The Echinoid Directory

• Test of medium size, circular to pentagonal, with width equal to length, low domed in profile with greatest height at apical system; oral surface flat to slightly depressed around peristome.
• Apical system central, tetrabasal, genital 2 much larger than other genital plates, extending posteriorly, separating posterior genital and ocular plates. Other genital plates very narrow and elongated.
• Petals very broad, open distally, equal in length, extending to margin; poriferous zones very wide, tapering distally, outer pore of pair slit-like, inner round to slightly elongated transversely, joined by deep conjugation groove.
• Periproct supramarginal, well removed from the apical disc; longitudinal, in shallow groove extending to posterior margin.
• Peristome anterior, pentagonal, width approximately equal to length.
• Bourrelets poorly developed, confined to vertically sided entrance to peristome.
• Phyllodes not widened, very long, double pored, with many pore pairs arranged in two series, every third pore-pair displaced perradially.
• No buccal pores.

Middle Jurassic (Bathonian - Callovian) of Somalia.

Clypeus wylliei Currie, 1925, p. 63; type species by subsequent designation of kier, 1962, p.37.

• Dactyloclypeus wylliei (Currie, 1925); Middle Jurassic, Somalia.

Irregularia; Neognathostomata; 'nucleolitid'.

Subjective junior synonym of Crotoclypeus.

Maccagno erected Dactyloclypeus as a new subgenus of Clitopygus considered by Kier (1962) to be a synonym of Nucleolites. Dactyloclypeus is closer morphologically to Clypeus than Nucleolites. In erecting a subgenus of Clitopygus, Maccagno may have been referring to the work of Lambert & Thiery (1925, p. 586), who synonymised Clitopygus with Crotoclypeus on the basis of the position of the periproct.

Dactyloclypeus is very similar to Clypeus, but has its periproct far removed from the apical disc, opening towards the posterior margin and with only a very short anal sulcus.

Dactyloclypeus may be distinguished from Galeropygus by its well-developed petals. Nucleolites is very similar, but has less well-developed petals, is more subquadrate in outline, and has a distinct inner and outer series of pore-pairs in its phyllodes rather than a broad band of overlapping arcs.

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