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BROCK, G.A. 1998. Middle Cambrian molluscs from the southern New England Fold Belt, New South Wales,. Australia. [Mollusques du Cambrien moyen de la ...

MIDDLE C A M B R I A N M O L L U S C S FROM THE S O U T H E R N N E W E N G L A N D FOLD BELT, N E W S O U T H WAI,ES, AUSTRAI,IA GLENN A . B R O C K

BROCK, G.A. 1998. Middle Cambrian molluscs from the southern New England Fold Belt, New South Wales, Australia. [Mollusques du Cambrien moyen de la chalne gGosynclinale de la Nouvelle-Angleterre du Sud, NouvelleGalles du Sud, Australie]. GEOBIOS, 31, 5: 571-586. Villeurbanne, le 31.10.1998. Manuscrit dGpos6 le 01.04.1997; accept6 dGfinitivement le 30.06.1997. ABSTRACT - Middle Cambrian (Floran-Undillan) allochthonous limestone clasts from the Murrawong Creek Formation, southern New England Fold Belt, northeastern N.S.W., Australia, yield a well preserved silicified molluscan fauna consisting of the helcionelloids Latouchella accordionata RUNNEGAR& JELL,Latouchella aliciae nov. sp., Yochelcionella daleki RUNNEGAR& JELL,Anabarella simesi MACKINNON,and the paragastropod Pelagiella sp. cf. P. deltoides RUNNEOAR& JELL. On the basis of a single bellerophontiform-like muscle scar fortuitously preserved in one specimen, Protowenella is tentatively re-interpreted as an archaeogastropod, though a tergomyan affinity cannot be ruled out. The fauna displays strong regional affinities with the "first discovery limestone" member of the Coonigan Formation, western N.S.W., sequences in the Georgina Basin, northern Australia, and northwest Nelson in New Zealand. KEYWORDS: MOLLUSCA, MIDDLE CAMBRIAN, AUSTRALIA, HELCIONELLIDA, PARAGASTROPODA, ARCHAEOGASTROPODA RI~SUMt~ - Des clastes de calcaires allochtones du Cambrien moyen (Floren-Undillen) de l'Gchelle stratigraphique du Murrawong (chalne gGosynclinale de la Nouvelle-Angleterre du Sud (Nouvelle-Galles du Sud, Australie) ont fourni une faune silicifiGe de mollusques en bon 6tat de conservation contenant les espGces helcionelloides Latouchella accordianata RUNNEOAR& JELL, Latouchella aliciae nov. sp., Yochelcionella daleki RUNNEGAR& JELL,Anabarella simesi MAcKINNONet le paragastGropode Pelagiella sp. cf. P. deltordes RUNNEGAR& JELL. Se basant sur une seule impression musculaire bellerophontiforme conservGe fortuitement dans un seul specimen, Protowenella est rGinterprGt6 provisoirement comme un archGogastGropode, sans toutefois exclure la possibilit6 d'une affinit6 tergomyenne. La laurie montre de nettes affinitGs rGgionales avec le membre "calcaire de la premi6re dGcouverte" de l'Gchelle stratigraphique Coonigan (Ouest de la Nouvelle-Galles du Sud) et avec des sGquences du Bassin Georgina du Nord de l'Australie et du Nord-Est de Nelson, Nouvelle-ZGlande. MOTS-CLI~S: MOLLUSCA, CAMBRIEN MOYEN, AUSTRALIE, HELCIONELLIDA, PARAGASTROPODA, ARCHt~OGASTROPODES. INTRODUCTION

C a m b r i a n u n i v a l v e d m i c r o m o l l u s c s are well r e p r e s e n t e d in A u s t r a l i a , w i t h f a u n a s described f r o m c a r b o n a t e s e q u e n c e s in S o u t h A u s t r a ] i a ( R u n n e g a r

in Bengtson et al. 1990), western Queensland (Runnegar & Jell 1976), New South Wales (Runnegar & Jell 1976), and the Northern Territory (Kruse 1990, 1991). These occurrences come from a wide spectrum of carbonate environments, including supratidal to platformal and shelf facies, deposited in shallow water intracratonic basins. Runnegar (1996) noted that many of the taxa, originally described from Australia are now known to

h a v e a s e m i - g l o b a l or global d i s t r i b u t i o n a n d h a v e b e c o m e useful a d j u n c t s to C a m b r i a n b i o s t r a t i g r a phic a n d p a l a e o b i o g e o g r a p h i c a n a l y s e s . T h i s p a p e r d o c u m e n t s t h e m i c r o m o l l u s c a n f a u n a f r o m allocht h o n o u s l i m e s t o n e clasts of t h e M u r r a w o n g C r e e k F o r m a t i o n (Cawood 1980), in t h e s o u t h e r n N e w E n g l a n d Fold Belt of n o r t h e a s t e r n N e w S o u t h Wales. T h i s f o r m a t i o n is i n t e r p r e t e d as a s u b m a r i ne t u r b i d i t e u n i t s o u r c e d f r o m a n active i n t r a oceanic i s l a n d arc w i t h f r i n g i n g c a r b o n a t e p l a t form, s i t u a t e d to t h e e a s t of t h e A u s t r a l i a n c r a t o n d u r i n g t h e Middle a n d L a t e C a m b r i a n (Leitch & Cawood 1987, 1996). I n t h i s r e s p e c t t h e s e t t i n g is s i m i l a r to a n u m b e r of o t h e r "exotic", a c c r e t e d t e r -

572 ranes from New South Wales (Bischoff & Prendergast 1987) and New Zealand (MacKinnon 1985). GEOLOGICAL S E T T I N G The New England Fold Belt extends for approximately 1300 km along the east coast of Australia (Fig. 1A), and is generally interpreted as the site of a major convergent plate margin (Cawood 1980, 1983; Leitch et al. 1988; Lindsay 1990; Leitch & Cawood 1996). The earliest phase of convergence was initiated in the Cambrian, and the original presence of magmatic arc rocks is indicated by volcaniclastic debris in a 1700 m thick sequence of debris flow conglomerates, turbidites, hemipelagJc siliceous siltstones and thin ash fall tufts in the Murrawong Creek-Copes Creek area (Leitch & Cawood 1996). The oldest unit in this sequence, the Murrawong Creek Formation (Cawood 1980), crops out as a 4.5 km north-south trending tract of interbedded siltstone, sandstone and conglomerate on the western side of the Peel Fault System, approximately 25 km SSE of Tamworth in the southern New England Fold Belt (Fig. 1B,C). In the type section, along Murrawong Creek, the sequence consists of 450 m of poorly outcropping, interbedded coarse to fine conglomerates and sandstones. The base of the section is faulted against undifferentiated ?Devonian metasediments (Fig. 2). Leitch & Cawood (1987, fig. 2) recognised three conglomerate horizons in the Murrawong Creek Formation, informally designated Units 1-3. Unit 1, the coarsest of the three units (Fig. 2), is a poorly outcropping, approximately 85 m thick, polymictic paraconglomerate with angular to subrounded, mostly volcanic, clasts (0.01-1.5 m in diameter) set in a poorly sorted sand- to granule grade volcaniclastic matrix, with the largest clasts represented by fossiliferous limestones. These are the source of the molluscan fauna described herein. The associated shelly fauna from the limestone clasts is dominated by miomeroid and polymeroid trilobites (Cawood 1976; Sloan 1991; Sloan & Laurie in prep.), and lingulate brachiopods (Engelbretsen 1996), with minor components including, articulate brachiopods (Brock in press), an enigmatic coral-like organism (Engelbretsen 1993), and a diverse array of small shelly fossils currently in the process of being described. The Murrawong Creek Formation is conformably overlain by approximately 900 m of argillites, cherts, tufts, sandstones and fine conglomerates of the Pipeclay Creek Formation (Cawood 1980; Leitch & Cawood 1987). Leitch & Cawood (1987), in a detailed provenance study of the cobble- and pebble-sized igneous

