The Echinoid Directory

Plesiaster Pomel, 1883, p. 42

Diagnostic Features
  • Test ovate with shallow anterior sulcus; posterior face truncate. Test low domal in profile.
  • Apical disc ethmophract with four gonopores; central.
  • Anterior ambulacrum subpetaloid; sunken.
  • Other ambulacra petaloid aborally and weakly sunken; extending most of the distance to the ambitus in plan view.
  • Petals with smooth, undivided perradial zone.
  • Peristome small and pentagonal; slightly inclined towards anterior; not covered by labrum.
  • Labrum plate longitudinally elongate, extending to amb. plate 2. Sternal plates asymmetric with the labral plate only just reaching sternal plate 2a; post sternal plates alternating.
  • Periproct on posterior truncate face at about mid-height.
  • Subanal fasciole present; ovate; crossing rear of sternal plates 2a and 2b.
  • Traces of fasciole at ends of petals aborally and irregular patches of aligned granules interradially.
Upper Cretaceous (Santonian to Campanian) to Palaeocene, Africa, Madagascar, India, Spain, Turkey.
Name gender masculine
Micraster peini Coquand, 1862, p. 245, by original designation.
Species Included
  • P. peini (Coquand, 1862); Santonian-Campanian, North Africa.
  • P. hourcqi (Lambert, 1933); Campanian-Maastrichtian, Madagascar.
  • P. nobilis (Stoliczka, 1873); Campanian-Maastrichtian, Madagascar, southern India.
  • P. trangahyensis (Lambert, 1936); Maastrichtian, Madagascar.
  • P. amnicus (Greyling, 1996); Maastrichtian, Zululand.
  • P. nicklesi (Collignon & Lambert, 1928); Danian, Spain.
  • ?P. gregalis (Bohm, 1927); Danian, Turkey.
Classification and/or Status

Spatangoida, Micrasterina, Micrasteridae.

Possibly paraphyletic by exclusion of Micraster and its relatives


Differs from Micraster in having anterior ambulacrum subpetaloid aborally, and in having the peristome opening downwards and not obscured by the labral plate. It also has the primitive asymmetric plastron. Differs from Gibbaster in having peristome facing downward and not covered by the labral plate, and in having longer and more bowed petals.

The Maastrichtian species listed above were placed in Mokotibaster by Smith & Jeffery (2000), but the type species of that genus has a very different plastron plating.

Pomel, A. 1883. Classification méthodique et genera des Échinides vivante et fossiles. Thèses présentées a la Faculté des Sciences de Paris pour obtenir le Grade de Docteur ès Sciences Naturelles, 503, 131 pp. Aldolphe Jourdan, Alger.