Jurapecten infrajurensis, Gale & Jagt, 2021

Gale, Andy S. & Jagt, John W. M., 2021, The fossil record of the family Benthopectinidae (Echinodermata, Asteroidea), a reappraisal, European Journal of Taxonomy 755, pp. 149-190 : 162-164

Jurapecten infrajurensis sp. nov.

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Figs 6I–U, 7A–J

Diagnosis

Jurapecten in which the ambulacral base broadens abradially; sculpture of superomarginals comprises a reticulum of conjoined rugosities.

Etymology

From the Latin ‘ infra ’, in allusion to the occurrence of the species in the Lower Jurassic.

Material examined

The ambulacral illustrated here ( Fig. 6J) is the holotype ( NHMUK PI EE 17989 ); paratypes are NHMUK PI EE 17990–17995 . All specimens are from middle Toarcian strata at Le Clapier (Département d’Aveyron, 62 km WNW of Montpellier, southern France; see Thuy 2012). Additional paratypes are fifteen ossicles (SNSB-BGSP 2020 XLV 16–30) from the upper Toarcian–lower Aalenian (possibly aalensis ammonite Zone) at Quedlinburg (Landkreis Harz, northern Germany; see Hess 2014).

Description

Marginals block-like, length slightly exceeding height, carrying a sculpture of rugosities, on inferomarginals aligned into transverse rows parallel with arm ( Figs 6O, 7I). On proximal superomarginals ( Fig. 7C–D) rugosities discrete and centrally placed single spine base present; on distal superomarginals rugosities conjoined by narrow radial struts, forming a reticulum of imperforate stereom (e.g., Figs 6N, 7G). Ambulacrals ( Figs 6J–M, 7A, H) waisted, with elongated heads and broad flat bases; abactinal ridge absent ( Fig. 7A). Bases with broad padam site, slightly shorter than dadam ( Fig. 6J–L). Adambulacrals ( Figs 6P, R–T, 7B, E–F) with deep adadm site, distally placed padam and broad ada1 (best seen in Fig. 6R); ada3 diffuse. Orals ( Fig. 6I, Q) with tall, distally recurved apo, concave actinal face, low, lozenge-shaped body. Circumoral ( Fig. 6U) with elongated poda, short doda.

Remarks

Jurapecten infrajurensis sp. nov. differs from J. hessi (see above) in the more elongated ambulacral base, and the more coarsely rugose sculpture of both infero- and superomarginals, which lack enlarged spine pits.

Figures

Fig. 3. A–C. Terminology used for adambulacrals and orals in the present paper. A. Actinal view of adambulacral of Luidia sp. — B–F. Benthopecten simplex (Perrier, 1881), Recent (NHMUK EE 13563). B. Abactinal view of adambulacral. C. Interradial view of oral ossicle. D–E. Adambulacral in actinal (D) and abactinal (E) views. F. Base of ambulacral in actinal view. — G–I. Cheiraster gazellae Studer, 1883, Recent (A.S. Gale collection, unregistered), ambulacral ossicles in abactinal (G), actinal (H) and proximal (I) views; note raised abactinal ridge (abr) and inferomarginal articulation (ma). — J–M. Pontaster tenuispinus (von Düben & Koren, 1846), Recent (A.S. Gale collection, unregistered). J–K. Oral ossicle in radial (K) and interradial (J) aspects. L–M. Supero- and inferomarginal pair. Abbreviations: d = distal; p = proximal; see Material and methods; after Gale 2011a: figs 10, 16. Scale bars: 1 mm.