestones in the sequence correlates in some way with the faunal distribution. Jaanusson (1984) discussed such changes in macrofaunal associations along gradients from graptolitic shales to coarser grained rocks. The fauna of the upper unit in the sequence (Bestorp Limestone, Fig. 2) is very similar to the fauna found in the Fjscka Shale. Possibly the Bestorp Limestone at this and other localities represents a lateral facies of the wide-spread graptolitic Fjacka Shale, as suggested by Skoglund (1963). More research (including close stratigraphic sampling and large samples) is required for a better understanding of the distribution and palaeoecology of inarticulates. At present it seems most reasonable to assume that the adult inarticulates, discussed herein, were benthic organisms (with the possible exception of Paferiila as discussed above). The adult inarticulates could have lived attached to skeletal grains on the soft bottom (cf., e.g., Curry 1983; Harper et al. 1984)

or to some firm-bodied animal or plant not preserved (see, e.g., Bassett 1984 for a review) or within the sediment (lingulaceans). Bassett (1984, p. 244) also suggested that some elongateconical acrotretids (torynelasmatines) might have had an interstitial life habit comparable to that of the Recent articulate Givyriia cupxzda. Because of the fine-grained nature of the limestones (where the individual pores of the original sediment must have been very small), such a life habit is highly unlikely for the torynelasmatines in this study. Sponge spiculae are found distributed throughout the sequence, especially in the black shale units (Fig. 2). It is therefore equally possible to picture inarticulates attached to living or dead sponges, much in the way of the paterinid Dictyotiiria from the Burgess Shale of British Columbia, which is found attached to colonies of the sponge Firariia (Whittington iti Conway Morr i s et al. 1982, p. 25, pl. R.).

GFF I08 (19S6)

Ordoviciaii iiinrricirlare brachiopods

the original material is mounted on slides with numbers (SMNH)Br 132333-132370.

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Systematic palaeontology The classification and terminology of the inarticulate brnchiopods used here mainly follo\vs that of Rowell (1965). Willianis 6: Rowell (1965), Biernat (1973), Krause 6: Rowell (1975) and Havlitek (1982). The term ‘shell’ is used for conjoined valves, otherwise, ‘dorsal’ and ‘ventral’ is used. Popov et al. (1982) noted that the term ‘protegulum’ of present usage niight not be correct, and suggested, following Biernat 6: Williams (1970), !hat the typical pitting on the apical part of acrotretids is the negative replica of a vesicular and organic shell. I Iowever, Stricker 6: Reed (1985) illustrated primary pitting on the outer surface of the protegulum of the Recent articulate Terebrtlfalinfrtltisverstl. No similar ultrastructural study on the protegulum of Recent inarticulates has been published. The established usage of ‘protegulum’ and ‘protegular stage’ is retained herein pending further studies and a better substitute terminology. The term ‘brephic’ growth stage is used setixii Williams 6: Rowell (1965) for the very first postlarval stage (with growth lines). Chuang (1971,1977) discriminated (embryonic) ‘protegula’ from the (planktie) ‘larval shell’ in some inarticulates. All illustrated material is from a single section in Gullhogen quarry (Fig. 2). However, additional Swedish occurrences of some selected taxa are listed under ‘distribution’. The exact geographic locations of sections and cores are given in: Skoglund (1963; Bestorp core and Skultorp core), Grahn (1981; Stora Asbotorp core), Bruun & Dahlman (1980; Fyllamosse core close to Vadstena (Granby structure), PI. l), Jaanusson 6: Martna (1918; Fjacka section, sample levels in Laufeld 1967). Og. = Ostergotland, Vg. = Vastergotland, Dal. = Dalarna. A question mark indicates that the identification from that area is conditional. Measurements (in millimetres) of the specimens have been made as follows: W = maximum width, L = sagittal length, H = maximum height of ventral valve, WI = maximum width of dorsal pseudointerarea, LI = maximum length of dorsal pseudointerarea, WM = maximum combined width of muscle scars, LM = maximum length of muscle scar, WP = maximum width of dorsal protegulum, LP = maximum length of dorsal protegulum. The mean E, m, and number (n) of measurements are given. All specimens are deposited in Naturhistoriska Riksmuseet (Swedish Museum of Natural History, SMNH), Stockholm. Only figured specimens are given individual numbers. The remainder of

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Superfamily LINGULACEA Menke, 1828 Sysfetnaficposition. - Phylum Brachiopoda Cuvier, 1805; Class Inarticulata Huxley, 1869; Order Lingulida Waagen, 1855. Diqtiosis. - See Rowell (1965, p. H262). Diwssioti. - Detailed systematic treatment of the lingulaceans collected during this study is outside the scope of the present paper, since the work would require much larger sample sizes. Thus the faunal list is not complete for this group (some unidentifiable large lingulids from the black shale units have been excluded). However, a few of the more common and interesting forms are discussed briefly under open nomenclature and some new ultrastructural features of the shells are illustrated.

Lirigrrlelln SaIter, 1866 Sysreriinric posirion. - Family Obolidae King, 1846; Subfamily Lingulellinae Schuchert, 1893.

Type species. - Subscquent designation by Dall, 1870, p. 159; Litigirla clavisii M’Coy, 1851, p. 405; from the Upper Cambrian of Wales, Great Britain. Diagnosis. - The broad interpretation of LitigiiM a by Krause 6: Rowell (1975, p. 14-15) is foIlowed here.

Liwgirlella? sp. a Figs. 4A-I 0 v? 19155 Lirigiila dicellogryforiitti var. piilln

IIadding, p. 28, pl. 4, figs. 11-13. Ocf. 1963 Lirigiilella sp. 1 Wright, p. 230, pl. 1, figs. 1 4 . 0 1977 L i t i g i h dicellograproriim piilla (I Iadding), Nilsson, p. 53.

n, w,m’) Afaterial. - All specimens from ‘unit A‘ and Slandrom Limestone. Illustrated; Br128578 (W0.48, L 0.60), Br128580 (W 1.15, L 1.45), Br128579 (W 1.18, L 1.50), Br128529 (W 0.48, L 0.60). Total of 3 dorsal valves, 2 ventral valves and one complete shell (samples 12, 13, 16).

GFF I08 (1986)

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1M Lars E. Holtner

Fig. 4. MA-I. Lingidella? sp. a, ‘unit A’ sample 13 (A-E, G I ) , sample 12 (F). O A . Exterior of dorsal valve, position of I indicated, Br128580, x38. O B . Interior of A, ~ 3 8 OC. . Exterior of ventral valve, Rr128579, x38. OD. Ventral view of pedicle notch of juvenile shell, position of G indicated, Rr128578, ~ 2 3 8 OE. . Side view of

Ordovician inariiculute brachiopods

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Description. - Ventral valve with poorly developed internal area, divided into two propareas by distinct pedicle notch (Fig. 4F). Dorsal valve with poorly developed internal area. Umbonal muscle scar distinct (Fig. 4B). Both valves oval and fairly small for genus. Exteriors of both valves with ornament of fairly closely spaced concentric growth lines and well-defined protegula. Ultrastructure of shell (Figs. 4G-I) with distinct ornamentation of closely packed and irregularly shaped roughly hexagonal ‘scales’ arranged in terraces (individual ‘scales’ with maximum diameter of about 2 pm). Discussion. - Lirigitlella? sp. a is referred tentatively to the genus because it differs from the type species of Litigrilelln in the poor development of the dorsal internal area, the small size, and the apparent lack of ‘typical pitting’ on the inside of both valves (Krause 6: Rowell 1975). However, it is probable that the first two differences (and maybe the third) merely reflect the early growth stage of the specimens found. The ornamentation of hexagonal ‘scales’ is reported for the first time and clearly the detailed ultrastructure of these should b e further investigated. Curry 6: Williams (1983) described a fine (but much larger) hexagonal network of microscopic ridges on the interior shell surface of a Lower Ordovician Lingiilella. Liiigiilella? sp. a is similar (although smaller) in general shape, ornamentation and poor development of dorsal internal area to Lirigiilella sp. 1of Wright (1963) from the Upper Ordovician Portrane Limestone of Ireland. It is also comparable in general shape and ornamentation with Lirigiilella? pirlla (IIadding, 19156) from the Middle Dicellograptus Shale on Bornholm (Denmark). Distribution. - Slandrom Limestone (Og., Vg., Dal.): Fyllamosse core (51.00-51.05 m), Stora Asbotorp core (37.95-38.05 m), Fjacka section (sample D60-116).

