https://doi.org/10.24199/j.mmv.1978.39.02 7 July 1978 GASTROPODS FROM THE EARLY DEVONIAN BELL POINT LIMESTONE, CAPE LIPTRAP PENINSULA, VICTORIA By C. B. Tassell Albany Residency Museum, Albany, Western Australia Abstract One new genus and five new species of gastropods are described from the late Early Devonian Bell Point Limestone, on Cape Liptrap Peninsula, 150 km south-east of Melbourne. Six other gastropod taxa are recorded. The new genus Bassotrochus is assigned to the family Omphalotrochidae. Together with Orecopia murrayi sp. nov., also from the Bell Point Lime- stone, Bassotrochus angulatus sp. nov. represents the earliest known occurrence of this family to date. The other species are Tropidodiscus waratahensis sp. nov., Straparollus (Euomphalus) sp., ? Mourlonia sp., Gyronema bellense sp. nov., Murchisonia (Murchisonia) bassensis sp. nov., M. (Murchisonia) sp. A, M. (Murchisonia) sp. B and M. (Hormotomina) sp. Also described are Micromphalus clarkei (de Koninck) from near Yass, N.S.W. and an indeterminate form from the Waratah Limestone, Cape Liptrap Peninsula. This shallow water gastropod fauna occurs as both coquinite and non-coquinite assem- blages associated with a diverse invertebrate community which includes corals, stromatopor- oids, bivalves and brachiopods. Introduction pods have only been mentioned in passing un- The Bell Point Limestone occurs as a small til now. Lindner (1953, p. 82) noted 'a trocho- faulted block on the eastern side of Cape Lip- form gastropod is the only fossil in the lowest trap Peninsula which is approximately 150 km 75 feet'. Above this spiriferid brachiopods oc- south-east of Melbourne. Exposed on this cur together with the gastropod. Higher in the peninsula are sections of the Waratah Bay section 'several small species of gastropods, in- axis, one of a number of such structural axes cluding turreted and turbinate forms' occur. occurring in Victoria. This axis has been the Similarly, Teichert (1954) listed gastropods site of considerable tectonic activity and as a amongst the abundant fauna of the Bell Point consequence some major faults occur on the Limestone at Bell Point. eastern side of the peninsula. Besides the Bell Talent (as cited by Singleton, 1968) listed Point Limestone, certain other units are also Bellerophon and Coelocaulus amongst the only exposed in a few small areas. These in- gastropods occurring in the Waratah Lime- clude the Early Devonian Waratah Limestone stone. The gastropods listed for the Bell Point and the Early Ordovician Digger Island Lime- Limestone include Tropidodiscus, Amphelissa stone, isisensis and 'a new Trochid'. The limestones at Cape Liptrap have been Bounded by faults and in close proximity known for some time, Ulrich (1875) being to the large Waratah fault, the Bell Point Lime- the first to mention them in print. However, it stone has been subjected to some stress. Partly was not until recently that the stratigraphy of as a result of this many of the gastropods are the area has become adequately known. The distorted, in addition to the crushing and most recent account of the geology being that fragmenting of the shells associated with the of Singleton (1968). initial compaction of the sediment. McCoy (1877) described the first fossil As many of the specimens are either Palaeopora interstincta ( Wahl ) from the crushed, fragmented or distorted the measure- Waratah Bay area. In 1898 Etheridge noted a ments given can only be considered as a gene- dorsal valve of a spirifer, some crinoid frag- ral indication of the specimens' original shape. ments and a new coral Tryplasma. Since then All measurements are in millimetres and the some elements of the limestone fauna including following symbols relating to the measurements corals, ostracods and brachiopods have been have been used: c, number of spiral cords; described. Hap, height of aperture; Ht, total height of Although abundant at Bell Point, gastro- shell; L, length measured at the selenizone in 19 IQ C, B. TASSELL the bellerophontids, Wap, width of aperture; Point constitutes the earliest occurrence of Wh, total number of whorls in shell; Wt, total the family to date. Their presence and that of width of shell. Micromphalus clarki in the Late Silurian sedi- All specimens used in this study are lodged ments of the Yass Basin, indicate an affinity in the palaeontological collection of the Na- not previously suspected of the Australian gas- tional Museum of Victoria. tropod fauna with younger Devonian gastro- pod faunas of the Northern Hemisphere (Tas- Age of the Faunas sell, 1976). When Talent (1965) discussed the Bell Point Limestone he commented upon the simi- Palaeoecology larity of the brachiopod fauna to that in the The Bell Point Limestone is a well bedded Buchan Caves Limestone. Such a similarity is dark muddy limestone within which minor also found amongst some of the other faunal amounts of lighter grey limestone and black elements of the two limestones (Vandenberg shale occur. Lindner (1953) considered that it et at., 1976). Philip and Pedder (1967) recog- was