The Echinoid Directory

• Test medium to large size, circular in outline and subconical in profile.
• Apical disc tetrabasal.
• Ambulacra weakly subpetaloid, pore-pairs adapically only weakly differentiated from ambital pore-pairs; narrow, petals I and V distally curve posteriorly.
• All ambulacral plates double pored.
• Periproct longitudinal, entirely surrounded by the circle of genital and ocular plates (i.e. the disc is endocyclic); opening into deep and sharp anal sulcus that runs from the apex to the posterior margin.
• Peristome slightly anterior, small and circular with vertical walled entrance.
• Bourrelets hardly developed; tuberculation confined to vertical walled entrance to peristome.
• Phyllodes with pore-pairs arranged into arcs of three forming a broad band; ambulacra tapering adorally and hardly depressed.
• No buccal pores.
• Tubercles perforate, crenulate, not arranged in vertical series, slightly larger on adoral surface.

Middle Jurassic (Aalenian-Bajocian) of Europe.

Clypeus constantini Cotteau, 1871, p. 228, by subsequent designation of Mortensen 1948, p. 109.

• Only the type species.

Irregularia, stem group Neognathostomata.

Monotypic; subjective junior synonym of Galeropygus Cotteau, 1856.

Mortensen (1948, p. 109) considered Ressopygus a synonym of Galeropygus. Kier (1962, p. 25) points out that the type species of both genera are very similar, differing only in that petals I and V distally curve posteriorly in R. constantini, whereas in G. agariciformis (=G. sublaevis) they curve anteriorly. Kier (1962, p. 27) thought that such a minor difference in not sufficient to warrant generic distinction.

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

T. Mortensen 1948. A monograph of the Echinoidea: 4 (1): Holectypoida, Cassiduloida. Reitzel, Copenhagen, 363 pp., 14 pls.

Barras, C. G. 2006. British Jurassic irregular echinoids. Monograph of the Palaeontographical Society no. 625 (part of volume 159 for 2005), 1-168, pls 1-14.