FIGURE 1 - A. Generalisedmap ofAustralia showingextent of rocks associated with the New England Fold Belt. B. GeneraIised map showing exposures of the southern New England Fold Belt and the locality of the Murrawong Creek area. C. Geologicalmap of the MurrawongCreek-Copes Creek area (modifiedafter Leitch & Cawood 1987). Black box shows area where twenty one allochthonouslimestoneclasts were recollected in 1993-4 from Cawood's (1976) original L1 locality, Unit 1 in Murrawong Creek. ~L Carte g~ndrale de FAustralie indiquant l'dtendue des roches [email protected] & la cha~ne gdosynclihale de la Nouvelle-Angleterre. B. Carte g~ngrale indiquant les affleurements de la chaZne gdosynclinale de la NouveIleAngleterre du S u d et la [email protected] du Murrawong. C. Carte gdologique de la rggion du Murrawong et du Cope [email protected] d'[email protected] Leitch & Cawood 1987), L'encadrd noir indique le site oit furent recueillis en 1993-4 vingt et un clastes allochtones calcaires de la localitg originelle L1 de Cawood (1976), Unitd 1 dtt

Murrawong.

clasts from the Murrawong Creek Formation, found t h a t the proportions of components, mineral chemistry, major trace element composition and absence of detritus characteristic of continental crust indicated derivation from a low-K tholeiitic suite t h a t ranged in composition from basalt to rhyolite, with andesite probably the

573

PIPECLAY CK. FORMATION -

The molluscs reported herein were acid etched from twenty-one al]ochthonous limestone clasts recollected from Cawood's (1976) original L1 locality (Fig. 1C), unit 1 in Murrawong Creek. (grid ref. 1987 3524 Wootomin 1:25,000 topographic sheet 9135-111-N).

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into "relatively deep water conditions" (Leitch & Cawood 1987, p. 635) from an u n k n o w n or eroded western source (Leitch & Cawood 1987; Leitch et al. 1988).

allochthonous limestone clasts with Middle Cambrian molluscs (= Cawood's L1 locality)

,

FIGURE 2 - T y p e s e c t i o n of t h e M u r r a w o n g C r e e k F o r m a t i o n , a l o n g M u r r a w o n g C r e e k (g. 1= 200354-190350) s h o w i n g s a m pled c o n g l o m e r a t e horizon, U n i t 1 of Leitch & Cawood 1987 (= Cawood's 1976 L1 locality). Modified after Leitch & Cawood (1987, fig. 2). Coupe type de la cha~ne gdosynclinale le long du

Murrawong (rdf. de grille 200354 - 190350) montrant l'horizon de conglomdrat dchantillonnd, Unitd 1 de Leitch & Cawood (= la localit# L1 1976 de Cawood). Modifide d'apri~s Leitch & Cawood (1987, fig. 2).

most common component. This finding is consistent with an interpretation t h a t the rocks were derived from an intra-oceanic island are, rather t h a n a continental margin arc. The allochthonous volcaniclastic debris (including the limestone clasts) of the Murrawong Creek Formation and the conformably overlying Pipeclay Creek Argillite were probably deposited as gravity flows

AGE

OF THE

MURRAWONG

CREEK

FOR-

MATION

Cambrian trilobites were originally reported by Cawood (1976), but the bulk of the trilobite assemblages were described by Sloan (1991), who determined the limestone clasts ranged in age from Floran (atavus-opimus zones) through the Undillan (punctuosus-nathorsti zones) into the early Boomerangian (L. laevigata Zone) of the A u s t r a l i a n Middle C a m b r i a n stage scale (Shergold 1995). The absence of trilobites representative of the L. laevigata Zone in the clasts containing the molluscs is consistent with a slightly narrower age range spanning the FloranUndillan Stages, atavus-punctuosus zones. It should be noted however t h a t Sloan (1991, p.10) noted the co-occurrence "within a single homogeneous clast of forms previously reported from different zones" indicating t h a t several tax a, at least in Australia, probably have longer stratigraphic ranges t h a n previously reported. Though a Middle Cambrian age for the a]lochthonous clasts has never been doubted, the age of the enclosing matrix of the Murrawong Creek Formation has been the subject of some controversy. Cawood (1976, 1980) indicated the age of the clasts and enclosing matrix were probably similar. However, some authors suggested a possible Silurian to Devonian age for the conformably overlying Pipeclay Creek Formation based on the identification of the radiolarian genus Ceratoikiscum and a number of poorly preserved spheroidal radiolarians with r e m n a n t three-bladed spines (Aitchison et al. 1992; Flood & Aitchison 1992). The Cambrian age of the unit was recently verified by Stewart (1995) who reported the discovery of an assemblage of paraconodonts including Muellerodus, Herzina, Prooneotodus and Furnishina, and a number of minute forms similar to Clavohamuhts and Westergaardodina from a dark, thinly bedded, spiculitic chert of the Pipeclay Creek Formation in Copes Creek. The abundance of paraconodonts and the lack of euconodonts is consistent with a Middle to early Late Cambrian age for this formation. Therefore, the

574 conformably underlying Murrawong Creek Formation must have been deposited during the midlate Middle Cambrian. SYSTEMATIC

PALAEONTOLOGY

All type and paratype (figured and unfigured) specimens are housed in the collections of the Australian Museum and have been assigned AMF numbers. Phylum MOLLUSCACuvier, 1797 - In a major re-evaluation of early molluscan phylogeny Runnegar & Pojeta (1974, 1985), Pojeta & Runnegar (1976) and Runnegar & Jell (1976) erected a new systematic hierarchy that differed substantially from that of earlier authors, especially as outlined in the Treatise on Invertebrate Paleontology (Knight et al. 1960). Central to this new scheme was a broad concept of the Class Monoplacophora housing a diverse range of untorted, bilaterally symmetrical orthoconic, cyrtoconic and planispiral molluscs assumed to have an anterior mouth and posteriorly located anus. This concept of the Class Monoplacophora has recently been challenged by a number of authors who have recommended the term "Monoplacophora" be abandoned oi; at the very least, be restricted to molluscs of the Suborder Tryblidiina Wenz 1938 (Salvini-Plawen 1980; Wingstrand 1985; Peel 1991a,b; Geyer 1994). Many of the groups originally included in the Class Monoplacophora sensu Runnegar & Pojeta (1974) have been isolated into separate orders or have been elevated to class level, such as the Tergomya and Helcionelloida (Peel 1991a,b). Discussion

The higher level classification and phylogenetic relationships of early Palaeozoic molluscs is currently undergoing vigorous debate. A detailed examination of the debate is beyond the scope of the present paper, but comprehensive reviews of the various disparate viewpoints pervading early molluscan phylogeny and palaeontology are presented by Runnegar & Pojeta (1974, 1985), Runnegar & Jell (1976, 1980), Pojeta & Runnegar (1976), Harper & Rollins (1982), Hornp (1991a,b), Peel (1988, 1991a,b), Wahlman (1992), Berg-

Madsen & Peel (1978, 1994), Geyer (1994), Riedel (1996) Winnepenninckx et al. (1996), Lindberg & Ponder (1996) and Runnegar (1996). Class HELCIONELLOIDAPeel, 1991a D i a g n o s i s - See Peel (1991a, p. 173).