105

Rowellella Wright, 1963 Type species. - Original designation; Rowellella miniita Wright, 1963, p. 233, from the Upper

Ordovician of Ireland. Diugnosis. - See Krause R: Rowell (1975, p. 23). Disciisriori. - T h e genus was originally assigned by Wright (1963) to the Glossellinae. O n the basis of new material described by Krause 6: Rowell (1975), it was reassigned to the Lingulellinae. However, Popov (in Nazarov 6: Popov 1980) again referred Rowellella to the Glossellinae. The material available does not give any additional indications as to its taxonomic position. The genus is not very well-known and there are few reports of it (Goryansky 1969; Biernat 1973; Popov in Nazarov 6: Popov 1976; Bednarczyk & Biernat 1978). The ultrastructure of the shell is here reportcd, for the first time, to be pitted over the entire (post-protegular) surface of both valves (Fig. 4Q). This structure is almost identical both in size and form to the normal pitting of most acrotretacean protegula (e.g., Biernat 6: Williams 1970). A n identical kind of ultrastructure is present in several previously described species; R . lariiellosa Popov, 1976 and R. riigosa Goryansky, 1969 (the material was generously supplied by L. E. Popov), in several Middle Ordovician species from Sweden (Holmer, unpublished) and in material referred to the type species R . miriiitn from the Upper Ordovician of Estonia (L. E. Popov, pers. comm. 1985).

Ro~vellellasp. indet. Figs. 4P-Q Marerial. - All specimens from Bestorp Limestone. Illustrated; Br128582 (W 0.60). Total of 5 fragmentary ventral(?) valves (samples 12, 13).

Diagnosis. - Rowellella of very elongated shape and convex anterior ventral valve profile (dorsal valve not known). Lamellose ornamentation with pitted ultrastucture. Individual shallow pits,

. Interior of ventral juvenile valve, Br128.529, X166. OG. Derail of D, position of H indicated, ~ 3 6 OF. protegular ornamentation of D, ~ 1 8 2 8 OH. . Detail of protegular ornamentation of D, X1995. 0 1 . Detail of exterior ornamentation of A, ~ 1 8 2 8 BJ-L. . ?Glossellinae gen. a spp.. ‘unit A’ (sample 12). OJ. Exterior of dorsal valve, Br128538, ~ 5 1 OK. . Exterior of ventral valve, Br128533, X.13. OL. Interior of K showing pseudointerarea, X 112. M. Acanrhanrbonia sp. indet., Slandrom Limestone (sample 16). exterior of dorsal(?) valve, Br128571, ~61. N-0. Puleritla spp.. ‘unit A’ (sample 13). ON. Ventral view of juvenile shell, Br128583, x78. 00.Detail of N showing ornamentation, X610. WP-Q. Roivellella sp. indet., ‘unit A’ (sample 13). UP. Exterior of ventral valve, Br128582, ~ 3 2 OQ. . Detail of P showing ‘pitted’ ornamentation, X1119.

106 Lars E. Holtiier

up to 3 iim in diameter, covering the entire (postprotegular) surface of the valve (Fig. 4Q).

Discirssiori. - The few fragments found do not allow a close taxonomic comparison.

Gen. a spp. Figs. U-L

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Systematic position. - ?Subfamily Glossellinae Cooper, 1956. hiriterial. - All specimens from ‘unit A’, Slandroni Limestone, and Bestorp Limestone. Illustrated; I3r128.538 (W0.60, L 0.68), Br128534 (W 0.64, L 0.87). Total of 8 dorsal valves and 2 ventral valves (samples 12, 13, 16, 17). Descriptioiotz. - Ventral valve with slim, narrow pseudointerarea (Fig. 4L). Dorsal valve without pseudointerarea. Both valves elongated oval with marginal beaks. Exteriors of both valves with concentric lamellae and fairly well defined protegula (Figs. 4J-K). Disciissiori. - The few specimens found cannot be assigned with certainty to any described genus or species known to me. The uncertain assignment to the Glossellinae is based on the absence of a distinct dorsal pseudointerarea. However, it is not comparable, either in shape and ornamentation or in the development of the ventral pseudointerarea, with any previously described member of the Glossellinae (apart from a slight similarity to the genus Paclzyglostlla Cooper, 1960). It should also be noted that the figured specimens could be juveniles. Possibly more than one species is represented in my material.

Paterrila Barrande, 1879 Systerriafic position. - Family Paterulidae Cooper, 1956. Type species. - Original designation; htertrh boherriica Barrande, 1879, p. 110, from the Middle Ordovician of Bohemia.

GFI; I08 (19S6)

(for earlier references to Paterda see Goryansky 1969, p. 52, and Cooks 1978, p. 19), especially since Cooper’s (1956) first description of etched Ordovician material (e.g., Pervical 1978; Addison 01 LockIey 5: Williams 1981; IIsvlifelr 1982). Only two recent papers include SEhl illustrations (Lockley 6: Willianis 1981; Popov et al. 1952). Popov et al. (pp. 101-103, pl. 1. Figs. 2ab) desribed and illustrated the pitted protegulum and the regular ‘net’ of rhombical ‘cells’ covering the entire shell surface on Upper Ordovician Patenrla from Estonia.

Puterulu spp. Figs. 4 N - 0 Material. - Present throughout the sequence studied. Illustrated; Br128583 (L 0.4). Total of 149 specimens (includes ventral, dorsal and complete shells; samples 11-17, 20, 21, 24). Description. - Both valves extremely thin, circular. Ultrastructure with regular ‘rhombical net’ (individual ‘rhombs’ on average 6 Itm in length and 2 prn in width) covering both valves (Fig. 40). Distinct protegula on both valves pitted (individual pits up to 4 Iim in diameter). Ventral valve with distinct pedicle notch. Discimion. - At least two species of this genus are represented among the numerous fragments found. However, these are not defined here due to the fragmented state of the material. The few more complete specimens found arc very fragile. IIenningsmoen (1938, p. 391, pl. 2,24, figs. 2 , 4 , 5) described two species, Pnterrtltr cf. boiretrtica Barrande, 1879 and P. cf. portlocki (Geinitz, 1852), from the Fjscka Shale (of the Kullatorp core, Kinnekulle, Vastergotland). These are comparable, also in age, with the material recorded here. Distribution. - Slandroni Limestone (Og., Vg., Dal.): Fyllamosse core (52.10-52.20 ni), Bestorp core (5.05-5.75 m), Fjiicka section (samples D60-118, D60-123). ‘Unit A’ (Vg.).

Diagnosis. - See Rowell (1965, p. H272).

Subfamily ACROTRETINAE Schuchert, 1893

Discussion. - Recently there has been some increase in the number of descriptions of new species referred to this rather poorly known genus

Systematic posiliorr. - Order Acrotretida Kuhn, 1949; Suborder Acrotretidina Kuhn, 1949; Superfamily Acrotretacea Schuchert, 1893; Family Acrotretidae Schuchert, 1893.

GFF 10s (1966)

Diagriosis.

- See Krause Sr Rowell (1975, p. 35).

Disciusiori. - Although an apical process is typically present among members of the Acrotretinae, it is apparently lost secondarily in cxtremely thin-shelled taxa like Hisirigerella teriiiis sp. nov. and Coriotretn? orbicirlnris sp. nov.

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Hisiqyrelln Henningsmoen, 1948 Type species. - Original designation; Atrypa? riifells fiisinger, 1837, p. 77; from the Fjiicka Shale (Lower Harjuan) of Dalarna, Sweden. Diagnosis. - Ventral valve moderately low, procline, catacline to apsacline pseudointerarea with very distinct interridge. Apical process sometimes missing or weakly developed. Dorsal valve almost flat with distinct, often protruding protegulum. Dorsal valve with well-developed pseudointerarea divided into two propareas by a deep median groove. Raised cardinal muscle scars and simple low triangular median septum. Discicssiori. - The systematic position of this problematic genus has long been in doubt (Rowell 1965, p. 11279). Mitchell (1977, p. 24) placed it within the Linnarssoninae, but in view of the new material described below this is highly unlikely. Harper (irt IIarper et al. 1984) reassigned it to the Acrotretinae and this assignment is supported here. Although a distinct apical process is generally missing in the material illustrated here, it is apparently present in closely comparable forms lower in the Middle Ordovician sequence (IIolmer, unpublished) and in H . riaria from the Middle Ordovician of the Oslo Region (Harper iri Harper et al. 1984). Comparatively few mentions of tfisirigerella have been niade since its description by IIenningsmoen (1948, p. 388), and little is known about its stratigraphic and geographic distribution (Rowell 1965; Mitchell 1977; Nilsson 1977; Cocks 1978; Harper iri Harper et al. 1984). One of the main problems in obtaining a better understanding of Hisitrgerella is the poor preservation of the type material from the Fjicka Shale. As noted by Henningsmoen (1948, p. 389) no internal features can be observed on any specimens of H. nitens from the type locality at Draggan (no longer exposed). Much additional material was collected and examined from the type locality of the Fjj5cka Shale (at Fjaeka Rivulet, Dalarna) for the present investigation, but did not yield any better preserved specimens thus making close compari-

