The Echinoid Directory

• Test subovate, of small to medium size, ovate with truncate posterior; oral surface slightly sunken towards the peristome.
• Apical system slightly anterior, tetrabasal, with four gonopores, posterior oculars elongate, no catenal plates.
• Petals long, parallel, open, extending two-thirds of the way to ambitus, inner pore round, outer pore slightly elongated transversely; all ambulacral plates with double pores.
• Periproct towards the rear of the aboral surface; supramarginal, bordering on marginal, on an almost vertical face, with a short groove extending from lower edge of periproct to posterior edge of test.
• Peristome anterior, pentagonal, depressed, wider than high.
• Bourrelets absent.
• Phyllode structure unreported.
• No naked zone in posterior interambulacrum orally.

Early Cretaceous (Valanginian) of Algeria.

• Only the type species.

Irregularia; Neognathostomata; 'nucleolitid'.

Subjective junior synonym of Phyllobrissus Cotteau, 1859.

Cotteau et al. (1876-1884) distinguished the type species of Thigopygus because of its depressed form and the position of the periproct. It is very similar in appearance to the type species of Phyllobrissus, having a more marginal periproct, on an almost vertical face, with only a short groove extending from the lower edge of the periproct to the posterior edge of the test. This differentiates it from Nucleolites,which has a supramarginal periproct and a distinct anal sulcus.

G. Cotteau, P. A. Peron & V. Gauthier. 1876-1884. Echinides fossiles de l'Algerie, vol. I, Paris. Fasc. I 1883, Terrain Jurassique, 79 pp., 8 pls.; Fasc. 2, 1884, Etages Tithonique et Neocomien, 99 pp., 9 pls.; Fasc. 3, 1876, Etages Urgo-aptian et Albian, 90 pp., 8 pls.; Fasc. 4, 1878, Etage Cenomanien, pp. 1-144, pls 1-8; Fasc. 5, 1879, Etage Cenomanien (concluded), pp. 145-234, pls. 9-16. G. Masson, Paris.

P. M. Kier. 1962. Revision of the cassiduloid echinoids. Smithsonian Miscellaneous Collections, 144 (3) 262 pp.