The Echinoid Directory

• Test flattened below and domed above; circular to slighly pentagonal in outline; ambulacra inflated and interambulacra depressed adapically.
• Apical disc small, dicyclic. Genital plates large and pentagonal; ocular plates smaller. All plates more or less bare, decorated by epistroma. Periproct subcircular; in living species with four anal plates.
• Ambulacra straight, expanding to ambitus; generally rather inflated; aboral pore-pairs uniserial, subconjugate with the two pores rather widely separated and enlarged adapically, small and oblique adorally, remaining uniserial to peristome edge.
• Plating in arbaciid triads throughout, with upper and lower elements as demiplates and each triad dominated by a large primary tubercle; no perradial granular zone.
• Interambulacra a little wider than ambulacra. Above ambitus plates differentiated into an interradial sunken and naked zone, without tubercles, and outer, narrower adradial bands. A vertical ridge marks the boundary between the two zones. Adradially there is usually a small primary tubercle on each plate, except on the most adapical plates.
• At the ambitus interambulacral plates with two subequal primary tubercles; the inner series continuing just a little above the ambitus.
• Primordial interambulacral plate present at peristome edge, with primary tubercle.
• Primary tubercles imperforate and non-crenulate. The areole forms a slightly raised platform on the plate.
• Peristome subcircular or subpentagonal, large (about half test diameter). Buccal notches feeble with long, well developed tags.
• Sphaeridial pits multiple and placed along perradius.
• Spines much longer than test diameter; slender, curved, ending in a short hyaline cap; triangular in cross-section.

Eocene to Recent, Europe, North Africa, North America; India, Australia, Caribbean, Indo-Pacific.

Coelopleurus equis Agassiz, 1840, p. 12 [=Cidaris coronalis Leske, 1778, p. 136, by monotypy.

• C. coronalis Agassiz, 1846; Lutetian, Europe, North Africa [=C. delbosi Desor, 1857; Lutetian, France; = C. munieri Cotteau, 1892; Middle Eocene, Europe].
• C. isabellae Cotteau, 1892; Eocene, Spain.
• C. douvillei Cotteau, 1892; Lutetian, France.
• C. forbesi d'Archiac & Haime, 1854; Eocene, India.
• C. arnaudi Cotteau, 1883, Oligocene (Rupelian), France.
• C. infulatus (Morton, 1833); late Middle Eocene, eastern USA.
• For other species see the subgenera Keraiophorus, Phrissopleurus, Coelopleurus and Murravechinus

Euechinoidea, Echinacea, Arbacioida, Arbaciidae

Distinguished from Arbacia by its multiple sphaeridial pits and the demarcation of adradial and interradial zones of the aboral interambulacra.  Carrasco  (2007) described sexual dimorphism in the type species.

Agassiz, L. 1840. Catalogus systematicus Ectyporum Echinodermatum fossilium Musei Neocomiensis, secundum ordinem zoologicum dispositus; adjectis synonymis recentioribus, nec non stratis et locis in quibus reperiuntur. Sequuntur characteres diagnostici generum novorum vel minus cognitorum, 20 pp. Oliv. Petitpierre, Neuchâtel.

Carrasco, J. F. 2007. Dimorfismo sexual en Coelopleurus coronalis (Echinoidea, Eoceno). Batalleria 13, 15-28.

Mortensen, T. 1935. A monograph of the Echinoidea II. Bothriocidaroida, Melonechinoida, Lepidocentroida and Stirodonta. C. A. Reitzel, Copenhagen.