Ordovician itiarficiilafc bracliiopodc 107

son with the new material as described here impossible. For this reason I suggest that, at least for the time being, comparisons with Hisirigerelln should be made mainly with I!. terirris as illustrated and described here. Preferably the use of the type species M. riiteris should be restricted to its occurrence in the Fjiieka Shale, until more is known about its internal characters. As defined here, the genus resembles Cotrotrefa Walcott, 1689 in some respects, but differs in, e.g., the strongly developed interridge of the ventral valve and the lack of an internally thickened pediele tube. The ventral valve of Conotretn? clevota Krause & Rowell, 1975 has a strongly developed interridge very similar to that of Ifisingerella, but the dorsal valve of this species is deeply concave with a median buttress and cannot be included with the present definition. The ventral valve of Hisirigerella is also suggestive of Girytreta Rowell, 1966 (cf. Eiirytreta cirrvnfn Rowell, 1966, p. 11). Hbirigereh differs, however, in the development of the median septum, which in Eirrytreta forms a ridge rather than a distinct septum. The genus Paratieta Biernat, 1973 is also comparable in the development of a fairly distinct ventral interridge (cf. I’nratreta ef. siriiilis Biernat, 1973, fig. 24). IIowever, the ventral valve of P. sitnilis possesses a stout apical process and the dorsal pseudointerarea is very wide and rather short. Species irtclrided. - Iiisitigere/ln rriteris (Hisinger, 1837), H. riaria (IIadding, 1913), H? davicisorii (Reed, 1917), H . hefera (Percival, 1978), H. teniris sp. nov.

Hisirigerella tetiiris sp. nov. Figs. 5A-P, 10A-C Nanic. - Latin feriiris, thin; referring to the extremely delicate shell.

Holofype. - Br128522, complete dorsal valve, Figs. 5A-G (W 1.48, L 1.26, W1 0.80, LI 0.20, Whl 0.73, LM 0.20), from Bestorp Limestone (sample 18). Paratypes. - All specimens from Bestorp Limestone. Illustrated; Br128521 (W 1.00, L 0.92, H 0.56), Br128516 (W 1.00, L 0.90, H 0.46), Br128523 (W0.33, L 0.32), Br128525 (W0.53,’L 0.53, H 0.27), Br128524 (W 0.48, L 0.45), Br128497 (damaged), Br128502 (damaged). Total of 129 dorsal valves, 122 ventral valves and 14 shells (samples 17-20).

GFF 108 (1986)

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108 Lars E. Holtner

Fig, 5. Ilisingerellu renuis sp. nov., Bestorp Limestone, sample 18 (A-N), sample 19 (0-P). O A . Holotype, exterior of dorsal valve, Br128522, ~ 3 0Ob. . Side view of A, ~ 3 2 OC. . Protegulum of A, x l l l . O D . Interior of A, ~ 3 0 0. E. Side view of interior of A, ~ 3 2 0 . F. Side view of dorsal pseudointerarea of A, ~ 8 30. G . Detail of

GFF IOS (1986)

Ordovician inarriculafe brachiopods

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Diagnosis. - Ventral valve with depressed apex, pseudointerarea catacline to slightly apsacline. Apical process missing. Mantle canal system unknown. Dorsal protegulum typically protruding. Very distinct and raised cardinal muscle scars in both valves.

109

(W 1.20-1.48, L 1.06-1.26) the muscle scars are further thickened and the dorsal pseudointerarea (WI 0.66-0.80, LI 0.16-0.20) is much widened.

Discussion. - Although H. teniris is a distinct species, its exact relationship to the type species of the genus (roughly of comparable age) is virtuDescription. - Ventral valve with maximum ally unknown. As mentioned above, this is due height just anterior to beak (Fig. 5J). External to the extremely bad preservation of the type pedicle tube drawn out to a ‘snout’ with minute material of H . tiitens, and there is little hope of foramen (Fig. 5L). Very distinctly raised ventral finding better material of this taxon from the interridge, less well-developed propareas (Fig. black shales of the type-stratum (the possibility 5L). Dorsal valve almost flat and gently sulcate exists that If. retiitis is a junior synonym of II. (Fig. 5B) on average 93% as long as wide niferu). In the type material, as illustrated by 0.59, E 0.55; n = 35). Distinct protegulum on IIenningsmoen (1948, pl. 24, figs. 6, 7) the genboth valves with cross-cutting circular, shallow eral shape of the dorsal valve, although somepits up to 3 Iim across (Figs. 5C, H). Dorsal valve what distorted by compaction, appears to be with distinct pseudointerarea on average 25 % as similar to that of If. fenutix.The maximum size of long as wide (m0.28, 0.07; n=35). Pseu- the latter is, however, much smaller (maximum dointerarea divided into two propareas by a deep width about 2.5 mm in 12. riiferu and 1.5 mm in median groove. Cardinal muscle scars on raised H . teriutis). A trace of a crushed median septum thickened platform (m0.42, 0.12; n = 8) can be discerned in most dorsal valves of the type at posterior end of median septum (Figs. 5D-F). species, but nothing else can be observed of the Ornamentation on both valves with closely dorsal interior. Even less is known about the spaced concentric fila (Fig. 5L). Shell structure ventral valve of H . nitens. All the specimens not investigated in detail, but apparently with a examined are very distorted by compaction but a middle layer of units of rectangular cross-section, well-developed ventral interridge is recognizable arranged in a ‘honey-comb’ pattern generally up (Henningsmoen 1958, pl. 24, fig. 3). The ventral to 4 pm across and of varying length (Fig. SO). valve of this species appears to be a generally somewhat lower cone with a less depressed venOritogeriy. - Specimens representing most shell- tral apex than that of H . terirris. Nothing is bearing stages in the development were found. known of the ventral interior. H . ferturis differs No specimens representing the protegular stage from all other species here referred to the genus were identified but the protegulum on older indi- in the slightly apsacline inclination of the ventral viduals is ctose to circular (WF 0.21, i 3 0.21; pseudointerarea. hficromitm (Pnterim) c h i d n = 14). In the subsequent brephic stage the shell sorii Reed, 1917 (pl. 1, figs. 1-2) from the Carais about 0.21-0.34 mm wide and 0.21-0.35 mm doc of the Girvan district show a marked similarlong (Figs. IOA-B). Here the dorsal pseudointer- ity to Hkitigerella as noted by Henningsnioen area (WI ?-0.16, LI ?-0.04) is already developed (1948, p. 389). The dorsal valve of this species, and undivided and there is a faint trace of a illustrated by Williams (1962 as Coriofrefad a d median septum. The inclination of the vental sotii (Reed), pms, pl. 6, figs. 4243, I J O I Z ,pl. 7, pseudointerarea is variable during ontogeny and figs. 1-3, 9) has raised muscle scars and a wellis initially strongly apsacline with a faint inter- developed dorsal pseudointerarea. The species is ridge (Figs. 5M-N). In juveniles (W0.34-0.70, L probably best referred to as H.? davitisorti until 0.35-0.66) a low median septum and a divided further investigated. H . teiuuris differs from the dorsal pseudointerarea (WI0.16-0.30, LI 0.01 Australian Late Ordovician H . liefera (Percival 0.08) is formed (Fig. 1OC). The adult stage (W 1978, p. 136, figs. 11A-M) which has a quadri0.48-1.20, L 0.45-1.06) is reached when the partite development of the dorsal cardinal and raised cardinal muscle scars are developed and central muscle scars and distinct mantle canal the wide dorsal pseudointerarea is formed (WI system. If. teriiris also differs from H . sp. of 0.3M3.66, L 0.08-0.16). In gerontic individuals Mitchell 1977 (p. 24, pl. 1, figs. 31-35; Ashgill of

(w

~

~~

median septum of A, ~ 8 9 . H. Dorsal protegular ornamentation,Br128523, X8SS. 0 I. Exterior of ventral valve, Br128521, X41. 0 J . Side view of shell, Br128516, X39. 0 K. Posterior view of J. X38. 0 L. Ventral interridge of J, ~ 1 1 4 Ohi. . Side view of juvenile shell. Br128525, X86. ON. Posterior view of M, X75. 00. Detail of shell structure of dorsal valve. Br128497, X1332. UP. Interior of ventral valve, Br128502, X35.