D i s c u s s i o n - Runnegar & Jell (1976) transferred all members of the Order Bellerophontida, many of which were traditionally considered to be prosobranch gastropods (e.g. Bellerophon and Sinuites - Knight 1947, 1952; Yochelson 1967; Peel 1972), to the Class Monoplacophora. Berg-Madsen & Peel (1978) drew attention to some of the problems associated with this broad classification and suggested that it included a mixture of untorted monoplacophorans and torted gastropods. Harper & Rollins (1982) restricted the Class Monoplacophora to the tryblidioid lineage. Peel (1991a,b), following the recommendations of Harper & Rollins (1982) and Wingstrand (1985), abandoned the Class Monoplacophora, and transferred various taxa to the Gastropoda, the Tergomya and his new Class Helcionelloida. The latter Class was erected to house a major lineage of untorted, endogastrically coiled univalved molluscs. Despite the fact that some authors, notably Runnegar (1996) and Riedel (1996), continue to qnestion the validity of this higher level classification, others such as Geyer (1994) have accepted the classification, though with some modification. Order HELCIONELLIDAGeyer, 1994 Family HELCIONELLIDAEWenz, 1938 Helcionellidae gen. et sp. indet. Fig. 3.1-3

D e s c r i p t i o n - Poorly preserved, apparently smooth, low, cyrtoconic univalves with less than one whorl. Supra-apical shell surface wide, with gentle convexity; short sub-apical shell wall between curved apex (broken) and flared posterior apertural rim. Discussion - The fragmentary nature of the shells and overall poor preservation makes precise tax onomic assignment impossible. The shells are certainly helcionelliform in appearance (Fig. 3.1-3) and

FIGURE 3 - 1-3. Helcionellida gen. et sp. indet., 1, lateral, 2, antero-dorsal and 3, posterior views of AMF97387, from clast W/L1/S4, Ix 40]. 4-6. Latouchella accordionata RUNNEGAI~& J~LL. 4, lateral view of AMF97388, from clast W/L1/S4, [x 45]. 5, lateral view of AMF97389, from clast W/L1/S4, [x 35]. 6, lateral view of AMF97390, from clast W/L1/S4, Ix 35]. "/-12. Latouchella aliciae nov. sp. 7-9 all AMF97395, from clast W19.7, lateral view of adult shell, Ix 18]; 8, apertural view, Ix 18]; 9, close-up of posterior exhalant ridges on inner shell wall, [x 42]. 10-12, lateral, dorsal (both Ix 30]), and close-up views of anterior rugae [x 65] of holotype, AMF97394, from clast W/L1/S4. 1-3. Helcionellida gen. et sp. indgt., en vues 1, latgrale, 2, antgro-dorsale et 3~ postgrieure de AMF97387, du claste W/L1/$4~ Ix 40]. 4-6. Latouchella accordionata RUNNEGAR • JELL. 4, r u e latgrale de AMF97388, du elaste W / L 1 / $4, Ix 45]. 5, vue lat~rale de AMF97389, du claste W / L 1 / $4, Ix 35]. 6~ rue lat~rale de AMF97390, du claste W / L 1 / $4, Ix 35]. 7-12, Latouchella aliciae nov. sp. 7-9 tous AMF97395, du claste W19. 7, vue latgrale de la coquille adulte, [x 18]; 8, vue aperturale, x 18; 9, gros plan des striations post~rieures exhalantes de la paroi interne, Ix 42]. 10-12, rues lat~rale Ix 30], dorsale [x 30] et gros plan des rugae antgrieures (x 65) de l'holotype, AMF97394, du claste W / L 1 / $ 4 .

575

576 display some similarity to smooth silicified forms assigned to gen. et sp. indet, by Runnegar & Jell (1976, figs 9A, 10-11) from the Middle Cambrian Currant Bush Limestone, N.W. Queensland. M a t e r i a l - 19 specimens from clasts, W1, W3, W38, W/L1/S1, W/L1/S4, W/L1/S6

Genus L a t o u c h e l l a COBBOLD,1921 T y p e s p e c i e s - Latouchella costata COBBOLD,1921. - The traditional concept of' LatoucheIIa as an untorted exogastrically coiled mollusc

Discussion

promulgated by Pojeta & Runnegar (1976, fig. 6D) and Runnegar & Jell (1976) has been challenged in recent years, so that this genus, and all other helcionellid univalves, are now commonly reconstructed as untorted molluscs with an endogastrically coiled shell (Geyer 1986; Peel & Yochelson 1987; Peel 1991a,b). Peel (1991b) interpreted the paired internal ridges of Latouchella as reflecting folds in the overlying soft tissue of the mantle cavity wall separating laterally located inhalant water currents from the median exhalant current, thus voiding at the apertural rim of the posteriorly directed, sub-apical shell surface. While it is acknowledged that valid arguments exist for both exogastric and endogastric shell interpretations, the latter is followed here for helcionelloids.

nata from the "first discovery limestone" member

of the Coonigan Formation, western N.S.W. described by Runnegar & Jell (1976, Fig. 10C, 1-18, non 11). Conspecific material has also been recovered from early Middle Cambrian sequences in the Daly Basin (Kruse 1990), and the northern Georgina Basin (Kruse 1991). MacKinnon (1985, p. 68) referred some steinkerns from the Middle Cambrian Tasman Formation, New Zealand to L. sp. cf. L. accordionata, but the degree of whorl is somewhat less than that of typical L. accordionata, and the New Zealand specimens appear to be more laterally compressed. As such, this assignment must be viewed with some caution. Evans (1989) described L. cf. L. accordionata from the Lower C a m b r i a n Shackleton L i m e s t o n e of Antarctica, but this report (part of an unpublished Master's thesis) has yet to be evaluated. If the latter report is proven, L. accordionata would have a stratigraphic range from Lower Cambrian to the middle Middle Cambrian (early Boomerangian, cassis Zone). L. pearylandica described by Peel (1988) from the

Middle Cambrian Holm Dal Formation is similar to L. accordionata, but is more laterally compressed with finer, more numerous comarginal rugae. M a t e r i a l - 163 specimens from clasts W1, W2, W3, Wl0, W19, W38, W/L1/S1, W/L1/S4, W/L1/S5, W/L1/S6, W/L1/S7.

