Leoclunipecten Beu & Taviani, 2014
BEU, A. G. & M. TAVIANI. 2013. Early Miocene Mollusca from McMurdo Sound, Antarctica (ANDRILL 2A drill core), with a review of Antarctic Oligocene and Neogene Pectinidae (Bivalvia). Palaeontology, 56 (6): 1-44, figs. 1-9. [p316]
«Genus LEOCLUNIPECTEN gen. nov
LSID. urn:lsid:zoobank.org:act:8757C008-7145-488F-BCD1-1F7D7A671D7C
Type species. Austrochlamys gazdzickii Jonkers, 2003.
Occurrence of type species. Late Early Oligocene (Rupelian), Polonez Cove Formation and possibly Boy Point Formation, Lion’s Rump area (Jonkers 2003, fig. 4a), King George Island, South Shetland Islands.
Derivation of name. From Latin, leo (lion) and clunis (buttocks or rump), combined with the suffix pecten (Latin, a comb), used for the names of many scallops; referring to the type area of the type species, the Lion’s Rump, King George Island; ‘the Lion’s Rump scallop’. Gender masculine.
Diagnosis. A genus of moderate-sized Chlamydini with a relatively long (antero-posteriorly), weakly inflated disc; umbonal angle c. 115 degrees. Macrosculpture of c. 65–75 low, flat-crested, closely spaced radial costae, with sharply defined edges and flat-bottomed interspaces; microsculpture of widely spaced, prominent commarginal ridges and very fine antimarginal ridgelets. Byssal notch wide, deep; byssal notch and ctenolium functional in adults; LV anterior auricle tall; posterior auricles short, with forwardsloping, concave posterior outlines.
Included species. The one other species we are aware of that might possibly be considered to belong in Leoclunipecten gen. nov. is ‘Chlamys’ mawsoni Fletcher, 1938 (Fletcher 1938, p. 106, pl. 10, figs 1–2; Jonkers 2003, p. 57, pl. 15, fig. e) from Ronarc’h Peninsula, Kerguelen Island, of Miocene age (Lauriat-Rage et al. 2002; locality: Jonkers 2003, fig. 13) (holotype: South Australian Museum, Adelaide, T1368; plaster cast examined GNS WM5536). Jonkers (2003, pp. 57–59) commented on the apparently great convexity of the one known incomplete, distorted specimen (a LV), the unusually tall LV anterior auricle, and the lack of commarginal ridges on the disc. However, it appears that the great inflation is a distortion artefact. The holotype of C. mawsoni is similar to Leoclunipecten gen. nov. gazdzickii in having at least 70 low, narrow, closely spaced radial costae and no other obvious sculpture, but the lack of commarginal sculpture suggests that C. mawsoni is not related to Leoclunipecten gen. nov. Fuller analysis of the relationships of C. mawsoni must await the collection of better material, including the RV.
Remarks. It is obvious on comparing specimens of Austrochlamys natans (type species of Austrochlamys Jonkers, 2003; Jonkers 2003, pl. 15, figs a–b), A. anderssoni (Fig. 3D; Jonkers 2003, pl. 13, figs a–g) and ‘Austrochlamys’ gazdzickii (Jonkers 2003, pl. 12, figs a–d) that these species belong in two distinct genera. ‘Austrochlamys’ gazdzickii has a much larger number of lower, narrower, more uniform, much more closely spaced radial costae and a wider, much flatter disc than in the species we consider to be correctly assigned to Austrochlamys sensu stricto, listed above. Jonkers (2003, p. 64) pointed out that ‘A’. gazdzickii differs from A. natans in its longer (antero-posteriorly) and more nearly equidimensional disc, its markedly lesser convexity, its much higher number of radial costae (c. 65–75 similar costae, compared with c. 30–39 primary costae and 10–15 intercalated and bifurcated secondary costae on A. natans, and c. 30 primary costae and c. 30–40 intercalated and bifurcated secondary costae on A. anderssoni) that are lower, narrower, more sharply defined and much more closely spaced than in Austrochlamys, its more widely spaced commarginal ridges, its markedly deeper byssal notch with more nearly parallel dorsal and ventral margins of the longer RV anterior auricle, and its greater auricular asymmetry. The RV anterior auricle is much longer and narrower, and the RV posterior auricle is shorter and more forward-sloping in Leoclunipecten gen. nov. gazdzickii than in species we refer to Austrochlamys. In our opinion, these differences are generic characters, and we propose the new genus Leoclunipecten to include ‘Austrochlamys’ gazdzickii.»
ALAN GLENN BEU & MARCO TAVIANI, 2014
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Leoclunipecten gen. nov. gazdzickii (Jonkers), paratype, RV; A. G. Beu & M. Taviani, 2014, Early Miocene Mollusca from McMurdo Sound, Antarctica (ANDRILL 2A drill core), with a review of Antarctic Oligocene and Neogene Pectinidae (Bivalvia), figure 6A.
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