The Echinoid Directory

• Test of medium size, elongate, anterior and posterior margins usually rounded, adapically highly inflated, cylinder shaped
• Apical system anterior, tetrabasal, with four genital pores; may show sexual dimorphism of gonopore size (P. baghinensis)
• Petals broad, petal III shorter than others, poriferous zones narrow, tapering distally, interporiferous zones very wide, all ambulacral plates double pored
• Periproct inframarginal, transversely elongate, subtrigonal in outline
• Peristome large, oval or oblique
• Bourrelets slightly developed
• Phyllodes double pored, with two series in each half-ambulacrum
• No buccal pores
• Tubercles only slightly larger adorally

Barremian, Lower Cretaceous of France and Switzerland

• P. desmoulinsii L. Agassiz in Agassiz & Desor, 1847; Barremian, Early Cretaceous of France and Switzerland
• P. baghinensis Vaziri in Arab & Vaziri, 2010; Aptian of Iran

Lambert & Thiery (1909-1925) list some 13 species within this genus.

Irregularia; Cassiduloida; Pygaulidae

Pygaulus is very similar to Pygorhynchus. Kier (1962, p. 79) reports that both genera have similar petals, an oblique peristome, phyllodes with approximately the same number of pore-pairs in each series, and a longitudinal periproct. Pygaulus can be distinguished from Pygorhynchus by the shape of its test, being generally high, with a smoothly rounded anterior and posterior margin, parallel sides and an inframarginal periproct. In Pygorhynchus the test is generally lower, the posterior pointed, with sides not parallel, but expanding posteriorly, and the periproct being more marginal in its position.

Pygaulus is also morphologically similar to Plagiochasma, having a very similar petal arrangement, peristome and floscelle, but differs in having an inframarginal rather than a supramarginal periproct.

Agassiz, L. & Desor, J. E. 1846-1847. Catalogue raisonné des familles, des genres, et des espèces de la classe des échinodermes. Annales des Sciences Naturelles, Troisième Série, Zoologie: 6 (1846), 305-374, pls 15-16; 7 (1847), 129-168; 8 (1847), 5-35, 355-380.

A.L. Arab & M.R. Vaziri 2010. Sexual Dimorphism in a New Species of Cassiduloid Echinoid, Pygaulus baghinensis, from the Aptian Strata of Baghin Area, West of Kerman, Iran. Journal of Sciences, Islamic Republic of Iran 21, 43-47.
 

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

J. Lambert & P. Thiery. 1909-1925. Essai de nomenclature raisonnee des echinides. Libraire Septime Ferriere, Chaumont, 607 pp., 15 pls.