Latouchella accordionata RUNNEGAR• JELL, 1976

Latouchella aliciae nov. sp.

Fig. 3.4-6 1976Latouchella accordionata RUNNEGAR8: JELL, p. 127,

fig. 10C, 1-18; non 11. ? 1985 Latouchella sp. cf. L. accordionata RUNNEGAP8: JELL: MacKinnon, p. 68, figs 1M, P-R 1 9 9 0 L a t o u c h e l l a ct: accordionata RUNNF(;A~t & JELL: Kruse, p. 48, pl. 23A-M 1 9 9 1 L a t o u c h e l l a cf. accordionata RU~,'NE(~A~ 8: JELL: t~'use, p. 181-182, figs 9A-F

- Tall, moderately cyrtoconic univalves with prominent, regularly spaced, angular comarginal rugae. Fine radial threads present; aperture subrectangular to subcircular, tapering toward sub-apical apertural margin (from Runnegar & Jell 1976, p. 127). Diagnosis

- Moderately high, cyrtoconic, univalves (length usually between 2-5 ram, measured from apertural plane to highest point of coiling) with simple, regularly spaced, angular comarginal rugae and up to one, loosely coiled, whorl. Fine radial ornament preserved on some specimens. Aperture dominantly subcircular, occasionally subrectangular, with prominent posterior taper. Inner surface of sub-apical shell wall with a pair of uniformly thin ridges. Description

- The specimens from the Murrawong Creek Formation are conspecific with L. aecordio-

Discussion

Fig. 3.7-12; 4.1-3 1976 Latouchella accordionata RUNNEGAR8: JELL, fig. 10C, 11 only.

- Moderately involute, cyrtoconic, robust Latouchella with well developed, sharply angular, coarse comarginal rugae split horizontally by a distinct median notch; relatively wide space between rugae, especially on supra-apical surface. Diagnosis

Description - Moderately involute, robust univalves with average length 6 mm, rare specimens up to 8 mm in length. Almost one complete loose whorl; comarginal rugae coarse, prominent and angular, the anterior median portion of each ruga split horizontally to form well developed notch. Each ruga separated by relatively wide interrugal space, especially on supra-apical surface. Fine, closely spaced, radial threads on external surface. Aperture planar, outline suboval to subrectangular. Inner subapical margin with pair of narrow ridges.

- L. aliciae approaches L. merino in the coarseness of the comarginal rugae, but the latter has tighter coiling, and does not develop "notched" rugae. L. accordionata can be distinguished from L. aliciae by its much more closely spaDiscussion

577 ced rugae, lacking a median notch (see Runnegar and Jell 1976, fig. 10C, 1-10, 12-18). The shell of L. accordionata also tends to be slightly taller (Fig. 3.1-3) and less coiled than L. aliciae (Fig. 3.4,7; 4.1-3). One specimen referred to L. accordionata by Runnegar & Jell (1976, figs 10C, 11) has distinct development of median notches on co-marginal rugae and, unlike the closely packed rugae characteristic of L. accordionata, the rugae are spaced at much wider intervals indicating an affinity with L. aliciae. This specimen (which lacks a m u s e u m number) comes from the early Middle Cambrian "first discovery limestone" in western N.S.W. L. iacobinica described by Geyer (1986, p. 77-78, pl. 3, figs 29-30) from the Middle Cambrian of Morocco has a similar rate of coil, and some anterior comarginal rugae display faint "notches" (Geyer 1986, pl. 3, fig. 30), but this species can be discriminated by the presence of concentric lirae. L. arguta (REssEa, 1939) described by Geyer (1994) from the Middle C a m b r i a n Langston Formation, Idaho, has a similar rate of coil to L. aliciae, b u t can be distinguished by having much broader and rounded comarginal rugae, and the presence of concentric threads. L. holrndalense from the Middle Cambrian Holm Dal Formation, North Greenland (Peel 1988, p. 152, figs 7A-H, 8) and L. costata, the type species, from the Lower Cambrian of Shropshire (Cobbold 1921, p. 366, pl. 24, figs 41-42) can both be distinguished from L. aliciae by having fewer, more rounded and closely spaced comarginal rugae. E t y m o l o g y - In honour of my daughter, Alicia. M a t e r i a l - 182 specimens from clasts W1, W3, wg, W19, W38, W/L1/S1, W/L1/S4, W/L1/S5, W/L1/S6, W/L1/S7, W/L1/S8.

Family YOCHELCIONELLIDAERunnegar & Jell, 1976 Genus Y o c h e l e i o n e l l a RUNNEGAR& POJETA, 1974 T y p e s p e c i e s - YochelcioneUa cyrano RUNN~C~Aa & POJL~;'I'A, 1974.

D i s c u s s i o n - These small univalves are characterised by the "development of a tube-like extension of the sub-apical wall of the calcareous shell" (Berg-Madsen & Peel 1987, p. 259) termed a "snorkel" by Runnegar & Jell (1976). Pojeta & Runnegar (1976) and Runnegar & Jell (1976) interpreted the shell of Yochelcionella to be exogastric with the apex directed anteriorly over the head of the animal, the "snorkel" acting as the conduit for the inhalant stream into the mantle cavity; the exhalant waters being voided posterolaterally. A number of authors including, Yochelson (1978), Geyer (1986) and Peel & Yochelson

(1987) challenged this interpretation, favouring an endogastrically coiled shell with the "snorkel" directed posteriorly, with oxygen-rich inhalant currents entering the mantle cavity postero-laterally and flushing the posteriorly situated respiratory organs; deoxygenated waters being expelled through the "snorkel" (Peel 1991a). Riedel (1996), in discounting the latter scenario, has speculated that Yochelcionella was exogastric and the snorkel m a y have been used as a conduit for inhalant and exhalant currents, and that the gills were possibly reduced and oxygen taken up via the mantle. Yochelcionella, originally described from the early Middle C a m b r i a n of A u s t r a l i a ( R u n n e g a r & Pojeta 1974), has now been recovered from LowerUpper Cambrian sequences in Russia (Missarzhevsky & Mambetov 1981), Greenland (Peel 1980), Denmark (Berg-Madsen & Peel 1987), Spain and Morocco (Geyer 1986), China (Pei 1985), and North America (Runnegar & Pojeta 1980; Peel 1987; Voronova et al. 1987). Additional reports of the genus in Australia have been provided by Runnegar & Jell (1976) and Runnegar in Bengtson et al. (1990). Yochelcionella daleki RUNNECAR& JELL, 1976 Fig. 4.4-10 1976 Yochelcionella daleki RUNNECA~ & JELL, p. 130, figs l l A , 11-19. 1978 Yochelcionella daleki RUNNEGA~ & JELL; Jell, illustrations d, e.