GFF 105 (1986)

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110 Lars E. ffoltner

Fig. 6.. A-H. Hiringerello sp. nov. a, 'unit A', sample 12 (A-G), sample 13 (H). OA. Exterior of dorsal valve, Br128585, X40. O B . Interior of A, ~ 4 3 OC. . Side view of interior of A, ~ 4 9 .O D . Exterior of ventral valve, BrI28586, x58. OE.Side view of D , ~ 5 60. F. Posterior view of D, ~ 5 7 OG. . Dorsal protegular ornamentation,

GFF IOS (I9S6)

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Northern Ireland) which has a distinct apical process and a much greater maximum width, and from If. t i a m (Hadding, 1913) from the Upper Caradoc of Nonvay, which also show evidence of an apical process (IIarper iii Harper et al. 1984). The ‘honey-comb’-like shell structure of H . fetiiris appears to be comparable to the pattern with longitudinal isolated tubes in the outer wall of an unnamed acrotretid illustrated by Poulsen (1971, p. 268, pl. 2, figs. 3-4; cf. Fig. 1OL herein). Disfribirriorr.- Bestorp Limestone (Vg.): Stora Asbotorp core (36.45-37.55 m), Bestorp core (1.00-5.00 m). Hisingerello sp. nov. a Figs. 6A-G

Oroi+cian inariicirlare bracliiopodr

1 11

(and smaller protegular pits). As the amount of material examined is comparatively small and rather poorly preserved, no new species is formally established. Furthermore, some of the differences stated above could be ascribed to the possible immaturity of the specimens found. Rettiarks. - Frequent fragments (c. 60 dorsal and 70 ventral valves) of a species of ifkitigerelln were found in the Slandrom Limestone (occurrences marked with a question mark in Fig. 2). It is probable that these specimens were broken during sample processing as the shells are extremely thin and fragile (probably preservational). In addition some fragmentary and compressed specimens of Hisitigrrelln (not counted) were found in the of black shale units (samples 21, 24). In none of these cases specific determination could be made.

bfaferinl.-All specimens from ‘unit A’. Illustrated; Br128585 (L 0.88), Br128586 (W 0.73, H 0.36), Br128587 (damaged), Br128612 (L 0.90). Total of 13 dorsal valves, 12 ventral valves and one shell (samples 11-13).

Disrribiitioti. - Slandrom Limestone (Og., Vg.): Fyllamosse core (50.70-51.05 m, 54.10-51.20 m). Stora Asbotorp core (38.25-38.30 m). ‘Unit A’ (Vg.): Stora Asbotorp core (38.30-38.40 m).

Dingnosis. - Characters of H . tetiiris but ventral valve more procline with much less depressed apex. Ventral interridge less pronounced. Dorsal protegulum less protruding.

Coirotretn Walcott, 1889

Description. - Ventral valve with maximum height at beak. External pedicle tube drawn out to a ‘snout’ with minute foramen (Fig. 6E) Ventral pseudointerarea procline with poorly defined interridge (Figs. 6E-F). Dorsal valve flat but gently sulcate on average 9 3 % as long as wide 0.56, L 0.52; n = 5). Sulcus starting on protegulum. Protegular ornamentation of cross-cutting shallow pits, up to 2 iim across (Fig. 6G). Dorsal pseudinterarea with median groove but comparatively short and narrow on average 20 % as long as wide (m0.31, 0.06; n = 6). Dorsal interior with poorly defined muscle scars (Fig. 6B). Median septum like that of H . fctriris.Shell structure similar to that of H. tetiub.

(w

Dkcilssion. -Although H . sp. nov. a has much in common with H. fetiuis, it differs in a number of important aspects from the latter, such as inelination of the ventral pseudointerarea, development of the interridge, development of the protegulum

Type species. - Original designation; Cotlotrefa rrlsfi Walcott, 1889, p. 365, from the Middle Ordovician of New York State. USA. Diagnosis. - See Cooper (1956, p. 247). Discilssioti. - The possibility that Cotlotrefa \Valcott is a junior synonym of Acrofreta Kutorga, 1848 has been discussed by several previous workers (Cooper 1956; Goryansky 1969; Rowell 1965; Biernat 1973; Percival 1978; Williams & Curry 1985). Although not stated explicitly by any of these workers it has become customary to treat Acrotrcfa,the type material of which is lost, as a tiottieii diibirrtn. Conotreto? orbiciilnris sp. nov. Figs. 61-P

Nntne. - Latin orbiciilnris, circular; referring to the circular outline of the shell.

Br128587, X832. 0H. Dorsal protegulum, Br1286-12, x 133. I-P. Conorrefa? orbicdarir sp. nov.. ‘unit A’ (sample 13). 01. Holotype, exterior of dorsal valve, Br128552, X52. OJ. Interior of I, X58. OK. Side view of interior of I. ~ 5 9 O . L . Protegular ornamentation of I, x1499. OM. Exterior of ventral valve, Br12880-1, ~ 6 2 . ON.Side view of hi, ~ 6 7 0. 0. Posterior view of hl, ~ 6 0U. P . Posterior view of juvenile shell, Br1285-23, X150.

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112

Lars E. Holmer

GFF 108 (1986)

ffolotype.- Br128552, slightly damaged dorsal valve, Figs. 61-L (W 0.80, L 0.80, WI 0.33, LI 0.10), from ‘unit A’ (sample 13).

Subfamily EPHIPPELASMATINAE Rowell,

Paratypes. - All specimens from ‘unit A’. Illustrated; Br128543 (W 0.30, L 0.28, H 0.16), Br128801 (W 0.72, L 0.63, If 0.47). Total of 6 dorsal valves, 5 ventral valves and 2 complete shells (samples 11-13).

Dingnosis. - Ventral valve narrowly conical, pseudointerarea catacline to strongly apsacline with indistinct intertrough. External and internal pedicle tube sometimes present, apical process frequently absent. Dorsal valve essentially flat or weakly resupinate in lateral profile. Small short propareas and concave median groove. Dorsal median septum extremely variable, trigonal, simple to very folded, very low to high, frequently with spinose anterior end and platform on posterior declivity.

Dingnosis. - Ventral valve conical, procline with wide foramen and internal pedicle tube. No apical process. Ventral pseudointerarea poorly defined. Dorsal valve flat, circular with narrow pseudointerarea, faint trace of a median buttress. Median septum low and possibly spinose. Description. - Ventral valve with maximum height at beak (Fig. 6N). Ventral pseudointcrarea poorly developed, initially apsacline in juveniles (Fig. 6P) becoming procline during subsequent growth (Fig. 6N). Well-developed external pedicle tube with wide foramen (Fig. 6P). Ventral interior lacking evidence of apical process, mantle canal system and muscle scars but with internal pedicle tube. Dorsal valve on average 91 % as wide as long (L 0.44. m 0.40; n = 6). Dorsal pseudointerarea on average 33 % as long as wide (m 0.12, 0.04; n = 3) with poorly defined anacline propareas (Figs. 6J-K). Dorsal protegulum distinct, close to circular (on average 92% as long as wide) with a raised margin. Protegula of both valves strongly pitted by crosscutting circular pits, up to 3 Iim across (Figs. 61, L). Both valves with ornamentation of concentric fila. Shell structure (not examined in detail) with a middle layer of cells with rectangular crosssection arranged in an irregular pattern, generally up to 4 Iim wide and 10 Iim long. Discilssion. - Coriotreta? orbicirlnris is not a typical member of the genus and differs from other representatives in lacking an apical process, welldeveloped mantle canal system (and a median buttress?). The presence of an internally thickened pedicle tube is, however, suggestive of Conotreln. It may well represent a new genus, but should not be established until more is known about its distribution and more detailed morphology. Dislribiitioti. - Slandrom Limestone (Og., Vg., Dal.?): Fyllamosse core (50.70-51.05 m), Stora Ksbotorp core (37.95-38.05 m), Bestorp core (5.05-5.75 m), Skultorp core (13.75-13.80 m), Fj3cka section (sample D60-116). ‘Unit A’ (Vg.): Stora Ksbotorp core (38.40-38.50 m).

