The Echinoid Directory

Opisopneustes Gauthier, 1889, p. 2

Diagnostic Features
  • Test ovate with shallow anterior and posterior sulci. Frontal groove without well marked carinae.
  • Apical disc central with four gonopores. Hydropores scattered over anterior ocular and genital plates.
  • Paired ambulacra rather strongly flexed and with columns markedly unequal. Pore-pairs in posterior columns conjugate and elongate; those in the anterior column rudimentary especially adapically.
  • Frontal groove shallow adapically, becoming deeper and sharper below the ambitus and continuing adorally.
  • Peristome facing distinctly towards anterior; partially covered by labral plate in oral view (labral plate damaged in illustrated specimen).
  • Plastron plating ?protosternous with labral plate extending to touch second sternal plate.
  • Periproct supramarginal, just visible in oral view. Two subanal protuberances one on either side of the anal notch.
  • Aboral interambulacral plates with large primary tubercles adapically.
  • Marginal fasciole may be present.
Distribution
Upper Cretaceous (Campanian-Maastrichtian), North Africa, Middle East.
Name gender feminine
Type
Opisopneustes cossoni Gauthier, 1889, p. 2, by original designation.
Species Included
  • O. cossoni Cotteau & Gauthier, 1889; Campanian-Maastrichtian, Iran, Libya.
Classification and/or Status

Holasteroida, Hemipneustidae.

Monotypic

Remarks
Differs from Hemipneustes in having well-developed primary tubercles aborally forming prominent radial bands on adapical interambulacral plates, and by its flatter profile and marginal to supramarginal periproct. Lambert & Thiery (1920) stated that this genus differs from Hemipneustes in having a marginal fasciole. However, no fasciole was found on the adult specimen illustrated here from Libya.

Gauthier, V. 1889. Description des échinides fossiles recueillis en 1885 et 1886 dans la région sud des hautes-plateaux de la Tunisie, par M. Philippe Thomas. Exploration scientifique de la Tunisie, Géologie, Paléontologie, 116 pp., 32 pls. Imprimerie Nationale, Paris.