Eoastropecten Gale, 2020

Gale, Andrew S., 2020, A new comb-star (Asteroidea, Astropectinidae) from the Upper Triassic (Carnian) of China, Zootaxa 4861 (1), pp. 139-144 : 140-141

Genus Eoastropecten Gale , gen. nov.

Diagnosis. Astropectinid in which the superomarginals carry a sculpture of evenly-spaced, non-aligned fine rugosities on the raised central portion of the external surface. Inferomarginals embayed for articulation with actinal ossicles, externally with fine spine bases set in irregular rows, oblique to breadth of ossicles.

Type species. E. sechuanensis sp. nov.

Etymology. Formed from Ancient Greek ἠώς ľ(çṓs), “dawn”ľ and the genus name Astropecten , in reference to the new genus being the earlies known representative of the group.

Gender. Masculine.

Remarks. Most Jurassic to present day astropectinids have a consistent sculpture and spination of the supero- and inferomarginals; superomarginals bear rounded shallow pits which carry short, granular spines ( Figs 1A , 2J ), and inferomarginals have an oblique to transverse row of large, horseshoe-shaped or round ( Fig. 1B ) spine bases to which dagger-like spines are attached (e.g., Hess 1955; Jagt 2000; Gale 2011 ). In contrast, E. sechuanensis gen. et sp. nov. has evenly-sized, fine rugosities on the supero- and inferomarginals, which are aligned into oblique rows on the inferomarginals ( Fig. 2C ) and which are likely to have carried spines. A similar, but coarser sculpture of rugosities is seen on superomarginals of the Late Cretaceous “ Lophidiaster ” pygmaeus Spencer, 1913 (e.g., Jagt 2000, pl. 4: figs 1–7), but these are restricted to the abactinal part of the plate. “ Lophidiaster ” Spencer, 1913 is a nomen dubium to which diverse species have been referred, some of which are certainly not astropectinids. Astropectinid superomarginals with a sculpture like that of Eoastropecten gen. nov. are present in the Late Jurassic (Oxfordian; Fig. 2I ), but the associated inferomarginals lack the distinctive notch on the actinal margin present in the Triassic genus ( Fig. 2C, D ). A review and re-description of Mesozoic astropectinid material will be published at a later date.

Figures

FIGURE 1. Astropectinid morphology. A, B, Coulonia reidi (Blake & Reid, 1998), interradial fragment NHMUK PI EE 17699). A, abactinal surface, to show paxillae and superomarginals with intervening intermarginal fascioles. B, actinal surface, to show inferomarginal ossicles and imbricating actinal plates, in rows separated by grooves representing extensions of the intermarginal fascioles towards the ambulacral groove. C, Tethyaster sp. actinal surface, denuded of spines and smaller ossicles. Note the deep intermarginal fascioles, and the grooves extending across the actinal surface to the ambulacral groove. A.S. Gale Collection. A, B, Grayson Formation, Graysonites wacoense Zone, Cenomanian, Dottie Lynn Lane, Fort Worth, Texas, USA. C, present day, North Atlantic.

FIGURE 2. A–H, Eoastropecten sechuanensis gen. et sp. nov., marginal ossicles. A, E, holotype superomarginal in abactinal (A) and proximal (E) view (MHI2183/1). B, paratype superomarginal in proximal/distal view (MHI2183/6). C, D, paratype inferomarginal in actinal (C) and distal (D) views (MHI2183/3). B, paratype superomarginal in proximal/distal views (MHI2183/2). F–H, paratype superomarginals in abactinal view (MHI2183/4, /5). I, unidentified astropectind superomarginal in abactinal view (NHMUK EE 17700). J, astropectinid superomarginal in abactinal view (NHMUK PI EE 17701). K, L, marginals of living astropectinid Craspidaster hesperus (Müller & Troschel, 1840), J, superomarginal in abactinal view. K, L, supero-inferomarginal pair.A–H, Maantang Formation (Carnian, Triassic), sample C30, Jiancougou, Sechuan Province, China. I, Lower Oxfordian, Andelot-Morval, Départment du Jura, France. J–L, Recent, Hong Kong.