Talochlamys multilamellata 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. 106, figs. 35A-C, E]
2001 Talochlamys multilamellata Beu & Darragh, 2001
A. G. Beu & T. A. Darragh, 2001, figure 35.
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«Description. Moderate-sized for genus (to c. 33 mm high), acline to very weakly prosocline, the two valves similarly and only moderately weakly inflated, equidimensional to slightly longer than high; umbonal angle c. 110°. LV preradial sculpture not seen. Disc sculpture of c. 38-42 moderately elevated, moderately wide radial costae, with each radial interspace slightly to markedly narrower than one costa, costae subdividing to form pairs of similar costae over part of disc of many specimens, intercalating major secondary costae in a few interspaces of some specimens, and intercalating minor, low, narrow secondary costellae over distal half of disc on many specimens, regularly arranged in centre of each interspace on a few specimens; crossed by many low, rather closely spaced commarginal lamellae, raised into low, simple scales normal to costae on costal crests and across interspaces of closely spaced, subdivided costae, but only weakly continuous as low growth ridges across primary radial interspaces; scales extend laterally beyond costal margins in interspaces of well preserved specimens and form low, triangular projections extending beyond costal margins on some specimens. Floor of intercostal spaces bearing low, narrow, closely spaced antimarginal ridgelets over entire shell, ridgelets straighter than in T. keiloriana, not obviously broken up into radiating ‘bundles’ at commarginal ridges. Auricles low, moderately wide; RV anterior auricle with moderately deep, narrow byssal notch, deeply depressed byssal fasciole and functional ctenolium in adult; ctenolium with 4-5 stout, hooked teeth; outer face of auricle, above byssal fasciole, sculptured with 5-6 low, wide, coarsely scaly radial costae. LV anterior auricle moderately tall, anterior margin slightly sinuous, inclined weakly towards anterior; sculptured with c. 10 low, wide, closely spaced, scaly radial costae; posterior auricles moderately tall, with only weakly concave posterior margins inclined weakly towards anterior; dorsal margins of RV auricles finely serrate. Interior smooth except for weakly notched ventral margin. Hinge (seen only in one incomplete RV) with very thin dorsal teeth and short, very thin, low, widely diverging resilial teeth.
Dimensions.
Holotype, WAM 69.815a H 32.4 L 33.4 RV Paratype, WAM 69.815b 27.0 28.1 RV Paratype, WAM 69.815c 28.6 28.5 LV Paratype, WAM 69.815d 26.6 26.5 LV Type material. WAM 69.815, Abrakurrie Limestone (Longfordian), spoil from well at ruin, Moodini Bluff, Eucla Basin, c. 23 km east of Madura roadhouse, at foot of Hampton Escarpment, southeastern Western Australia, grid ref. Madura 530054, coll. T. A. Darragh, M. Archer & G. W. Kendrick, 5.iii.1969; holotype, WAM 69.815a, a large RV, and 9 paratypes.
Other material examined. NMV P300550, all data as above (1 specimen). Occurrence and time range. Known only from a single block of Abrakurrie Limestone (Longfordian) collected from well spoil. Likely to occur widely in Abrakurrie Limestone in the Eucla Basin.
Remarks. Talochlamys multilamellata sp. nov. bears a close general resemblance to T. keiloriana, but they are distinct in many characters. The radial costae of T. multilamellata are much more irregularly subdivided and intercalated than those of any of the other species referred here to Talochlamys, except for the Recent T. pulleineana. The shape of T. multilamellata is considerably lower, wider and more weakly inflated than in most other species referred here to Talochlamys, although T. badioriva sp. nov. is, if anything, more weakly inflated than T multilamellata. The costal scales also are wider, lower and simpler than in all the other species referred to Talochlamys here; although resembling those of the other species closely in appearance, they are simple, thin flanges rather than hooked or cupped scales (but all the material has been removed from hard limestone, so part of the scales might have been broken off all the material). Finally, the ‘bundles’ of short lengths of antimarginal ridgelets, broken up by ventrally convex growth lines, that characterise the other Australian fossil species of Talochlamys are not seen in T. multilamellata, in which the antimarginal ridgelets are simple and straight near the centre of the disc. Nevertheless, the close overall resemblance to T. keiloriana is taken as evidence of relationship at present, for want of other criteria. T. multilamellata has a curious mixture of chlamydinine characters (irregularly subdivided and intercalated costae, simple antimarginal ridgelets in all radial interspaces, lack of internal rib carinae) and more advanced characters (the rather low, wide shape, and the wide umbonal angle with low, wide ears) and its true taxonomic position will not be clear until the LV preradial sculpture can be revealed. Talochlamys multilamellata occurred in the same block as Abrachlamys toolinnensis gen. nov., sp. nov., named above, although the latter was much the less common of the two; A. toolinnensis occurs more widely than T. multilamellata in the Abrakurrie Limestone samples available to us, and is easily distinguished by having very little costal subdivision, and by having costal scales on the disc of the LV only, rather than on both valves as in A. toolinnensis. Etymology. The specific name (Latin, ‘multus’, many + 'lamella', a lamella or thin plate) refers to the unusually numerous, prominent scales of the type species.» ALAN GLENN BEU & THOMAS ALWYNNE DARRAGH, 2001
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