Austrohinnites Beu & Darragh, 2001
BEU, A. G. & T. A. DARRAGH. 2001. Revision of southern Australian Cenozoic fossil Pectinidae (Mollusca: Bivalvia). Proceedings of the Royal Society of Victoria, 113: 1-205, figs. 1-67. [p. 41]
«Genus Austrohinnites gen. nov.
Type species. Hinnites corioensis McCoy, 1879, Late Oligocene to Late Miocene, South Australia, Victoria and Tasmania.
Diagnosis. Chlamydini with a byssally attached, Chlamys-like juvenile stage and a thick, oyster-like adult stage RV cemented to hard substrates and growing into an irregular shape in conformity with the substrate; ‘Chlamys stage’ bearing prominent, coarse shagreen microsculpture; LV preradial dissoconch with microsculpture of very weak, antimarginally aligned pits and weak, widely spaced radial and commarginal ridges.
Remarks. It has long been unclear whether the large group of species traditionally included in Hinnites Defrance,1821 (type species: Ostrea crispa Brocchi, 1814, Pliocene, Italy; ?living, West Africa) is a monophyletic genus of cemented, oyster-like scallops, or a group of unrelated taxa lumped together on the basis of superficial morphology, representing several or many independent lineages that each developed an oyster-like habit from a Chlamys-like ancestor. An opinion favouring the latter alternative was expressed long ago by Dali (1908: 402). Bernard (1986) and Waller (1991: 22-23; 1993: 203-204) have reviewed the phylogenetic relationships of Hinnites-like pectinids. ‘Hinnites’ giganteus (Gray), living, northwestern North America, was provided with its own genus, Crassadoma, by Bernard (1986). Waller (1993) indentified a group of eastern Atlantic and eastern Pacific species that resemble C. gigantea closely in all characters other than having a cemented, ostreoid adult stage, and placed them all in Crassadoma, in its own tribe Crassadomini Waller, 1993; a new genus, Caribachlamys Waller, 1993, was also referred to Crassadomini. True Hinnites, including H. crispus (Brocchi) and the possibly synonymous, living West African H. corallinus (G. B. Sowerby I, 1828) (see Waller 1993: 203-204, for the complex nomenclatural history of this species) lacks shagreen microsculpture, and was thought by Waller (1993: 203) to be descended from Laevichlamys Waller, 1993. Contrary to the opinion of Dijkstra & Matsukuma (1993), Chlamys (‘Hinnites’) boninensis Dijkstra & Matsukuma, 1993 appears to lack true shagreen microsculpture, and clearly bears antimarginal ridgelets on the costae and interspaces of the ‘Chlamys stage’. This southern Japanese species belongs in Laevichlamys Waller, 1993 (H. H. Dijkstra 1999, pers. comm.). Pseudohinnites Dijkstra (1989) is another superficially similar but (to judge from its unusual, dorsally contracted auricles and distinctive, prominent radial sculpture) probably again independently evolved genus, living in deep water in New Caledonia and the Caribbean. Dijkstra & Knudsen (1997) recently showed that Pseudohinnites retains a very deep byssal notch and a functional ctenolium throughout life. Apparently it is not cemented to the substrate, and in the opinion of Dr T. R. Waller (1999, pers. comm.) belongs in the Pectinidae and actually is better not thought of as ‘hinitoid’. Harper (1991) discussed the role of predation in the evolution of the many, Paleozoic to Recent, independently evolved, cemented bivalves superficially resembling Hinnites.
The large, common Australian fossil ‘Hinnites’ corioensis McCoy is one of a group of Australian and New Zealand species sharing the distinctive characters of coarse, obvious, persistent shagreen microsculpture on the ‘Chlamys stage’ and, in some specimens, persisting onto the early cemented stage, and a distinctive, extremely weakly sculptured to virtually smooth LV preradial dissoconch. This therefore appears to be a monophyletic group, distinct from all other species referred previously to Hinnites. Following Waller’s (1993) example, it would seem logical to refer this group to the genus from which the cemented species were derived, but it is not at all clear what that genus was. Other Australian and New Zealand chlamydinine taxa with coarse shagreen microsculpture and very weak LV preradial dissoconch microsculpture are Equichlamys, which appears in Australia late in Pliocene time, after the ‘Hinnites' corioensis species group had become extinct, and Notochlamys. Notochlamys is assigned an Eocene (provisional) to Recent time range in Australia in the present work, but this is largely an artifact of not knowing the true phylogenetic relationships of the two pre-Pliocene species referred there. Undoubted Notochlamys is, again, a Pliocene to Recent genus, and we have not seen the LV preradial dissoconch sculpture of the pre-Pliocene species referred there. The only other possibly related species is ‘Chlamys’ mercuria Marwick, 1928 (Beu & Maxwell 1990: pl. 4e, f) from latest Paleocene-earliest Eocene rocks of Chatham Island. This small (12-20 mm high), chlamydoid species shares shagreen microsculpture with Austrohinnites, and provides a possible early member of the same phylogenetic group. The prominently and irregularly subdivided radial costae of the ‘Hinnites’ corioensis species group is a character that distinguishes it clearly from both Equichlamys and Notochlamys, as much as from all the other taxa described below. We do not know the origins of the ‘Hinnites’ corioensis species group, and as it has been a distinct phylogenetic unit in Australasia since at least Late Eocene time, it seems best recognised as a separate Australasian genus, Austrohinnites. The living North Pacific species Hinnites boninensis (Dijkstra & Matsukuma) obviously is not related to Austrohinnites, but the living West African ‘H’. ercolanianus Cocconi, 1873 and its European Miocene-Pliocene ancestors (Waller 1993: 202) have shagreen microsculpture, and the possibility that they are descended from Austrohinnites deserves investigation. Etymology. The prefix of the name (Latin, ‘austral’ = southern, + Hinnites) refers to the Southern Hemisphere
occurrence of the included species. Gender masculine. Species included in Austrohinnites gen. nov. at present are:
Austrohinnites corioensis (McCoy, 1879), Late Oligocene to Late Miocene; revised below. Austrohinnites marwicki (Allan, 1946), Middle Miocene, New Zealand. Austrohinnites polyaktinos (Ludbrook, 1955), Middle Miocene; revised below. Austrohinnites trailli (Hutton, 1873), late Early Miocene, New Zealand. Austrohinnites sp. nov.?, early Early Miocene, New Zealand. Austrohinnites sp. nov.?, Late Eocene, New Zealand.» ALAN GLENN BEU & THOMAS ALWYNNE DARRAGH, 2001
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Austrohinnites corioensis (McCoy); A. G. Beu & T. A. Darragh, 2001, Revision of southern Australian Cenozoic fossil Pectinidae, figures 9A (lectotype -designated here- of Pecten deformis Tate, = Hinnites tatei Cossmann, LV), 9B-9E.
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