1965

Discussion. - When erected, the Ephippelasmatinae Rowell (1965, p. H279) included only Ephippelnsnzn Cooper, 1956. This definition was followed essentially by Biernat (1973, p. 95). who also erected an additional subfamily, the hlyotretinae (1973, p. 80) to accornodate A l p treta Goryansky, 1969, I Jowever, a broader definition of the Ephippelasmatinae by Krause 6: Rowell (1975, p. 61) embraced the hlyotretinae. Later Bednarczyk & Biernat (1978, p. 306) also discussed (although not conclusively) the possibilty of this assignment. Popov (itz Nazarov 6: Popov 1980) described two genera, Lirrgificortzn (p. 99) and Nioiiericottzn (p. loo), that he assigned to the Ephippelasmatinae. As defined here, the subfamily includes a wide range of morphological variation (and a total of six established genera) in several characters, especially in the median septum. The unnamed Tremadocian acrotretacean illustrated (only ventral valves) by Poulsen (1971, pl. 1, figs. l a x , 2a-b, pl. 2, figs. la-b) is the oldest known member of the Ephippelasmatinae. The dorsal valve of this very interesting form almost completely lacks a median septum (IIolmer. unpublished). Getzera iiicliided. - Ephippelnsttza Cooper, 1956; hlyotreta Goryansky, 1969; unnamed acrotretncean Poulsen, 1971; Velisepfirnz Popov, 1976; Lorigilcorm Popov, 1980; Nirinericoim Popov, 1980; Rhiiiolretn I Jolmer gen. nov.

Veliseptitm Popov, 1976 Type species. - Original designation; Veliseptirtiz fragile Popov, 1976, p. 38, from the Middle Ordovician of Kazakhstan, USSR. Dingnosir. -Characters of subfamily with strongly apsacline ventral valve, narrow pseudointer-

Ordovician inarliculate brachiopods 113

GFF 108 (19x6)

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area with intertrough. Short external pedicle tube. Dorsal valve flat with narrow pseudointerarea, median groove and anacline to catacline propareas. Well-developed cardinal muscle scars. Median septum trigonal, high, sometimes with posteroventral platform and denticles on anterior declivity. Disciissioti. - When establlished by Popov (in Nazarov & Popov 1976) the genus was monotypic and included only V . fragile, characterized by a high median septum with a well-developed posteroventral platform. The above concept of Veliseptiitii has been expanded to include forms without a platform. As discussed by Biernat (1973, p. 40) and Krause 82 Rowel1 (1975, p. 33) the median septum of the acrotretids is a very variable character. Species iricliided. - Veliscpturti fragile Popov, 1976; V . strictmi Holmer sp. nov.

Velisepriirii strictirrri sp. nov. Figs. 7A-G, IOG-I Natne. - Latin strictus, straight; referring to the straight posterior margin. Huiotype. - Br128550, complete dorsal valve, Figs. 7A-D (W 0.60, L 0.40, WI 0.33, LI 0.02), from ‘unit A’ (sample 13). Paratypes. - All specimens from ‘unit A.’ Illustrated; Br128553 (W 0.42, L 0.30, H 0.17), Br128549 (W0.41, L 0.32), Br128554 (W 0.32, L 0.26), Br128528 (W 0.75, L OSO), Br128532 (W 0.37, L 0.30, H 0.20). Total of 61 dorsal valves, 16 ventral valves and 2 complete shells (samples 11-13). Diagnosis. - Dorsal valve with almost straight posterior margin, pseudointerarea short with essentially catacline propareas. Median septum with anterior denticles but lacking posteroventral platform. Description. - Ventral valve narrowly conical with apsacline pseudointerarea and intertrough. Short external pedicle tube (Figs. 7E-F). Dorsal valve on average 76 % as long as wide (L 0.32, 0.42; n = 19). Dorsal pseudointerarea on average 8 % as long as wide (m 0.24, 0.02; n = 19) with almost catacline propareas. Dorsal cardinal muscle scars, rather well-developed (Fig. 7C). Median septum simple, trigonal most frequently spinose (Fig. 7D) but sometimes lacking anterior

w

8-GFFu86

denticles. Protegulum of dorsal valve circular (WP 0.14, 0.14; n = 5 ) and rather indistinct with deep circular pits up to 1 Iim across (Fig. 7A-B). Ontogetiy. - Specimens representing most shell bearing growth stages were found. No protegular stage was found. In the early brephic stage (W 0.14-0.28, L 0.14-0.22) no trace of the median septum is present and the dorsal pseudointerarea (WI ?-0.18, LI ?-0.02) is narrow and undivided (Fig. 101). The septum makes its appearance rather abruptly during the juvenile stage (W 0.28-0.50, L 0.22-0.43, WI 0.18-0.30, LI 0.02) when the valve is about 0.40 mm wide (Figs. 10G-H). Subsequent growth in adults (W 0.500.56, L 0.43-0.46) results in the broadening of the dorsal pseudointerarea (WI 0.30-0.36, LI 0.02 (remains approximately the same during the ontogeny)) and the development of dorsal cardinal muscle scars. Disciissioti. - V. strictirtii as defined above is not much different from the type species. It is very similar in size and general structure of both valves. It differs from V. frugiie in having an almost straight posterior margin, steeply inclined dorsal propareas and in lacking, a posteroventral platform on the septum, which is also lower in V . strictimi than in V . fragile. No description was given by Popov (iti Nazarov & Popov 1976) of the protegular ornamentation in the type species. Distribution. - Slandrom Limestone (Vg.): Stora Asbotorp core (38.25-38.30 m). ‘Unit A’ (Vg.): Skultorp core (14.32-14-42 m).

Rhiriotreta gen. nov. Nattie. - Greek rfzitios, nose and tretos, perforated; referring to the external pedicle tube of the ventral valve. Type species. - Rfiitiotreta niimiilaris sp.. nov., from the Upper Viruan ‘unit A’, Gullhiigen quarry. Diagnosis. - Ventral valve catacline to apsacline with well-developed exterior pedicle tube, pseudointerarea with median trough. Dorsal valve flat with narrow, short pseudointerarea, propareas extremely narrow, anacline to catacline. Median septum very low to very high, never with platform or denticles. Both valves circular to subquadrate.

Lars E. Holmer

GFF 10s (1986)

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114

Fig. 7. A-G. Velisepfum sfricticm sp. nov., 'unit A', sample 13 (A-E), sample 12 (F), sample 11 (G). O A . Ilolotype, exterior of dorsal valve, Br128550, X89. OB. Protegular ornamentation of A, X1221. OC. Interior of A, ~ 7 4 . D. 0 Median septum of A, X 2 0 0 . 0 E. Side view of ventral valve, Br128553, x 1 1 1 . 0 F. Posterior view of

GFF I08 ( I 956)

Ordovician iriarricitlafe brachiopods

Disctissioti. - At present only the type species is included in Rhinotreta. However, several distinct species of the genus are present in the Middle Ordovician sequence of Sweden (Holmer, unpublished). Rhinotreta is distinguished from Ephippelasnza, Myotreta and Veliseptirni by its circular to subquadrate outline, simple median septum, much more narrow dorsal pseudointerarea and distinct exterior pedicle tube.

distinct subcentral node and elevated outer ridge (Fig. 75). Posterior part of ridge, slightly protruding and never covered by dorsal pseudointerarea (Fig. 7L).

Rhiriotretn m~uctilnrissp. nov. Downloaded by [Uppsala universitetsbibliotek] at 22:49 18 February 2013

Figs. 711-Q, IOD-F

Nanze. - Latin nzrrsczrlnris, muscular; referring to the distinct cardinal muscle scars. liolofype. - Br128556, complete dorsal valve, Figs. 7H-K (W 0.50, L 0.40, WI 0.18, LI 0.03, WM 0.26, LM 0.18), from 'unit A' (sample 13). Paratypes. - All specimens from 'unit A'. Illustrated; Br128555 (W0.37, L 0.36), Br128564 (W 0.37, L 0.35), Br128542 (W 0.20, L 0.20), Br128531 (W0.33, L 0.30, H 0.20), Br128537 (L 0.13, I I 0.10). Total of 205 dorsal valves, 67 ventral valves and 2 complete shells (samples 1113). Diugnosk. - Ventral valve with long, posteriorly inclined, exterior pedicle tube. Dorsal valve with very well-defined elongate cardinal muscle scars, very low median septum. Dorsal pseudointerarea very short and narrow with poorly defined anacline propareas and deep median groove. Both valves almost circular. Description. -Ventral valve with intertrough and poorly defined pseudointerarea, apsacline to catacline (Fig. 7P). Very long recurved external pedicle tube (Fig. 70). Dorsal valve on average 95 % as long as wide (L 0.32, m 0.34; n = 29). Interior with long distinct cardinal muscle scars (LM/L-ratio on average 50 lo in adults). Dorsal pseudointerarea on average 23 % as long as wide (m 0.13, 0.03; n = 29) (Fig. 7L). Median septum (ridge) very low (Fig. 7M). Protegulum on both valves with deep circular pits up to 3 pn across (Figs. 7K, Dorsal protegulum with

a).

