Micropetalon reportedly differs from Echinoneus in having genital plates that are distinct, pore zones that are not depressed, pore pairs without peripodia and imperforate primary tubercles (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.
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