Contributed by Andrew Smith, October 2006
|Distribution||Upper Cretaceous (Cenomanian) of southern Europe; North Africa (including Niger) and the Middle East as far as Karakorum.|
|Type||Hemicidaris libyca Desor, in Agassiz & Desor, 1846, p. 338, by monotypy.|
|Classification and/or Status||Euechinoidea, Acroechinoidea, Diadematoida, Heterodiadematidae|
|Remarks||Although no lantern has yet been described from this taxon, it seems likely that Heterodiadema is a diadematoid, based on its tuberculation and deep buccal notches. It is very close to Trochodiadema in test morphology, but that genus has a regular apical disc that is not extended posteriorly. Juvenile Heterodiadema and Trochodiadema may be very difficult to differentiate.
Cotteau, G. H. 1862-1867. Paléontologie Française. Terrain Crétace, Tome Septième. Échinides. Masson et fils, Paris. 892 pp., pls 1007-1204.
Geys (1980) reported the presence of Heterodiadema lybica from the Campanian of Belgium, but this was based on an old museum collections and likely represents a mislabelled specimen.
Geys, J. F. 1980. Heterodiadema libycum (Agassiz & Desor, 1846) . a hemicidaroid echinoid from the Campanian of Belgium. Anales de la Societe geologique du Nord 99, 449-451.
Smith, A. B., Simmons, M. D. & Racey, A. 1990. Cenomanian echinoids, larger foraminifera and calcareous algae from the Natih Formation, central Oman Mountains. Cretaceous Research 11, 29-69.