The Echinoid Directory

Contributed by Andrew Smith, August 2011

Acriaster Smith, in Smith & Bengtson, 1991, p. 46

Diagnostic Features	Test small and conical in profile; oral surface concave towards peristome. Very slight anterior inedentation present at ambitus Apical disc tetrabasal with four gonopores but genital plate 2 dominating Ambulacra petaloid aborally. The anterior petal much shorter than the others. Paired petals lanceolate and tending to converge distally; confined to conical part of test Phyllodes not clearly seen but present with inner and oputer series. Pores all double. Peristome large, wider than long and without swollen sides. Only a litltle anterior of centre. Periproct large, in short anal sulcus towards the posterior of the apical surface.
Distribution	Lower Cretaceous (Albian), Brazil
Name gender	masculine
Type	Acriaster sergipensis Smith, in Smith & Bengtson, 1991, p. 47.
Species Included	Only the type species.
Classification and/or Status	Stem group Neognathostomata, Archiaciidae Monotypic.
Remarks	Distinguished from other archiaciids by its aboral periproct and short, petaloid anterior ambulacrum. Smith, A. B. & Bengtson, P. 1991. Cretaceous echinoids from north-eastern Brazil. Fossils and Strata 31, 1-88.