Valettaster thuyi, Gale, 2021

Gale, Andrew Scott, 2021, Taxonomy and phylogeny of the ‘ football stars’ (Asteroidea, Sphaerasteridae), Journal of Systematic Palaeontology 19 (10), pp. 691-741 : 734-735

Valettaster thuyi sp. nov.

( Fig. 22M, N )

Type. The specimen figured here ( Fig. 22M, N ) is the holotype, from the Hildoceras bifrons ammonite Zone (Toarcian) at Fougerolles, France ( MHNML 2020.1.1) .

Diagnosis. Valettaster with tabulate abactinal ossicles, the broad outer surface of which bears a branching reticulum of imperforate stereom.

Derivation of name. After Ben Thuy , who sent the holotype specimen to the author .

Material. Holotype, a single abactinal ossicle, obtained by Marc Chesnier from washed residues from the Gúerin quarry at Fougerolles, Normandy, France (see Hess & Thuy 2016 for details).

Description. Abactinal ossicle with outline irregularly semicircular, 3 mm in maximum dimension; one side is straight, the other bearing irregular short lobes. The ossicle is flat, with a broad external surface slightly narrower than basal breadth. The external surface shows a radial network of irregularly bifurcating ridges of smooth imperforate stereom.

Remarks. This is by a considerable margin the oldest known representative of Valettaster (185–190 Ma), and the similarity of its highly specialized sculpture (reticulum of imperforate stereom) to that of the Cretaceous V. argus and V. ocellatus confirms its placement in the genus. It differs from V. ocellatus in the thinner abactinals, the very broad external surface and the irregularly bifurcating, radial ribbing. In V. ocellatus the abactinals are stout truncated cones, and the sculpture comprises fine radial ridges and pustules ( Fig. 22E ).

Figures

Figure 22. A–D, G, J, Valettaster digitatus (Quenstedt, 1858), abactinal ossicles, in external view (A, C, D, G, J) and lateral view (B) (GPIT/A5/50). E, Valettaster ocellatus (Forbes, 1848), abactinal ossicle, in external view (NHMUK EE 17696). F, I, Pouzaster pocknotata gen. et sp. nov., abactinal ossicles in external view (MHNML 2020.1.2, 1.3). H, K, Valettaster granulatus (Brunnich Nielsen, 1943), abactinal ossicles, external view (SNSB-BSGP 2020 XLV1, 2). L, Valettaster argus (Spencer, 1907), articulated group of abactinal ossicles (NHMUK EE 17637f). M, N, Valettaster thuyi sp. nov., holotype, abactinal ossicle in external and lateral views, respectively (MHNML 2020.1.1). Provenance: A–D, G, J are from the Oxfordian of Oerlingen, south Germany. B is from the Santonian of East Kent, UK. F, I are from the serpentinus ammonite Zone, Toarcian at Fougerolles, France. H, K are from the lower Maastrichtian of R¨ugen, Germany. M, N are from the bifrons ammonite Zone, Toarcian, Fougerolles, France. L is from the coranguinum Zone, Santonian, Broadstairs, Kent, UK. Scale bars: A–E, G, H, J, K = 5 mm; F, I, L = 0.5mm; M, N = 0.2 mm.