The Echinoid Directory

• Test large; presumed depressed; only interior of oral surface known.
• Apical disc unknown.
• Ambulacra as wide as interambulacra towards ambitus; biserial adorally but quadriserial towards ambitus with occasional occluded plates in between the two series.
• Pore-pairs central and uniserial adorally, forming multiple columns towards ambitus.
• Internal perradial flanges only on proximal two or three plates.
• Interambulacral zones taper adorally to a basicoronal plate; towards ambitus there are 5 discrete columns; plates polygonal, not in well-defined rows.
• Tuberculation unknown.
• Peristome small; lantern and spines unknown.

Lower Carboniferous (Tournaisian) of Ireland.

Protoechinus anceps Austin, 1860, p. 446, by original designation.

• Only the type species.

Stem group Echinoidea; ?Proterocidaridae.

Monotypic.

This taxon is based on a single specimen showing the interior of the ?oral surface. In the past it has been treated as a synonym of Pholidocidaris (e.g. Jackson 1912). However, the biserial adoral ambulacral plating differentiates it from that genus. Hyattechinus has biserial plating, but in that taxon the ambulacra remain biserial throughout, whereas in Protoechinus the ambulacra become quadriserial towards the ambitus. Given these differences it seems prudent to retain Protoechinus as a valid taxon.

Austin, T. 1860. The Geologist 3, p. 446.

Jackson, R. T. 1912. Phylogeny of the Echini, with a revision of Palaeozoic species Memoirs of the Boston Society of Natural History 7, 491 pp. 76 pls.