D i a g n o s i s - Tall, endogastric univalves with a long slender siphon; ornament consists of closely spaced comarginal plicae and fine radial threads that converge to form a star-shaped pattern at the apex (modified after Runnegar & Jell 1976, p. 13o). D e s c r i p t i o n - Tall, weakly cyrtoconic univalves with regularly and closely spaced, thin concentric plicae. Apical region without comarginal plicae, smooth or with fine radial lirae. Siphon opening ovoid, relatively large (0.4 mm), posteriorly to postero-dorsally directed. Apertural rim planar; ovoid in outline. D i s c u s s i o n - None of the specimens recovered from the Murrawong Creek Formation have a complete siphon preserved, however the opening in the subapical shell wall is clearly the attachment point for the siphon. The well developed, regular plicae and position of the base of the siphon indicate conspecificity with Y. daleki (see Runnegar & Jell 1976, p. 130, figs l l A , 11-19). One specimen does have a more postero-dorsally directed siphon (Fig. 4.8,9) similar to Y. ostentata, but the ornament is clearly that of an adult Y.

578 daleki (compare with specimen illustrated by Runnegar & Jell 1976, figs 11A, 15-16). The star shaped pattern at the apex of Y. daleki, fbrmed by the junction of fine radial threads, is not apparent in the Murrawong Creek specimens. This is likely to be preservational, but since the same pattern is also found in Y. ostentata the feature is of little taxonomic importance. Y. cyrano, the type species, is larger and more robust than Y. daleki. Y. americana can be discriminated by its more laterally compressed shell (see Runnegar & Pojeta 1980; Peel 1987). Y. stylifera is more laterally compressed and has wider, more prominent, but fewer, concentric plicae (Missarzhevsky & Mambetov 1981, pl. 15, figs 10-11). M a t e r i a l - 21 specimens from clasts W38, W/L1/S4, W/L1/S5.

Family STENOTHECIDAE Runnegar & Jell, 1980 Genus A n a b a r e l l a VOSTOKOVA,1962 T y p e s p e c i e s - Anabarella plana VOSTOKOVA,1962

D i s c u s s i o n - Anabarella can be distinguished from other laterally compressed univalves such as Mellopegma, Eurekapegma and Stenotheca by "the more prominent development and greater end curvature of the apex which in most specimens overhangs the anterior (= posterior in current interpretation) valve extremity" (MacKinnon 1985, p. 69). Eurekapegma is further discriminated by the presence of a zygion. Laterally compressed genera such as Anabarella are considered by some authors to have been semiinfaunal organisms (Runnegar 1983; MacKinnon 1985; Geyer 1994), but there seems to be little foundation for such a view. MacKinnon's (1985, Fig. 6B) reconstruction of Anabarella places the curved apex and flared apertural edge at the anterior of the animal. Peel & Yochelson (1987, p. 271) have interpreted the flared aperture in some specimens of Anabarella illustrated by Runnegar (1983, fig. 4A) and Runnegar & Pojeta (1985) as the remains of a "prominent ridge-like extension" associated, in life, with the development of a exhalant siphon similar to Oelandia. Though the presence of an exhalant siphon cannot be confirmed

by the specimen recovered from the Murrawong Creek Formation, it seems reasonable to assume that the apertural flare in Anabarella was associated with the voiding of metabolic and respiratory wastes. As such, Anabarella, like most other helcionelloids, probably had an untorted, endogastric shell with the apex directed towards the posterior of the animal. Anabarella simesi MACKINNON, 1985 Fig. 4.11-13 1985 Anabarella simesi MACKINNON, p. 71, figs 3A-J.

E m e n d e d d i a g n o s i s - Shell coiled up to one half a whorl; aperture elongate oval, broadest posteriorly, maximum constriction posterior of midline; aperture dorsally expanded at posterior end; subdued, comarginal growth banding retained on internal moulds (modified after MacKinnon 1985, p. 71).

Description - Single, small, cyrtoconic, highly compressed steinkern with approximately half a whorl and with weakly expressed, wide, posteriorly tapering comarginal rugae. Shell dimensions 1.5 mm in length x 0.6 mm high. Apertural outline e]ongate]y oval, widest anteriorly (0.25 mm anterior apertural width), medially constricted and tapering posteriorly (0.I mm posterior apertural width). Posterior apertura] edge flared dorsally towards overhanging, curved apex. Discussion - The single specimen recovered displays the same degree of lateral compression, shell coiling, weak comarginal rugae and apertura] outline (Fig. 4.1-3) as the specimens originally described by MacKinnon (1985, fig. 3A-J) from the Middle Cambrian Tasman Formation in New Zealand. In following current interpretations favouring a posterior orientation for the apex, the anterior and posterior descriptions given by MacKinnon (1985) are reversed here, and the species diagnosis is emended accordingly. The Lower Cambrian species A. australis from the Parara Limestone, Horse Gully, South Australia (Runnegar in Bengtson et al. 1990, p. 244, 251, figs 163A, 164A-G) is more cyrtoconic with wider coiling, and a greater posterior apertural flare. As

FIGURE 4 - 1-3. Latouchella aliciae nov. sp. 1, lateral view, with well defined "notched" comarginal rugae, AMF97391, from clast W/L1/S4, [x 20]. 2, lateral view of AMF97393, from clast W/L1/S4, [x 16]. 3, oblique lateral view of AMF97392, from cIast W/L1/S4, [x 20]. 4-10. Yochelcionella daleki RUNNEC~A~& JELL. 4-5, lateral and apertural view of AMF97396, from clast W38, [x 37]. 6-7, oblique lateral and oblique apertural views of AMF97397, from clast W38, [x 35]. 8-9, lateral and dorsal views of AMF97398, from clast W/L1/S4, [x 30]. 10, lateral view of AMF97381 from clast W/L1/S4, [x 25]. 11-13. Anabarella simesi MAcKINNON, oblique apertural view [x 41], lateral view [x 40], and close-up of posterior apertural rim [x 170] of AMF97399, from clast W10.1-3. Latouchella aliciae nov. sp. 1, vue latdrale, avec des rugae comarginales "denteldes" bien dessindes, AMF97391, du claste W / L 1 / $ 4 , Ix 20]. 2, rue latdrale de AMF97393, du claste W / L 1 / S 4 , Ix 167. 3, rue latdrale oblique de AMF97392, du claste W / L 1 / S 4 , Ix 20]. 4-10. Yochelcionella daleki RUNNEC,AR & JELL. 4-5, rues latdrales et eperturales de AMF97397, du claste W38, Ix 37]. 6-7, rues latdrales obliques et aperturales obliques de AMF97397, du claste W38, [x 35]. 8-9, vues latdrales et dorsales de AMF97398, du claste W / L 1 / $ 4 , Ix 30]. 10, vue latdrale de AMF97381 du claste W / L 1 / $ 4 , Ix 25]. 11-13. Anabarella simesi MAcK~NNON, rue aperturale oblique [x 41], vue latdrale [x 40] et gros plan du bord postdrieur apertural Ix 170] de AMF97399, du claste WIO.

579

580 noted by MacKinnon (1985, p. 71) the Tommotian species A. plana Vostokova is larger and more involute (with one complete whorl) than A. simesi. A. indecora Missarzhevsky from the Tommotian of the Siberian Platform has less apical curvature and more prominent comarginal rugae. M a t e r i a l - 1 s p e c i m e n from W l 0 .

