The Echinoid Directory

• Test moderately large; flattened below, low subconical above.
• Apical disc dicyclic; genital plates large and pentagonal with subcentral gonopore; inner edge raised and with tubercles forming a periproctal ring. Ocular plates small and exsert. Plates smooth other than periproctal ring. Periproct subcircular.
• Ambulacra straight, widening to ambitus. Pore-pairs uniserial throughout; slightly larger aborally than orally, where they are also a little more arcuate.
• Ambulacral plating in triads; detailed compounding unknown. Primary tubercle on all but the more adapical plates; adapical tubercles relatively small.
• Interambulacral plates wider than tall. On aboral side with single primary tubercle close to adradial margin and broad naked interradial zone; no division separating the naked zone from the adradial band. At ambitus and adorally two subequal primary tubercles, reducing to one close to the peristome.
• Tubercles imperforate and non-crenulate; without areolar platform.
• Peristome small (about one-third test diameter) a little sunken, with shallow buccal notches ?with small tags.
• No sphaeridial pits (but preservation possibly not good enough to tell).
• No basicoronal plate with primary tubercle.
• Spines and lantern unknown.

Upper Oligocene - Lower Miocene, USA.

Coelopleurus aldrichi Clark, 1915, p. 158, by original designation.

• Only the type species.

Euechinoidea, Echinacea, Arbacioida, Arbaciidae.

Presumed monophyletic.

This taxon differs from Arbacia in having a much smaller peristome and no phyllodes. From Coelopleurus it is easily distinguished by its lack of a vertical ridge separating the interradial naked zone from the adradial tuberculate zone. It comes closest to Glyphopneustes in appearance, but is distinguished from that taxon by having two subequal primary tubercles on interambulacral plates at the ambitus and immediately below.

Cooke, C. W. 1959. Cenozoic echinoids from Eastern United States. Geological Survey USA Professional Papers 321, 106 pp, 43 pls.