~

115

Ontogeny. - Specimens representing most shell bearing growth stages were found. No protegular stage (m0.20, 0.17; n = 5) was identified. In the brephic stage (W0.20-0.24, L 0.174.21) a short, narrow and undivided dorsal pseudointerarea (WI0.12, LI 0.01) is present but the median septum is lacking (Figs. 10D-E). In juveniles (W 0.24-0.32, L 0.21-0.30) a faint trace of a median septum is formed and the dorsal pseudointerarea ( W I 0.12-0.14, LI 0.01-0.02) is only slightly widened. In adults (W 0.32-0.44, L 0.30-0.42, WI 0.12-0.24, LI 0.02-0.01) the dorsal cardinal muscle scars are formed as well as the low median septum. The inclination of the ventral pseudointerarea is variable during growth, initially being strongly apsacline but during subsequent growth becoming catacline (Fig. 10F). Adults can be slightly apsacline.

Distribution. - Slandrom Limestone (Og?, Vg?, Dal?): Fyllamosse core (51.00-51.05 m), Fjiicka section (sample D60-123). 'Unit A' (Vg.): Skultorp core (14.32-14.42 m).

Subfamily TORY NELASMATINAE Rowell, 1965 Diagnosis. - See Krause & Rowell (1975, p. 58). Discussion. - There is need for some revision within this subfamily. A full discussion of the problems falls outside the scope of this paper. The diagnosis of Krause 6r Rowell (1975) is tentative. It should be noted that the genus Opsicorzidiorz Ludvigsen, 1974 ( = Cnerzotretn Cocks, 1979) should be referred to the subfamily (Bitter & Ludvigsen 1979) along with Issedoriin and Pofylusmn, both of Popov, 1980. The standing of Acrotretella Ireland, 1961 is more questionable (Rowell 1965).

~

~

juvenile shell, Br128532, X 100. 0 G . Exterior of ventral valve, Br128528, X59. W 11-0. Rhiriorrero irrilrcidark gen. et sp. nov., 'unit A', sample 13 (lCO), sample 12 0 H. Holotype, exterior of dorsal valve, Br128555, ~ 9 5 0. 1 . Side view of H, X l l l . OJ. Protegulum of H, X183. O K . Protegular ornamentation of H , X666. OL. Interior of dorsal valve, Br128555, X109. OM. Side view of interior of L, X119. O N . Exterior of ventral valve, Br128564, X 114. 0 0. Side view of N, X 137. 0 P. Posterior view of juvenile shell, Br128531, X 137. 0 0. Pedicle foramen in P, ~ 5 5 5 .

(P-a).

GFF IOS (1956)

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116 Lars E. Holmer

Fig. 8. MA-G. Torynelasnia? ciirvafa sp. nov., Slandrom Limestone, sample 14 (A-C). sample 16 (D-G). CIA. Holotype, interior of dorsal valve, Br128566, ~ 8 20 . B. hledian septum of A, x 1 5 6 . 0 C. Side view of interior of A, ~ 8 1 O . D . Exterior of dorsal valve, Br128568. ~ 7 4 OE. . protegulum of D, X239. OF. Side view of ventral

GFF 10s (19S6)

Toryitelnsnin Cooper, 1956 Type species. - Original designation; Toryiielasrsma loryriiferiirii Cooper, 1956, p. 257, from the Middle Ordovician of Alabama, USA. Diagnosis. - See Rowell & Krause (1975, p. 58).

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Discilssioti. -The concept of Roivell and Krause is tentatively accepted here as additional material and comparison with Cooper’s types is needed for revision.

Torynelasntn? ciirvntn sp. nov. Figs. 8A-G, 9A-C Nuttie. - Latin ciirvatiis, bent; referring to the convex surmounting platform. Holotype. - Br128566, damaged dorsal- valve, Figs. 8A-C (L 0.50, Wi 0.19, LI 0.05), from Slandrom Limestone (sample 14). Paratypes. - All specimens from Slandrom Limestone. Illustrated; Br1285G8 (L 0.60), Br128572 (W0.38, L-0.40, H 0.38), Br 128610 (damaged), Br128641 (damaged). Total of 17 dorsal valves and 10 ventral valves (samples 14-16). Diagriosis. - Dorsal valve broadly V-shaped in lateral view with long and narrow anacline pseudointerarea. Propareas poorly defined. Strongly convex surmounting platform. Description. - Ventral valve strongly apsacline with poorly defined pseudointerarea (Figs. 8FG ) . Dorsal valve on average 9.1 5% as long as wide (m 0.36, L 0.33; n = 7). Dorsal pseudointerarea on average 21% as long as wide (m 0.14, 0.03; n = 6). Protegulum on dorsal valve poorly delineated with central groove (Fig. 8E). Protegula on both valves with distinct pitting of circular shallow pits. Large pits (up to 4 p n across) arc well separated from clusters of smaller pits (up to 360 nm across) in between. Both valves with ornamentation of concentric growth lines. Anterior end of convex surmounting platform unsupported. Anterior declivity of median septum with terrace (Fig. 8B). No evidence or muscular scars in either valve. No protegular or bre-

Ordovician irrar~icularebrachiopods

117

phic stage was found. In the juvenile stage (W 0.20-0.44, L 0.24-0.40) the curved surmounting platform and the dorsal pseudointerarea ( W I ?0.16, LI ?-0.03) are developed (Figs. 9A-C). Discilssioti. - This species is tentatively referred to Torynelmma in preference to the premature erection of a new genus. T.? crirvatn differs from all previously described spccics of the genus in the development of the dorsal pseudointerarea, which is comparatively long and narrow in T.? ciirvatn but short, wide (or less narrow) and undivided in all other species. In this respect it resembles several species referred to the genus Opsicoriidiori Ludvigsen, 1974. 0. aldridgei and 0. cellorii (Cocks 1979, pl. 13, figs. 1-8, pl- 14, figs. 1-8) in particular show a similar development of the dorsal pseudointerarea (as well as 0. podlasietzsis Biernat, 1984). Although Opsicorridiori is said to lack a well-developed surmounting platform it is interesting to note that the much laterally enlarged septa1 rods of 0. ccllorii (Cocks 1979, pl. 14, figs. 6-7) and 0. ephemera (Mergl 1982, pl. 1 , figs, 6 , 9 , 10-11) appear to be very similar to.the ‘true’ surmounting platform of Toryielnsttin. A surmounting platform occurs in species like T. tninor Cooper, 1956 (pl. 18, figs. 59-64), T. rossiciirii Goryansky, 1969 (pl. 12, figs. 15-21) and T. rariirir Biernat, 1973 (pl. 20, figs. 12-13) but the former two species differ from T.? ciirrwta in having the posterior end of this platform much broadened. Distribiirioti. - Slandrom Limestone (Vg., Dal?): Stora Asbotorp core (37.95-38.30 ni), Fj3cka section (sample D60-113).

Toryielnsnia? plarin sp. nov. Figs. 8H-N, 9D-I Nanre. - Latin ylanw, flat; referring to the flat surmounting platform. Holorype. - Br128535, complete dorsal valve, Figs. 8H-J (W 0.50, L 0.50, Wl 0.16, LI 0.02), from ‘unit A’ (sample 12). Paratypes. - All specimens from ‘unit A’. Illustrated; Br128562 (WOSO), Br12854G (W0.38, L 0.38, H 0.30), Br128544 (W 0.26, L 0.27, H

valve. Br128572, ~ 9 6 O. G . Posterior view of F, ~ 1 1 4H. IT-N. Toryrelasma? p l u m sp. nov.. ‘unit A’, sample 12 (11-J), sample 13 (K-N). 0 H. Holotype, interior of dorsal valve. Rr128535, X87. 01.Side view of interior of €i, X9J. 0 J. hledian septum of H , X200. OK. Br128562, exterior of dorsal valve, X93. O L . Protegulum of K, X216. 0 M. Oblique posterior view of shell, Br128546, x93. 0 N. Side view of hq, X93.

CFF 108 (1956)

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118 Lars E. Iloliiier

Fig. 9. rn A-C. Torynelusma? ciin’ofo sp. nov., Slandrom Limestone, sample 16 (A-B), sample 14 (C). CIA. Interior of dorsal juvenile valve, Br128640, X 126. 0 B. hledian septum of A, ~ 3 2 6 0 . C. Side view of interior of dorsal juvenile valve, Br128631. ~ 1 5 3 rn . D-I. Torynelusmu?pluna sp. nov.. ‘unit A’, sample 13 (D-G), sample 12

GFF 108 (19S6)

0.18), Br128545 (distorted), Br128536 (W 0.30, L 0.30). Total of 83 dorsal valves, 70 ventral valves and 8 shells (samples 11-13).

