The Echinoid Directory

Tholaster Seunes, 1891, p. 23

[=Gibbaster Seunes, 1889, p. 819, non Gauthier, 1887]

Diagnostic Features
  • Test cordate, longer than wide with deep anterior sulcus. Lower surface apparently flat; upper surface low domal.
  • Apical disc subcentral with four gonopores.
  • Paired ambulacra non-petaloid; pore-pairs rudimentary. Ambulacral plates relatively tall over aboral surface.
  • Frontal groove present from apex; deepening towards ambitus and continuing adorally to peristome as sharply-defined groove.
  • Peristome small and oval, facing anteriorly into groove.
  • Plastron plating meridosternous - labral plate followed by single symmetrical sternal plate, subsequent plating biserial.
  • Periproct supramarginal on steeply sloping posterior face surface.
  • Enlarged primary tubercles prominent on outer column of interambulacral plates in interambs 2 and 3. Large primary tubercles also developed adapically in other interambulacral zones.
  • ?No fascioles.
Distribution
Upper Cretaceous (Maastrichtian), French and Spanish Pyrenees.
Name gender masculine
Type
Gibbaster munieri Seunes, 1889, p. 819, by original designation.
Species Included
  • Only the type species.
Classification and/or Status

Holasteroida, Meridosternata, Stegasterina, Stegasteridae.

Monotypic.

Remarks

Differs from Seunaster in having the frontal ambulacrum depressed adapically, and in the prominent large primary tubercles that are developed aborally in interambulacral zones. Differs from Opisopneustes in plastron structure and in lacking petals. Differs from Stegaster and Entomaster in lacking petals. Differs from Guettaria in lacking supplementary gonopores in the ocular plates, in tuberculation pattern and in lacking paired episternal plates.

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.

Seunes, J. 1891. Echinides Cretaces des Pyrenees Occidentales. Bulletinde de la Societe geologique de France, Serie 3, 19, p. 23-33, pls 1-4.