Class ?GASTROPODACuvier, 1797 Order ?ARCHAEOGASTROPODAThiele, 1925 Superfamily BELLEROPHONTOIDEAM'Coy, 1851 Family and Subfamily Unknown Genus P r o t o w e n e l l a RUNNEGAR& JELL, 1976 Type species -

Protowenella flemingi

RUNNEGAR gg JELL, 1976

- Protowenella has variously been reconstructed as an untorted exogastrically coiled monoplacophoran (Runnegar & Jell 1976; BergMadsen & Peel 1978; Missarzhevsky 1989), an untorted endogastrically coiled helcionelloid (Peel 1988, 1991a,b) or a torted endogastrically coiled gastropod (Riedel 1996). Such disparate interpretations of the systematic placement of this genus has essentially been controlled by three factors: 1. the fact that all known specimens are steinkerns lacking details of muscle scars, shell ornament etc., 2. the functional interpretation and significance of circumbilical channels, and 3. the broader question of the affinities of early Palaeozoic bellerophontiform univalves. Discussion

Specimens of Protowenella are invariably preserved as phosphatic or limonitic steinkerns, and apart from the presence of faint transverse ornament on a single steinkern from the Middle Cambrian of Bornholm (Berg-Madsen & Peel 1978, fig. 6E; Peel 1991a, fig. 15B) nothing is known about the ornament, shell composition (though the shell is assumed to have been relatively thin and composed of calcium carbonate), or the position, shape, and number of muscle scars. As a result, the affinities of Protowenella have been deduced almost entirely on t h e planispiral shell shape, and functional interpretation of circumbilical channels on the umbilico-lateral margins of this taxon. Berg-Madsen & Peel (1978, p. 119) stressed the importance of the latter features in Protowenella by including them in their emended diagnosis of the genus. Berg-Madsen & Peel (1978, p. 120) originally suggested the circumbilical channels in Protowenella could be interpreted as the sites for inhalant water currents entering the mantle cavity, and that the genus was probably an exogastrically coiled, untorted tergomyan. Berg-Madsen & Peel (1978) tentatively retained Protowenella within the Multifariidae (sensu Runnegar & Jell 1976)

based on the similarity of shell coiling with Multifariites, but noted that lack of muscle scars in Protowenella hindered detailed comparison. Peel (1988, 1991a, b) subsequently modified the interpretation of Berg-Madsen & Peel (1978), in line with his functional reinterpretations of other helcionelloids, such as Yochelcionella, Latouchella and Oelandia (Peel & Yochelson 1987), and suggested that Protowenella was an endogastrically coiled helcionelloid with the apex oriented posteriorly, and exhalant w a t e r currents emerged below the sub-apical margin of the shell. In this interpretation, Peel (1991b) considered the circumbilical channels of Protowenella to be homologous with the raised ridges on the inner sub-apical shell margin of Latouchella. This functional reinterpretation of Protowenella led to a re-valuation of the taxonomic placement of the genus, and Peel (1991a, b) transferred the genus to the newly erected Class Helcionelloida. Riedel (1996, p. 123-124) provided new impetus to the debate over the affinities of Protowenella, by interpreting the umbilical channels in Protowenella as pseudosutures formed by the deformation of the nonmineralised larval shell during torsion. Such pseudosutures, according to Riedel (1996, p. 124) reflect "torsion objectively", and indicated Protowenella was a true gastropod. Evaluation of the scant morphological evidence currently known, indicates that Protowenella m a y have an affinity with the gastropods or possibly the tergomyans, but is unlikely to be related to the helcionelloids. The circumbilical channels in Protowenella are similar to those reported in a number of planispiral tergomyans such as Sinuitopsis (STAROBOGATOV,1970), Pharetrolites (PEEL, 1975), Retipilina, and Undicornu (HORN~, 1970), as well as some planispiral bellerophontid gastropods such as Sinuites (see HornSr 1991a, p. 95). Importantly, Horn:~ (1991b, p. 95) interprets the circumbilical channels in tergomyans as tentacular sinuses, and not as inhalent channels. Peel's (1991b) contention that the circumbilical channels are homologous to ridges in Latouchella is not supported here. Riedel (1996), of course, would simply envisage all these planispiral taxa (especially those with umbilical channels) as gastropods. The fact that umbilical channels similar to those found in Protowenella are also known in molluscs with ultradextral coiling (generally accepted as gastropods) such as Xinjispira simplex (Z~ou & XIAO) illustrated by Yu (1987, pl. 68, fig. 5) from the Lower Cambrian Xinji Formation, Henan, China supports the link between Protowenella and the Gastropoda.

581

While acknowledging the argument that it may be virtually impossible to distinguish planispiral gastropods from untorted tergomyans on the basis of muscle scars alone (Harper & Rollins 1982; Peel 1980, p. 96; Wahlman 1992, p. O55), the discovery of a large, raised crescentic scar on the right umbilical shoulder of a single specimen, assigned herein to Protowenella, from the Murrawong Creek Formation, m a y prove, nonetheless, to be significant in the debate over the affinities of Protowenella. The a r c u a t e scar, though proportionally larger than in other bellerophontiform taxa, conforms to the expected position and area of raised relief characteristic of muscle scars in bellerophontiform molluscs such as Bellerophon, Sinuites and Strangulites (Knight 1947; Peel 1972; Berg-Madsen & Peel 1978; Peel 1991b), which are considered by most (but not all) workers to be isostrophically coiled, torted gastropods. The position of the scar, deep inside the conch, on the umbilical shoulder is strongly suggestive that the animal was capable of retracting into the shell, an ability clearly found in gastropods and possibly some tergomyans (Peel 1980; Wahlman, 1992). Despite obvious similarities between Protowenella and exogastric tergomyan taxa, such as Sinuitopsis PERNER,Pharetrolites PELL and Telamocornu BERG-MADSEN& PEEL, the position of the muscle scar in Protowenella sp. is certainly different from that found in typical tergomyans such as Cyrtonella and Sinuitopsis, which are characterised by a series of paired scars distributed around the whorl. For the same reason it is t h u s difficult to continue to view Protowenella as closely related to Multifariites BYALI, 1973, which has multiple paired muscle scars on the inner dorsal shell surface (see Wingstrand 1985, fig. 19). The assignment of Protowenella to Multifariidae, as advocated by Runnegar & Jell (1976) and Berg-Madsen & Peel (1978) is thus considered unlikely. Though it seems reasonable to interpret the scar preserved in the Murrawong Creek Formation specimen as homologous to a bellerophontid scar based on the general position and shape of the scar, I prefer to take a more cautionary approach fbr the following reasons: 1. the preserved scar has thus far only been found in one individual, and though such fortuitous preservation is not unknown in the fossil record (e.g. muscle scars in a single specimen of Pelagiella atlantoides described by Runnegar 1981), more material is needed to confirm the validity of the muscle scar interpretation, 2. the scar is preserved on only one side of the specimens despite no apparent preservational difference in the steinkern (Fig. 5.3-4), and this must be reconciled with the paired scars typically found in bellerophontids, 3. similar types of scars (spiral ribs) have

