The Echinoid Directory

Seunaster Lambert, in Blayac, 1912, p. 385

[=Synochitis Lambert, 1917, p. 30 (objective)]

Diagnostic Features
  • Test cordate with shallow anterior sulcus on aboral surface, becoming much deeper at ambitus and adorally. Lower surface apparently flat, upper surface weakly conical.
  • Apical disc somewhat anterior of centre with four gonopores.
  • Paired ambulacra non-petaloid; pore-pairs rudimentary. Ambulacral plates numerous and much wider than tall over aboral surface.
  • Peristome small and oval; near anterior border and facing down.
  • Plastron plating orthosternous - labral plate followed by single symmetrical sternal plate, then a pair of near symmetric episternals.
  • Plastron plating continuous.
  • Enlarged primary tubercles apparently absent aborally, but most specimens without outer surface of plates preserved..
  • ?No fascioles.
Distribution
Upper Cretaceous (Maastrichtian), Europe, North Africa, Middle East, Ukraine, Kazachstan.
Name gender masculine
Type
Holaster bouillei Cotteau, in de Bouille, 1873, p. 24, by original designation.
Species Included
  • S. altus (Cotteau, 1873); Maastrichtian, Europe, North Africa, Turkey, Ukraine, Kazachstan.
  • S. heberti (Seunes, 1889); Maastrichtian, Europe, Turkey, North Africa, Georgia, Caucasus.
  • S. bouillei (Seunes, 1889); Maastrichtian, Europe, Turkey.
  • S. gauthieri (Lambert, 1896); late Cretaceous, Madagascar.
Classification and/or Status

Holasteroida, Meridosternata, Stegasterina, Stegasteridae.

Monophyletic.

Remarks

Identical to Entomaster in all plating details but differing from that genus in lacking major tubercles over the aboral surface. Tholaster differs in having a deep anterior sulcus from the apex and in having prominent large primary tubercles.

A. B. Smith, J. Gallemi. C. H. Jeffery, G. Ernst & P. D. Ward 1999. Late Cretaceous-early Tertiary echinoids from northern Spain: implications for the Cretaceous-Tertiary extinction event. Bulletin of the Natural History Museum, London (Geology Series) 55, 81-137.