The Echinoid Directory

Micropetalon A. Agassiz & Clark, 1907, p. 251

Diagnostic Features
  • Test of moderate size, ovoid, margin broadly rounded, oral surface sunken towards the peristome.
  • Apical disc central, tetrabasal with four gonopores.
  • Ambulacra narrow, petals undeveloped, typically with simple ambulacral plating throughout, pores single throughout.
  • Tubercles imperforate.
  • Periproct oral, very large, oblique, close to the peristome.
  • Peristome large, central or slightly anterior, oblique, slightly depressed.
  • Bourrelets absent.
  • Phyllodes undeveloped.
  • No buccal pores.
  • No naked sternal area.
Recent, Indo-Pacific.
Name gender neuter
Micropetalon purpureum A. Agassiz & Clark, 1907, p. 251; by original designation.
Species Included
  • M. purpureum A. Agassiz & Clark, 1907; Recent, Indo-Pacific.
Classification and/or Status
Irregularia; Echinoneina; Echinoneidae.

Micropetalon reportedly differs from Echinoneus in having genital plates that are distinct, pore zones that are not depressed, and pore pairs without peripodia (Durham et al. 1966). The periproct as well as the peristome appear to be oblique in Micropetalon. In the type species of Echinoneus only the peristome is oblique, the periproct being longitudinally ovate. From Koehleraster it additionally differs by its imperforate primary tubercles.

Agassiz, A & Clark, H. L. 1907 Bulletin of the Museum of Comparative Zoology, Harvard 50, p. 251.

J. W. Durham, K. E. Caster, H. Exline, H. B. Fell, A. G. Fischer, D. L. Pawson, G. Regnell, W. K. Spencer, G. Ubaghs, C. D. Wagner, and C. W. Wright. 1966. Treatise on Invertebrate Paleontology, Part U Echinodermata 3. The Geological Society of America and The University of Kansas Press, 2, pp. U367-U695.

A. M. Westergren. 1911. Reports on the results of the expedition to the tropical Pacific. Echini: Echinoneus and Micropetalon. Memoirs of the museum of comparative zoology, 15, 34 pp., 31 pls