been recorded in the primary shells of some Triassic to Recent conchiferan molluscs (see Bandel 1982, pl. 3, fig. 7; pl. 5, figs 4-5, pl. 6, fig. 12), but these are generally considerably smaller than Protowenella conchs, and 4. the broader question of bellerophontiform affinities has not yet been clarified. Some authors, such as Pojeta & Runnegar (1976), Runnegar & Jell (1976) and Runnegar (1996) interpret all planispiral univalves as untorted monoplacophorans, others such as Harper & Rollins (1982) and Riedel (1996) favour recognising all bellerophontiform univalves as torted, endogastically coiled gastropods. Other workers, recognising the inherent dangers in attaching undue significance to muscle scar patterns in morphologically disparate forms, consider the bellerophontids to be a mixture of untorted tergomyans and torted gastropods (Peel 1991a,b; Wahlman 1992). Runnegar (1996, p. 81) has suggested that the bellerophontids sensu lato "fall between the Tergomya and the Gastropoda with the origin of torsion separating the two groups". Given the uncertainty concerning the higher level affinities of the bellerophontids, I have tentatively aligned Protowenella with the Archaeogastropoda, based primarily on the similarity of shell coiling, the shape and position of the muscle scar in Protowenella with post-Cambrian bellerophontids, and the presence of circumbilical channels in ultradextrally coiled shells. Hinz (1987, p. 55) has also reported, but not illustrated, a specimen of a questionable Protowenella from the Early Cambrian Lower Comley Limestone with a "typical apertural slit" similar to many post-Cambrian bellerophontids. Under current gastropod classification (see for e.g. Wahlman 1992, table 17), the morphology of Protowenella does not conform adequately with any of the currently recognised families or subfamilies, a fact already noted by Missarzhevsky (1989). Given the limited morphological information on Protowenella, the family and subfamily designations are left open at present.

Perssuakiella Peel from the late Middle Cambrian Holm Dal Formation, central north Greenland, has a similar globose planispiral shell with almost one whorl, but can be distinguished from Protowenella by the presence (in late growth stages) of a distinct marginal brim and the lack of umbilical channels. The small planispiral genus Kutanjia KaUSE from the early Middle Cambrian (Ordian) Top Springs Limestone, n o r t h e r n Georgina Basin, Northern Territory is distinguished by interior rib-like co-marginal thickenings and weak radial ornament (Kruse 1991).

Protowenella was originally described by Runnegar & Jell (1976) from the Currant Bush Limestone (Floran-Undillan stages, P. atavus-E, opimus

582 zones) in the Georgina Basin, and a single specimen was recovered from the early Middle Cambrian (Ordian) "first discovery limestone" of the Coonigan Formation, western N.S.W. It has now b e e n recovered from broadly coeval strata in D e n m a r k (Berg-Madsen & Peel 1978; Peel 1991a), Greenland (Peel 1979), late Middle Cambrian strata in New Zealand (MacKinnon 1985) and the early Middle Cambrian of Morocco (Geyer 1986). Missarzhevsky & Mambetov (1981) have also d o c u m e n t e d Protowenella from the Lower Cambrian of Maly K a r a t a u and Missarzhevsky (1989) has reported the same species from Lower C a m b r i a n (Botomian) s t r a t a of the Siberian Platform. Hinz (1987) also noted the genus f~om Lower Cambrian strata at Comley, England.

Protowenella sp. Fig. 5.1-4 D e s c r i p t i o n - Small, globose, planispiral steink e r n with one full, relatively tight, whorl. Umbilical channels not preserved (or lacking?). Right umbilical shoulder with large arcuate, crescentic, slightly raised scar, possibly representing site of muscle attachment. Apertural outline subcircular. D i s c u s s i o n - The large crescentic structure preserved on the right umbilical shoulder of the specimen (Fig. 5.3-4) is tentatively interpreted as the site of muscle attachment similar to that described in some bellerophontiform molluscs by Knight (1947) and Peel (1972, 1991b). The presence of the slightly raised relief of the preserved scar on the Murrawong Creek Formation specimen conforms to the expected style of preservation for a muscle a t t a c h m e n t scar in a steinkern of Protowenella as outlined by Berg-Madsen & Peel (1978, p. 120). The width of the scar appears to be greater than in Bellerophon (see Peel 1972, textfig. 2B, pl. 79, figs 1, 2), but occurs in the same approximate position. This type of muscle scar has not previously been noted in steinkerns of Protowenella. While it is acknowledged that "Protowenella-like morphologies might result from preservation of the early growth stages of different helcionelloids" (Peel 1991a, p. 168), the size, degree of coiling and apertural shape of Protowenella sp. from the Murrawong Creek Formation, appears to be typical of the genus.

Protowenella sp. from the Murrawong Creek Formation is similar to P. cobbensis described by MacKinnon (1985) from the late Middle Cambrian Tasman Formation, New Zealand, in that it lacks the circumbilical channels diagnostic of the genus and the type species, P. flemingi (BergMadsen & Peel 1978, fig 6A-D). The steinkerns from the Murrawong Creek Formation are also

similar to P. cobbensis in having no trace of external ornament preserved, whereas Berg-Madsen & Peel (1978, fig 6E) show a steinkern ofP. flemingi with traces of transverse ornament. However, Protowenella sp. can be discriminated from the otherwise morphologically similar P. cobbensis, by its more circular apertural outline and slightly tighter and more uniform whorl. The fact that both taxa lack circumbilical channels diagnostic of the genus sensu Berg-Madsen & Peel (1978) raises some taxonomic problems. If the emended generic concept of ProtowenelIa sensu Berg-Madsen & Peel (1978) is accepted, then P. cobbensis and Protowenella sp. (and most other identified species) cannot strictly be included in the genus. The lack of circumbilical channels is more reminiscent of the Middle Cambrian taxon Perssuakiella troelseni PEEL from Greenland (Peel 1988); however P. troelseni, known from one complete specimen, is less involute than P. cobbensis and Protowenella sp. P. troelseni also possesses a distinct marginal brim, not known in P. cobbensis or Protowenella sp., though ~his leature is not likely to have been preserved in steinkerns. Runnegar (in Bengtson et al. 1990, p. 251, fig. 162I, J) has suggested that smooth forms of univalves he described as Propilina, interpreted as a tryblidacean, from the Early Cambrian of South Australia "may be allied to Protowenella cobbensis (MAcKINNON, 1985)". However, the lack of serial muscle scars in P. cobbensis and the presence of a single large scar in Protowenella sp. argues against a tryblidid affinity (see also Geyer 1994). Alternatively, if the lack of circumbilical channels is merely preservational, then there is little to separate P. cobbensis from the type species, and this species could thus be regarded as a junior subjective synonym of the type. Given that the shell size, apertural outline and degree of coiling in P. cobbensis and Protowenella sp. is similar to the type species, an affinity with Protowenella seems likely. The validity of P. cobbensis can only be tentatively accepted based on MacKinnon's (1985, p. 75) observation that P. cobbensis has a "gTeater rate of whorl expansion" than P. ]qemingi and that there is no evidence of ornament on P. cobbensis. The specimen described by Runnegar & Jell (1976, fig 6A) as Protowenella sp. apparently differs from P. flemingi and P. cobbensis in being less volute and having a rounded aperture. Unfortunately, only an apertural view of the specimen was illustrated by Runnegar & Jell (1976, fig 6A) making closer comparison impossible; no mention was made of circumbilical scars. The specimens illustrated and described as Protowenella sp. from

