Equichlamys Iredale, 1929
IREDALE, T. 1929. Mollusca from the continental shelf of eastern Australia. No .2. Records of the Australian Museum, 17: 157-189. [p. 162]
«Four very distinct series are at once noted, the asperrimus, lividus, bifrons and "hedleyi" groups, and it will clarify matters to designate these groups as genera, so I herewith propose Mlimachlamys "with P. asperrimus as type, Scaeochlamys with Pecten lividus as type, Equichlamys with P. bifrons as type and Mesopeplum with M. caroli as type.
(...)
Equichlamys, on the other hand, is a much larger flattened inequivalve form with the ears small and subequal, byssal gape small, almost missing, and pectinidial teeth almost obsolete in mature shells, though present in young specimens. Seven to nine distant compound ribs have their broad intervals filled with fine radials. the whole covered with "Camptonectes" sculpture. These large ribs are well marked internally, but, while with age the superficial ribs have a strong tendency to disappearance, the internal ridges become more pronounced, suggesting those of Amusium. The right valve is tightly clasped by the left, with the sides open, another Amusioid feature.»
TOM IREDALE, 1929
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Pecten bifrons Lamarck; L. A Reeve, 1852-1853, Monograph of the genus Pecten. In: L. A. Reeve (Ed.), 1843-1878, Conchologia Iconica; or illustrations of the shells of molluscous animals, volume 8, plate 12, figure 45.
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Equichlamys bifrons (Lamarck); H. H. Dijkstra & A. G. Beu, 2018, Living scallops of Australia and adjacent waters, figures 63B, 63D-63H.
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«Equichlamys Iredale, 1929: 162. Type species (by original designation): Pecten bifrons Lamarck, 1819; late Pliocene to Recent, southeastern Australia.
Diagnosis. Plicate Pedini with aequipectinoid shell shape, inflation of valves almost equal, acline or weakly prosocline, auricles almost equal in size; coarse shagreen microsculpture present throughout ontogeny; internal rib carinae prominent; hinge with prominent resilial and dorsal teeth; byssal notch shallow, ctenolium obsolete or lacking in late ontogeny.
Distribution. Late Pliocene–Recent (Beu & Darragh, 2001). Southeastern Australia, living in the littoral to sublittoral zones on soft sediment (muddy sand or sand) with seagrass beds.
Discussion. Hertlein (1969: N357) treated Equichlamys as a subgenus of Chlamys Röding, 1798 in the Chlamys group. Waller (1991: 30) considered it to be a representative of the suprageneric Chlamys group or, more recently, in Chlamydini (i.e., Pedini) (Waller, 1993, 2006a).
Waller (1991: 30) compared the morphological convergence of Equichlamys and Notochlamys and suggested that the two are not closely related and have different ancestries. As Equichlamys and Notochlamys are almost the only examples of internally carinate Pedini, they provide examples of Pedini that have evolved internal rib carinae independently from non-carinate ancestors. For biostratigraphy of Equichlamys see Beu & Darragh (2001).» DIJKSTRA, H. H. & A. G. BEU. 2018. Living scallops of Australia and adjacent waters (Mollusca: Bivalvia: Pectinoidea: Propeamussiidae, Cyclochlamydidae and Pectinidae). Records of the Australian Museum, 70 (2): 113-330, figs. 1-102. [p. 232]
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