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.
Upper Cretaceous (Maastrichtian), Europe, North Africa, Middle East, Ukraine, Kazachstan.
Name gender masculine
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.



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.