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The Echinoid Directory

Pseudogibbaster Moskvin, 1983, p. 111

Diagnostic Features
  • Test ovate with shallow anterior sulcus; posterior face truncate. Test low domal to subconical in profile. Often highly inflated.
  • Apical disc ethmophract with four gonopores; central.
  • Anterior ambulacrum sunken aborally, with widened adapical pore-pairs.
  • Other ambulacra petaloid aborally and weakly sunken; extending only part 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. Sternal plates asymmetric with oblique median suture.
  • Periproct on posterior truncate face at about mid-height.
  • Subanal fasciole present.
  • Traces of fasciole at ends of petals aborally.
Distribution
Palaeocene, Spain, Ukraine, Kazakhstan.
Name gender masculine
Type
Protobrissus akkajensis Moskvin & Poslavskaya, 1959, p. 290, by original designation.
Species Included
  • P. akkajensis (Moskvin & Poslavskaya, 1959); Danian, Spain to Kazakhstan.
  • P. tercensis (Cotteau, 1877); Palaeocene, Spain, Ukraine, Caucasus.
  • P. depressus Kongiel, 1937; Palaeocene, Poland, Ukraine, Caucasus.
Classification and/or Status

Spatangoida, Micrasterina, Micrasteridae.
Remarks

Differs from Micraster in having pore-pairs in the frontal ambulacrum subpetaloid, a more inflated shape, and a non-labiate peristome. Differs from Plesiaster in having shorter and narrower petals and a more inflated outline. However, differences are minor and there are no structural plating differences between these taxa. Closest to Gibbaster in appearance differing only in minor details (Pseudogibbaster has a more downward-facing peristome and less projecting labral plate, and its periproct opens higher on the posterior surface). Possibly only a subgenus of Gibbaster.

Smith, A. B. & Jeffery, C. H. 2000. Maastrichtian and Palaeocene echinoids: a key to world faunas. Special Papers in Palaeontology 63, 1-404.

Smith, A. B., Gallemi, J., Jeffery, C. H., Ernst, G. & Ward, P. D. 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.