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Diagnosis. - Dorsal valve flat in lateral view with narrow and short anacline pseudointerarea and poorly developed propareas. Median septum trigonal with flat surmounting platform. Descripfiotr. - Ventral valve strongly apsacline with exterior pedicle tube and indistinct intertrough (Figs. SM-N). Dorsal valve flat, on average 91% as long as wide (L 0.31, W 0.34; n = 26). Interior lacking evidence of muscle scars. Dorsal pseudointerarea on average 17 % as long as wide (m0.12, 0.02; n = 26) with poorly developed and anacline propareas (Figs. 8H-I). Anterior end of flat surmounting platform unsupported. Anterior declivity of septum with terrace (Figs. 81-J). Both valves with distinct, well delineated protegulum (Fig. 9D), on dorsal valve with distinct median depression (Fig. 8L). Protegula of both valves with pitting as for T.? c~rrvatnbut pits showing cross-cutting relationship towards the edge of the protegulum (Fig. 9F). Otitogetiy. - Specimens representing all shellbearing stages of development were found. In the initial protegular stage (Fig. 9G) the shell is on average 0.20 mm wide 0.20 mm long (n = 5). There is a faint trace of a median septum and dorsal pseudointerarea. During the brephic stage (W 0.204.28, L 0.204.27) the median septum develops an upper septal rod and a short and narrow pseudointerarea (WI ?4.09, LI ?4.01) (Fig. 91). In juveniles (W0.28-0.42, L 0.27-0.36) the septal rod is laterally enlarged so as to become a surmounting platform (cf. the septal rods of Opsicotiidioti in the above discussion on T.? platia). The pseudointerarea is widened but only slightly elongated (WI0.09-0.14, LI 0.01-0.02). In adults (W 0.424.50, L 0.364.50, WI 0.140.16, LI 0.02) the anterior end of the surmounting platform becomes unsupported and a terrace is formed on the anterior declivity of the septum. In some specimens (gerontic?) there is a tendency for the septal platform to become divided anteriorly and be very slightIy convex.

Ordovician inarticulate brachiopoh 119 Discirssioti. - T.? plutru is most similar to T.? crrrvafa and should probably be referred to the same genus (see discussion of T.? cirrvafa above). The species differs from T.? crrrvata, in the development of the dorsal pseudointerarea, which in T.? platin is shorter (nlwratio 21 % (maximum LI 0.05) in T. cirrvafa, D A T ratio 17% (maximum LI 0.02) in T. platrn), in the flatness of the dorsal valve, in the mostly flat septal platform, in the development of the exterior ventral pedicle tube, and in the much coarser ornamentation of both valves of T.? platia. Disfribitfioti. - Slandrom Limestone (Vg.): Bestorp core (5.05.-5.75 m). 'Unit A' (Vg.): Stora Asbotorp core (38.30-38.40 m).

Acrotretelln Ireland, 1961 Sysfeniuficposifioti. - ?Subfamily Torynelasmatinae Rowell, 1965. Type species. - Original designation; Acrotretelln siliiriutia Ireland, 1961, p. 1139, from the Upper Silurian of Oklahoma, USA. Diagnosis. - Ventral valve broadly conical with well-developed, undivided, procline to catacline pseudointerarea. Apical process and pedicle tube absent. Dorsal valve with indistinct, undivided pseudointerarea. Median septum low to high with concave surmounting platform. Protegula on both valves distinct, bulbous on dorsal valve. Discussion. - As noted by Rowell (1965, p. H279) and Biernat (1973, p. 91), Acrofrefellais different from other members of the Torynelasmatinae in several respects and its assignment to this subfamily is still only tentative. Biernat (1973, p. 91) suggested that the ornamentation of the protegulum might give some evidence regarding its taxonomic position. As desribed below the pitting of the protegulum in A . sp. a (Fig. 9N) is much different from what is considered typical of the subfamily (cf. Fig. 9F) and appears to be more similar to members of the Acrotetinae. The character of the protegular pitting in the type species A . silnriana has not yet been

(H-I). OD. Oblique posterior view of juvenile shell, Br12854-1, X132. OE. Detail of posterior margin of D, ~ 3 3 3 OF. . Ventral protegular ornamentation of D, ~ 1 9 9 8 O . G . Oblique posterior view of protegular shell, Br128545, X165. OIL Interior of dorsal juvenile valve, Br128536, X 158. 0 I . hledian septum of 11, X.171. W J - 0 . Acrotrefellasp. a, Bestorp Limestone, sample 19. 0 J. Exterior of dorsal valve, Br128505, 92. 0 K . Exterior of ventral valve, Br128.506, ~ 8 9 OL. . Side view of K, xlOS. Ohl. Posterior view of K, ~ 9 2 ON. . Protegular ornamentation of K, X1998. 00. Interior of dorsal valve, Br128520, X89.

GFF I08 (1986)

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120 Lars E. IIolrner

Fig. 10. I A - C . Hisingerello renuis sp. nov., nestorp Limestone (Sample 18). O A . Exterior of dorsal juvenile valve, Br128523, X134. 0 B. Interior of A, X139. OC. Side view of interior of dorsal juvenile valve, Br12852.1, X96. H D-F. Rhinorreto tniuculurb gen. et sp. nov., ‘unit A’, sample 13 (D-E), sample 12 (F). 0 D. Exterior of

Ordovician inarticulate brachiopods 121

studied. The distribution and morphology of this genus must be investigated further. This is the first report of the genus from the Ordovician. Species ineliided. - Acrotretella silirriaria Ireland, 1961.

Acrotretelh sp. a

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Figs. 9J-0 Material. - All specimens from Bestorp Limestone. Illustrated; Br128506 (W0.48, L 0.38, I-I 0.21), Br128505 (W0.48, L 0.40), Br128520 (L 0.40). Total of two dorsal valves and three ventral valves (samples 17, 19). Diagnosis. - Pedicle foramen comparatively large. Dorsal valve concave with very short, poorly developed pseudointerarea. Dorsal interior with median septum and concave surmounting platform. Description. - Ventral valve with well-developed, flat, catacline pseudointerarea lacking intertrough (Fig. 9L-M). Dorsal valve with an extremely low median septum and trace of a concave surmounting platform (Fig. 9 0 ) Protegula on both valves distinct (Figs. 9J-K) and pitted. Protegular ornamentation with deep and circular pits (up to 1 pm across) of uniform size and showing cross-cutting relationships (Fig. 9N). Ornamentation on both valves with indistinct concentric rugae (Fig. 9L).

Discussion. - This is the second species assigned to the genus and can be compared only with the type species. The latter is very similar in many characters, such as, the general outline of both valves, the development of the bulbous dorsal protegulum. A . sp. a differs from A . silirriarza in having a much weaker ornamentation, larger pedicle foramen and a shorter dorsal pseudointerarea. Possibly only juveniles are represented in the figured material and consequently no new species is named. A specimen (not illustrated) originating from a loose boulder (possibly from the Slandrom Limestone) probably represents an adult stage (W 0.62, L 0.51) of A . sp. a. In this

dorsal valve a very high median septum with a distinctly concave surmounting platform is developed, as well as two elevated muscular platforms. The formal establishment of this extrernely rare species is postponed until more material has been isolated. Distribiifiori. - Bestorp Limestone (Vg.). Slandrom Limestone (Og., Vg.): Fyllamosse core (54.40-54.50 m), Bestorp core (5.05-5.75 m).

Scaplielmrria Cooper, 1965 Sysferizaficposition. - Subfamily Scaphelasmatinae Rowell, 1965. Type species. - Original designation; ScapheIastiia septafitr,i Cooper, 1956, p. 259, from the Middle Ordovician of Alabama, USA. Diagnosis. - See Biernat (1973, p. 85).

