The Echinoid Directory

Anisopetalus Clark in Arnold & Clark, 1927, p. 44

Diagnostic Features
  • Test of medium size, elongate, with smoothly rounded anterior margin; short truncated posterior; low with gently sloping sides, adoral surface flat.
  • Apical system anterior, monobasal with four gonopores.
  • Petals broad, of equal length, weakly bowed and closing distally. Poriferous zones narrow, the two columns of unequal length in the holotype: six more pore pairs in right poriferous zone in petal III than in left, two more in posterior poriferous zones of petals II and IV than in anterior zones, and approximately five more in outer poriferous zones of petals V and I.
  • Pores conjugate, outer pore slightly elongated transversely, inner pore round. Interporiferous zones wide, almost three times as wide as poriferous zones.
  • Periproct marginal to slightly supramarginal, transverse with slight subanal groove.
  • Peristome anterior, small, pentagonal, transverse.
  • Bourrelets confined to vertical walled entrance to peristome; slightly convex.
  • Phyllodes single pored, pores arranged in two series in each half-ambulacrum; approximately eight in each outer series, four or five in each inner. Sphaeridia pits in two rows along midline of ambulacrum.
  • Buccal pores present.
  • Tubercles larger adorally, with naked, slightly pitted area in interambulacrum 5 and ambulacrum III.
Eocene, Jamaica.
Name gender masculine
Anisopetalus ellipticus Clark in Arnold & Clark, 1927, p. 45, by original designation.
Species Included
  • Only the type species.
Classification and/or Status

Irregularia; Cassiduloida; Cassidulidae.

Monotypic; subjective junior synonym of Ryncholampas A. Agassiz, 1869.


Kier (1962) states that Arnold & Clark distinguished their genus from Cassidulus on the grounds that the petals in Anisopetalus have poriferous zones of unequal length. He points out that Cooke (1959) reported that the poriferous zones in Cassidulus and Ryncholampas are also unequal.

B. W. Arnold & H. L. Clark 1927. Jamaica fossil Echini; with descriptions of new species of Cainozoic Echinoidea by H. L. Hawkins. Memoirs of the Museum of Comparative Zoology, Harvard 50, (1), 84 pp., 22 pls, 3 figs.

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