The Echinoid Directory

Echinocyamus van Phelsum, 1774, p. 131

[=Anaster Sismonda, 1842, p. 46, type species Anaster studeri Sismonda, 1842; =Echinocentrotus Checchia-Rispoli, 1907, explanation of pl. 17(2) (objective); = Lepidocyamus Mironov & Sagaidachny, 1984, p. 194, type species Echinocyamus crispus Mazzetti, 1893 ]

Diagnostic Features
  • Small ovate test with thick, rounded margins; rather flattened in profile.
  • Ten radial buttresses present internally.
  • Apical disc with four gonopores and a small number of scattered hydropores.
  • Petals small but usually distinct; open distally.
  • Peristome circular and a little sunken.
  • Pores and tube feet extending in bands over ambulacral following horizontal sutures but also extending onto interambulacral plates.
  • Interambulacral zones continuous; basicoronal plates relatively small with interambulacral elements larger than ambulacral elements.
  • Periproct oral, opening bounded by first and second paired interambulacral plates.
Distribution
Middle Eocene to Recent, widely reported.
Name gender masculine
Type
Spatangus pusillus Muller 1776, p. 18, by ICZN ruling, 1948.
Species Included
  • E. pusillus (Muller 1776); Pliocene-Recent, NE Atlantic.
  • E. crispus Mazzettii, 1894; Recent, Indo-Pacific
  • E. grandiporis Mortensen, 1907; Recent.
  • E. scaber de Meijere, 1902; Recent [includes E. macrostomus Mortensen, 1907].
  • E. incertus H. L. Clark, 1914; Recent.
  • E. sollers Koehler, 1922; Recent.
  • E. provectus de Meijere, 1902; Recent.
  • E. planissimus H. L. Clark, 1938; Recent.
  • E. platytatus H. L. Clark, 1914; Recent.
  • E. insularis Mironov & Sagaidachny, 1984; Recent.
  • E. lowraliensis Srivastava et al. 2009; Middle Miocene, India
  • E. megapetalus H. L. Clark, 1914; Recent.
  • E. (Lepidocyamus) crispus Mazzetti, 1893; Pleistocene-Recent, Indo-West Pacific [includes E. elongatus Clark, 1914, E. elegans Mazzetti, 1893].
  • E. prostratus Nisiyama, 1968; Pleistocene, Japan.
  • E. bisexus Kier, 1968; Middle Eocene, USA.
Classification and/or Status

Clypeasteroida; Scutellina; Laganiformes; Echinocyamidae.

Potentially paraphyletic by exclusion of Sismondia and the more derived Laganiformes.

Remarks

Distinguished from Fibularia and its relatives by having internal radial buttresses. Sismondia differs in having branched internal supports and more projecting basicoronal interambulacral plates. The Recent E. provectus de Meijere, 1902 has branched internal supports and is probably a juvenile Peronella. Mortensen (1948) recognized 18 extant species and there are in addition a number of fossil species of uncertain status. The oldest species based on excellent material is E. bisexus Kier from the Middle Eocene of Georgia, USA, described by P.M. Kier (1968). Mironov & Sagaidachny (1984) give a detailed account of the modern species. Zachos (2005) has discussed the distribution of this taxon in southeastern USA during the Eocene.

Mironov & Sagaidachny (1984) distinguished the monotypic subgenus Lepidocyamus on the basis of it having a small number of large periproctal plates and "squamiform projections along the peristome".

Mortensen, T. 1948. A Monograph of the Echinoidea IV.2 Clypeasteroida. C. A. Reitzel, Copenhagen.

J. W. Durham 1955 Classification of clypeasteroid echinoids. University of California Publications in Geological Sciences 31, 73-198.

Kier, P. M. 1968 Echinoids from the Middle Eocene Lake City Formation of Georgia. Smithsonian Miscellaneous Collections 153(2), 1-45, pls 1-10.

Nisiyama, S. 1968. The echinoid fauna from Japan and adjacent regions part II. Palaeontological Society of Japan Special Papers 13, 1-491, pls 1-30.

Mironov, A. N. & Sagaidachny, A. Y. 1984. Morphology and distribution of the Recent echinoids of the genus Echinocyamus (Echinoidea: Fibulariidae). Transactions of the P. P. Shirshov Institute of Oceanology 119, 179-204, 2 pls [in Russian].

van Phelsum, M. 1774. Brief aan Cornelius Noze- man, over de Gewelvslekken of Zee-egelen, p. 131 (explicaris tabulae I, II).

Zachos, L.G. 2005. Eocene dispersal of the echinoid genus Echinocyamus in the southeastern United States. Southeastern Geology 43(4), 215-227