Scaplielamia ntica Popov, 1975 Figs. 1OJ-0 01975 Scaphelasina mica Popov, p. 39, pl. 5, figs. 21-30. Materid. - All specimens from ‘unit A’. Illustrated; Br128547 (W 0.57, L 0.42), Br128540 (W 0.50, L 0.38), Br128541 (W 0.28, L 0.20, I I 0.10). Total of 17 dorsal valves, 10 ventral valves an,d one complete shell (samples 12-13). Diagnosis. - See Popov (1975, p. 39). Description. - For macroscopic characters see Popov (1975, p. 39). Protegula on both valves with typical pitting of subfamily with large circular pits (up to 3 pm across), well separated by ridges and clusters of small pits (up to 600 nm across). Shell structure apparently with a middle layer of longitudinal cells of rectangular crosssection (Fig. 1OL). Dkcirssiori. - S. mica as illustrated here appears to be indistinguishable from specimens of the

dorsal juveXile valve, Br1285-12,X187. OE. Interior of D, X187. OF. oblique posterior view of juvenile shell, Br128537, XIOS. G-I. Veliseptumstricmm sp. nov., ‘unit A’ (sample 13). G.Extcrior of dorsal juvenile valve, Br128519, xlOS. OH. Interior of G, XlOS. 0 1 . Interior of dorsal juvenile valve, Br1285S4, X139. UJ-0. Scuphelarma mica Popov 1975, ‘unit A’, sample 13 (J-L), sample 12 (M-0).OJ. Exterior of dorsal valve, Br1285.17,~ 7 8 OK. . Interior of J. X81. OL. Detail of shell structure on interior of J, X69-1. Ohl. Exterior of ventral valve, Br1285-10,X90. 0 N. Side view of juvenile shell, Br128541, X195. 00. Ventral view of N, X156.

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122 Lars E. Ifolnier

GFF 10s (1956)

Fig. 11. HA-D.Schizotrera spp. Slandrom Limestone (sample 15). O A . Exterior of dorsal valve, position of B indicated, Br12859.1, ~ 3 . 1 O . B . Detail of A, showing ornamentation of ‘pits’, position of C indicated, ~ 4 3 00 . C. Detail of A showing ‘deformed’ bands of ‘pits’, X1257. O D . Exterior of ventral valve, Br128595, X59. HE-G. Eoconulus cf. clivosus Popov, 1975, ‘unit A’ (sample 13). 0 E. Exterior of dorsal valve, Br1285.18, x 121. 0 F. Side view of E, X131. OG. Detail of E showing protegular ornamentation, X572.

species from Middle Ordovician Bestamak Formation of Kazakhstan (material generously supplied by L. E. Popov). However, the maximum size of S. rnicn in my collections is smaller compared with the type material (holotype, complete shell; (W 0.94, L 0.80), Popov 1975, pl. 5, figs. 21-30). Probably, all specimens illustrated herein represent juveniles. Distribiifion. - Slandrom Limestone (Og., Vg., Dal.): Fyllamosse core (51.70-51.75 m, 53.8054.50 m), Stora Asbotorp core (38.25-38.30 ni), Skultorp core (13.75-13.80 m), Bestorp core (5.055.75 m), Fjicka section (D60-118, D60123). ‘unit A’ (Vg.).

Eocoiiulits Cooper, 1956

Diagnosis. -See Krause & Rowell (1975, p. 64). Discicssion. - The genus was originally placed within the (calcareous) Craniacea. Rowell(l965, p. H291) supported this placing but later Krause & Rowell (1975, p. 64) tentatively assigned it to the Acrotretacea. An exhaustive summary as to previous works on Eoconiilils was also compiled by these authors. Species itzchtded. - For list before 1975, see Krause & Kowell (1975). Eoconiiliis clivosrcs Popov, 1975, Eocorzirlils dynzietzsis Bednarnyk & Biernat, 1978.

Eoconiiliis cf. clivosils Popov, 1975 Figs. 11E-G

Systertzntic position. - ?Superfamily Acrotretacea Schuchert, 1893; Family Eoconulidae Rowell, 1965.

Ainterinl. -All specimens from ‘unit A’. Illustrated; Br128548 (W 0.38, L 0.31). Total of 2 dorsal valves (sample 13).

Type species. - Original designation; Eocorziilirs

Dingnosis. - See Popov (1975, p. 41).

recrangiilntiu Cooper, 1956, p. 282, from the

Middle Ordovician of Alabama, USA.

Descripriori. - For macroscopic characters see

GFF I08 (1956)

Popov (1975, p., 41). Protegulum on dorsal valve well-defined with distinct pitting of circular and very shallow pits (up to 9 p n across) showing cross-cutting relationships (Fig. 1 IG).

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Disciusion. - Only juvenile specimens were found in my material, making close comparison with other taxa difficult. The shape and ornamentation resemble those of E. clivosris from the Middle Ordovician of Kazakhstan, to which the Swedish specimens are referred tentatively. Distribritiori. - Slandrom Limestone (Dal.): Fjacka section (samples D60-122, D60-123). ‘Unit A’ (Vg.).

Schizotreta Kutorga, 1848 Systernaric positio,i. - Superfamily Discinacea Gray, 1840; Family Discinidae Gray, 1840; Superfamily Orbiculoideinae Schuchert, 1929. Type species. - Original designation; Orbiciila elliptica Kutorga, 1846, p. 123, from the Middle Ordovician of Bohemia. Diagnosis. - See Rowell (1965, p. H275).

Schirotretn spp. Figs. 11A-D hfaterial. - Present throughout the sequence studied. Illustrated; Br128594 (damaged), Br128595 (W 0.80, L 0.80). Total of 7 dorsal valves and 3 ventral valves (samples 13-16, 1819, 21,24).

Ordovician inarticulaie brachiopods

123

first time from this group. Similar pitting has been found in Schizotreta spp. and Orbicziloidea? spp. from the Middle Ordovician of central Sweden and in Recent Dirciniscn lntmdlosa (Broderip) from South America (IIolmer, unpublished) .

Acniithniii boiiin Cooper,

1956

Systematic position. - Superfamily Siphonotretacea Kutorga, 1848; Family Siphonotretidae Kutorga, 1848; Subfamily Acanthamboniinae Cooper, 1956. Type species. - Original designation; Acanthartiboiiia rniizrAssinza Cooper (1956, p. 211), from the Middle Ordovician of Alabama, USA. Diagnosis. - See Rowell (1956, p. H269). Disciusiorz. - HavliEek (1982, p. 73) suggested that Acantlranzbonia should be reassigned to the Siphonotretacea on the basis of the many features in common with the genus Helnzersetzia Pander. The main argument against such a placing would be the lack of a pedicle tube in Acuntliambonia. However, Popov (pers. comm. 1985) reported the presence of a minute pedicle foramen (20-25 pm across) in specimcns of A . portranensis Wright and such a tube appears to be present also in A . ininiitissinra Cooper (pl. 18, fig. 25) and in Acnritlzarnboniasp. from the Middle Ordovician of Sweden (Holmer, unpublished).

Acaritlintiiboiiia sp. indet. Fig. 4M

Description. - Dorsal valve flattened. Ventral valve slightly conical. Ventral interior with low posterior ridge and pedicle tube. Protegula on both valves smooth. Remainder of both valves with ornamentation of regularly spaced concentric rugae, distinctly pitted (Fig. 11B) with almost circular shallow pits (up to 860 nm across). On one specimen (Br128591), several narrow areas show a disruption in the development of ‘normal pits’, to create bands (Fig. 11C) of larger elongated pits (up to 3 pm long and 2 p n across). Disciusiori. - Several species are present in the material but are not established formally here, as additional material is needed. However, the presence of pits, distributed over the entire shell surfaces (except protegula) is described for the

hfaterial. -All specimens from ‘unit A’ and Slandrom Limestone. Illustrated; Br128571 (W 0.47, L 0.43). Total of 2 dorsal valves (samples 12, 16). Discussion. - Neither of the specimens are sufficiently well preserved to allow any closer comparison with established species of the genus. Acknodedgernents. -This study was carried out at the Institute of Palaeontology, Uppsala. V. Jaanusson (Stockholm) and S. Bengtson (Uppsala) kindly helped, encouraged and offered constructive criticism throughout the study. I am grateful to A. J . Rowell (Lawrence), D. A. T. Harper (Galway) and L. E. Popov (Leningrad) for comments on the manuscript. I also thank M. G. Bassett (Cardiff) who corrected the language and offered comments on the manuscript in various stagcs in its development. Y. Grahn (Uppsala)

124 Lars E. Holmer

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kindly supplied his samples from pertinent parts of boring cores (owned by the Geological Survey of Sweden). J. Johansson (Skollersta) supplied important material from his extensive collections. The assistance of hi. Lindell (Uppsala) in the laboratory work and T. Westberg (Uppsala) in the dark-room work is appreciated. The CEhlENTA AB kindly gave access to Gullhogen quarry. The work was supported by grants from the Royal Swedish Academy of Science (Gustaf Lindstroms Minnesfond, Hierta-Retzius Stipendiefond), Uppsala University (Liljewalchs Resestipendiefond) and Department of Palaeozoology, Swedish hluscum of Natural History. The paper was printed with financial support from the CEMENTA AB and Erik Stensib Palaeozoology Fund.

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