The Echinoid Directory

• Test ovate and rather depressed in profile; no frontal sulcus.
• Apical disc disjunct with ocular plates II and IV in contact behind genital plate 2. Genital plates 1 and 4 separated from posterior ocular plates. There may be a catenal plate between oculars II and IV.
• Posterior ocular plates in contact with periproct so that ambulacral columns converge on the upper margin of the periproct; extremely elongate and forming the lateral margins of the periproct.
• Periproct on vertical truncate face and associated with a shallow subvertical sulcus.
• Peristome small and circular.
• Ambulacra non-petaloid; pore-pairs small oblique and simple throughout; ambulacrum III undifferentiated.
• Short phyllodes developed adorally with occluded plates.
• Plastron protosternous.

Lower and Middle Jurassic (Toarcian - Callovian); Europe.

Disaster ringens Agassiz, 1836, p. 183, by subsequent designation of Lambert & Thiery, 1924, p. 390.

• P. ringens (L. Agassiz, 1839); Upper Bajocian to Upper Callovian of Europe.
• P. magnus Solovjev, 1971; Callovian, former Soviet Union.
• P. castanea Desor, 1858 [=P. pseudoringens (Cotteau, 1867)]; Callovian, Europe, former Soviet Union.

Irregularia, Stem group Atelostomata, Pygorhytidae.

?Paraphyletic.

Distinguished from other pygorhytids by its vertical truncate posterior with shallow anal sulcus. In Pygomalus the ambulacra and the peristome are not sunken, in contrast to Pygorhytis.

P. castanea is intermediate between Pygorhytis and Cyclolampas. Like Cyclolampas it has a posterior apical disc and strongly conical profile, inframarginal periproct, and well developed phyllodes adorally with pore-pairs in three offset columns. However, unlike Cyclolampas the posterior oculars remain in contact with the periproct and the posterior genital plates abut directly against ocular plates II and IV.

Barras, C. 2006. British Jurassic irregular echinoids. Monograph of the Palaeontographical Society, 1-168, pls 1-14 (publication number 625).

Jesionek-Szymanska, W. 1963. Echinides irreguliers du Dogger de Pologne. Actes Palaeontologica Polonica 8(3), 293-396, pls 1-7.

Pomel, A. 1883. Classification méthodique et Genera des Échinides vivante et fossiles. Thèses présentées a la Faculté des Sciences de Paris pour obtenir le Grade de Docteur ès Sciences Naturelles 503, Aldolphe Jourdan, Alger, 131 pp.

Solovjev, A. 1971. Late Jurassic and Early Cretaceous disasterids of the USSR. Transactions of the Palaeontological Institute, Academy of Sciences of the USSR 131, 1-120, pls 1-16 [in Russian]