The Echinoid Directory

Medjesia Jeffery, 1997, p. 244

Diagnostic Features
  • Test ovate with rather shallow and wide anterior sulcus with weak carinae aborally.
  • Frontal groove well-marked on oral surface.
  • Apical disc with four gonopores. Ethmophract, with lateral ocular plates exsert and anterior and posterior pairs of genital plates abutting. Hydropores confined to genital plate 2.
  • Paired ambulacra flexed and with columns markedly unequal. Pore-pairs in posterior columns conjugate and elongate; those in the anterior column small and much less elongate.
  • Frontal groove continuous from apex to peristome; mouth circular and inclined towards the anterior.
  • Plastron plating protosternous with strongly V-shaped plates biserially alternating. Labral plate just contacting plate 5.a.2.
  • Periproct marginal, on vertical truncate face.
  • Aboral tuberculation fine and homogeneous.
  • Marginal fasciole present.
Distribution
Upper Cretaceous (Campanian), North Africa (Tunisia).
Name gender feminine
Type
Enallopneustes meslei Gauthier, 1892, p. 45, by original designation.
Species Included
  • Only the type species.
Classification and/or Status

Holasteroida, Hemipneustidae.

Monotypic.

Remarks

Differs from all other holasteroids in having an ethmophract apical disc (i.e. the four genital plates abut and are not separated into anterior and posterior pairs by ocular plates II and IV). The plastron plating shows that this taxon is a hemipneustid and not a spatangoid. Hemipneustes is most similar in petal structure and plastron plating. The species Hemipneustes jullieni is the immediate sister group to Medjesia, as in this species one of the pair of lateral ocular plates is exsert.

Jeffery, C. H. 1997. Revision of the echinoid Enallopneustes from the Upper Cretaceous of North Africa. Cretaceous Research 18, 237-248.