Clément, A. 2013. Révision des espèces Hemidiadema rugosum Agassiz, 1846, et H. neocomiense (Cotteau, 1869) (Euechinoidea, Camarodonta, Glyphocyphidae) du Crétacé inférieur du Bassin parisien (France). Carnets de Géologie [Notebooks on Geology] Mémoire 2013/01 (CG2013_M01), 1-57.

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Revision of the species Hemidiadema rugosum Agassiz, 1846, and H. neocomiense (Cotteau, 1869) (Euechinoidea, Camarodonta, Glyphocyphidae) from the Lower Cretaceous of the Basin of Paris (France).- Hemidiadema rugosum Agassiz, 1846, and H. neocomiense (Cotteau, 1869) are small and poorly known "regular" echinoid species. They were the source of much confusion due to their rarity and the inadequacy of their original descriptions. Both species are revised here to clarify their differences and taxonomic status. This revision is based on six specimens of H. rugosum (including the holotype, not shown by its original author), all from the locus typicus and stratum typicum (Clansayesian [Upper Aptian sensu gallico] "Grès ferrugineux" from Grandpré, Ardennes) and on a single specimen of H. neocomiense from the stratum typicum (Lower Hauterivian (? Lyticoceras nodosoplicatum Zone) "Calcaire à Spatangues" from Ville-sur-Saulx (Meuse), a locality near to the locus typicus (Auxerre, Yonne)). For this latter species, a neotype is designated to replace the holotype that is lost. Remarks on the paleoecology and stratigraphic and geographic distributions of these two species are given. The revision of these two species provides an opportunity to propose an emended diagnosis of the genus Hemidiadema Agassiz, 1846, a poorly known member of the Glyphocyphidae. Key Words: Echinoids; Glyphocyphidae; Hemidiadema; Lower Cretaceous; Hauterivian; Aptian; Paris Basin; France.

Echinoidea

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