583

FIGURE 5 - 1-4. Protowenella sp., AMF97386, from clast W38.1, right oblique lateral view of steinkern lacking umbilical channel or muscle scar, Ix 90]; 2, apertural view of steinkern, Ix 90]; 3, left lateral view of steinkern with slightly raised, crescentic muscle scar on umbilical shoulder, [x 90]; 4, close-up of muscle scar, [x 250]. 5-7. Pelagiella sp. cf. P. deltoides RUNNEGAR& JELL from clast W1.5-6, lateral and apertural views of AMF97400, [x 70]. 7, lateral view of AMF97401, from clast W1, [x 70]. 1-4. Protowenella sp., AMF97386, du claste W38. 1, rue droite lat~rale oblique du steinkern sans tube ombilical ou impression musculaire, Ix 90]; 2, vue aperturale du steinkern, [x 90]; 3, vue gauche lat~rale du steinkern avec impression musculaire en forme de croissant et l~g~rement en relief sur l'~paule ombilicale, Ix 90]. 4, gros plan de l'impression musculaire, Ix 250]. 5-7. Pelagiella sp. cf P. delto~des RUNNE¢A~ & J~LL du claste W1. 5-6, vues latgrale et aperturale de AMF97400, [x 70]. 7, vue latgrale de AMF97401, du claste W1, [x 70].

t h e e a r l y Middle C a m b r i a n of Morocco b y G e y e r (1986, pl, 3, figs 48-49) also a p p e a r to lack circ u m b i l i c a l c h a n n e l s , t h o u g h G e y e r (pers. comm.) h a s i n d i c a t e d c i r c u m b i l i c a l c h a n n e l s are a c t u a l l y p r e s e n t in t h e M o r o c c a n m a t e r i a l . P. p l e n a report e d b y M i s s a r z h e v s k y (1989) f r o m t h e B o t o m i a n of t h e S i b e r i a n P l a t f o r m a n d t h e L o w e r C a m b r i a n of M a l y K a r a t a u ( M i s s a r z h e v s k y & M a m b e t o v 1981) l a c k s a n u m b i l i c a l channel, b u t is larger, more transverse and has a circular aperture. Material - 3 specimens from clast W38, 1 fragmentary specimen from clast Wl. C l a s s PARAGASTROPODA L i n s l e y & Kier, 1984 O r d e r PELAGIELLIDA M a c K i n n o n , 1985 F a m i l y PELAGIELLIDAE Knight, 1956

Genus

Pelagiella MATTHEW,1895

Type species - Cyrtolithes atlantoides MATTHEW1894. , D i s c u s s i o n - M a t t h e w (1894) o r i g i n a l l y describ e d P e l a g i e l l a as a n e w g e n u s of b e l l e r o p h o n t i d g a s t r o p o d , b u t r e c o n s i d e r e d t h i s v i e w one y e a r l a t e r ( M a t t h e w 1895), r e c o g n i s i n g t h e a s y m m e t r y of form. H e i n t e r p r e t e d t h e g e n u s as a f r e e s w i m m i n g f o r m r e l a t e d to t h e h e t e r o p o d s . K n i g h t (1941) d e s i g n a t e d t h e h o l o t y p e f r o m M a t t h e w ' s original collection a n d classified t h e g e n u s as a g r o u p of a n o m p h a l o u s g a s t r o p o d s . Y o c h e l s o n (1975, p. 661) n o t e d t h a t "pelagiellids do n o t look particularly gastropod-like" and advocated they be v i e w e d as Mollusca i n c e r t a e sedis. L i n s l e y & K i e r (1984) i n d i c a t e d pelagiellids w e r e d e x t r a l ,

584 orthostrophic, u n t o r t e d univalves, and assigned t h e g r o u p to t h e s u p e r f a m i l y P e l a g i e l l o i d e a K n i g h t 1956, in t h e i r n e w Class P a r a g a s t r o p o d a a n d O r d e r O r t h o s t r o p h i n a . The class P a r a g a s t r o p o d a n e a t l y g a t h e r s t o g e t h e r a n u m b e r of u n u sual e a r l y Palaeozoic a n i s o s t r o p h i c u n i v a l v e s t h a t c a n n o t easily be a s s i g n e d to t h e G a s t r o p o d a , Helcionellida or T e r g o m y a . B a s e d on t h e p r e s e r v a t i o n of muscle scars in a s p e c i m e n of P. atlantoides from a slightly y o u n g e r h o r i z o n t h a n t h e t y p e locality, R u n n e g a r (1981, p. 317) i n t e r p r e t e d Pelagiella as "a m o n o p l a c o p h o r a n w h i c h h a s u n d e r g o n e a b o u t 10 ° of torsion." M a c K i n n o n (1985, p. 75), in recognition of R u n n e gar's (1981) concept of t h e group, erected the O r d e r Pelagiellida for a g r o u p of "helically coiled u n i v a l v e s w i t h a r e l a t i v e l y low, flat spiral side a n d a swollen umbilical side; a p e r t u r e oval to sub t r i a n g u l a r in shape". M a c K i n n o n (1985) is gener a l l y r e c o g n i s e d as t h e a u t h o r of the O r d e r Pelagiellida, as his p a p e r h a s slight chronologic p r e c e d e n c e over R u n n e g a r & Pojeta's (1985) erection of t h e O r d e r Pelagiellida.

Pelagiella sp. cf. P. deltoides RUNNEGAR& JELL, 1976 Fig. 5.5-7 - All specimens are preserved as coarse steinkerns, lacking a n y f r a g m e n t of original shell material. The shells have a distinctly subt r i a n g u l a r a p e r t u r a l outline and a similar degree o f v o l u t i o n to the s t e i n k e r n s ofP. deltoides fl~om the C u r r a n t B u s h Limestone, Georgina Basin, described by R u n n e g a r & Jell (1976, fig. 7A-I). Discussion

Material

-

17 specimens from clasts W1, W10, W/L1/S4,

W/L1/S7. Acknowledgements - This is a contribution towards ARC project A39331590 to J.A. Talent et al. on the Devonian and preDevonian of the Tamworth Belt. J.S. Peel (Uppsala University), I. Percival (Geol. Survey N.S.W.), I. Stewart (Monash University), J.A. Talent, T.R. Sloan and M. Engelbretsen (all MUCEP) answered queries, provided copies of pivotal literature, and participated in thoughtful discussions of the fauna. An earlier draft of this ms. was improved by comments and suggestions by A. Simpson (Univ. of Qld.) and Ian Percival. D. Mathieson (MUCEP) helped with photographic printing. J.A. Talent and R. Mawson (MUCEP) provided endless encouragement and friendship and, importantly the necessary logistical support to finish the project. Gerd Geyer (W~rzburg) reviewed the manuscript and made valuable improvements. Partial funding for this work was provided by a grant from the Joyce Vickery Scientific Research Fund of the Linnean Society of N.S.W.

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Centre for Ecostratigraphy and Palaeobiology School of Earth Sciences Macquarie University N.S.W. 2109, Australia

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