at least 140 feet thick. Although there has nized their coral-conodont Fauna D in both been some disagreement about the depth of de- the Buchan Caves Limestone and the Taemas position of the Early Devonian sediments else- Limestone. This coral-conodont fauna is now where in the Melbourne Trough it is generally considered to be Early Emsian in age (Strusz, agreed that the carbonate sediments occurring 1972). on the Waratah Bay axis were deposited in In the older Waratah Limestone, Talent shallow water (Singleton, 1968; Vandenberg (1965) recognized a fauna containing many etal. 1976). elements which showed considerable similarity Part of the prolific and diverse fauna of the to that in found the Coopers Creek Formation. Bell Boint Limestone has been described in the The coral-conodont Fauna B of Philip and past (Hill, 1954; Krommelbein, 1954; Talent, Pedder which has been found in both the 1956; Pedder, 1965). The fauna includes Waratah Limestone and the Coopers Creek stromatoporoids, tabulate and rugose corals, Formation is now considered to be Late Sie- brachiopods, bivalves, rostroconchians, gastro- genianin age (Strusz, 1972). pods and ostracods. The faunas in this unit are As with previous studies of middle Palaeo- preserved in two ways, either as coquinite zoic gastropods in southeastern Australia, this assemblages or non-coquinite assemblages. Al- study makes little contribution toward age de- though less frequent the coquinite assemblages terminations of the limestones. Certainly Mur- are extremely prominent, for example, assem- chisonia (Murchisonia) sp. A from the Bell blages of Orecopia murrayi and Bassotrochus Point Limestone is very similar to Murchisonia angulatus thickly cover surfaces sometimes ex- (Murchisonia) turris de Koninck known to oc- ceeding 25 sq m in area. A characteristic of cur in the Emsian 'Receptaculites' Limestone these coquinite assemblages is their low faunal at Taemas, N.S.W. Similarly the indeterminate diversity. This is true for any such assemblage cyrtoconoid gastropod from the Waratah Lime- whether it is composed of gastropods, bivalves stone would appear to have an affinity with the or any other faunal component. Similar, al- poorly preserved Michelia sp. from the simi- most monospecific, coquinite assemblages have larly aged Toongabbie Limestone. been reported in Eastern North America (Mo- What is of considerable interest is the pre- Ghee, 1976). sence of the genera Orecopia, Bassotrochus Coquinas composed largely of O. murrayi and Straparollus (Euomphalus) in the gastro- are the most frequently occurring gastropod as- pod fauna. Both Orecopia and Bassotrochus semblages in the limestone. They consist of are members of the Omphalotrochidae, a fam- complete specimens of O. murrayi ranging in ily known principally from the Late Palaeo- diameter from 4 mm upwards, as well as zoic. The presence of these genera at Bell large quantities of angular shell fragments of BELL POINT LIMESTONE GASTEROPODA 21 the same species. Both the fragments and the Tropidodiscus waratahensis sp. nov. complete shells lack evidence of abrasion and (Plate 1, figure 1) transport. S. (Euomphalus) sp. and B. angula- Diagnosis: small form of genus with subdued tus also occur frequently in O. murrayi coquin- dorsal crest and fine closely spaced growth as. Similarly O. murrayi occurs in some of the lines. coquinas composed of B. angulatus or the pre- Description: Small form with angular dorsal sently undescribed bivalves. crest; whorl profile gently rounded between In contrast to the spectacular coquinas of dorsal crest and edge of the umbilicus, then 0. murrayi and B. angulatus the coquinas or rounds more strongly into the umbilicus; um- Tropidodiscus bedding plane concentrations of bilici deep and wide; aperture sub-triangular waratahensis are quite restricted, rarely ex- with a ridge formed by the dorsal crest of pre- ceeding a sq m in area. Unlike O. murrayi ceding whorl on the inner lip; inner lip thin; which occurs in association with bivalves in thick strongly prosocyrt outer lip passes back- some coquinas, those of T. waratahensis contain wards obliquely from the suture to form a numerous brachiopods. Again, evidence of moderately deep v-shaped sinus at the dorsal transport or abrasion is lacking. crest, narrow convex selenizone raised above possess a The non-coquinite assemblages former edges of the slit; fine closely spaced col- much greater faunal diversity. For example M. labral lines. (Murchisonia) bassensis occurs in the light grey limestone with rugose corals, bivalves, bra- Dimensions: chiopods, rostroconchians as well as occasional L Wh— individuals of O. murrayi. M. (Murchisonia) P46963 75 P46964 3 2 sp. B found in a similar limestone is associated P46965 4 3 + rugose corals, ostracods, bivalves, bra- with P46966 7 3+ chiopods, rostroconchians and infrequent ex- P46967 8 — amples of T. waratahensis. of Vic- The composition of this gastropod fauna Location of Types: National Museum E. D. Gill Coll. differs considerably from any other non-platy- toria. Holotype, P46963.