The Echinoid Directory

Eopericosmus Markov & Solovjev, 2001 p. 16, 81

Diagnostic Features
  • Test cordate with shallow frontal sulcus from apex to peristome. Depressed in profile with rounded ambitus.
  • Apical disc ethmolytic (posterior oculars may just meet in some individuals), with 4 gonopores; positioned anterior of centre.
  • Anterior ambulacrum narrow and weakly sunken adapically. Pore-pairs uniserial and small adapically.
  • Other ambulacra petaloid; petals short, parallel-sided and weakly sunken; paired pores continue for a few plates beyond the peripetalous fasciole. Anterior petals widely divergent, about same length as posterior petals.
  • Pore-pairs continue beyond the end of the petals; no occluded plates.
  • Periproct on posterior face; oral side framed by plates 5a/b.
  • Peristome D-shaped; facing obliquely downwards.
  • Labral plate squat and extending to second amb plate. Sternal plates large with offset sutures to rear; episternal plates biserially offset.
  • Interambulacrum 1 generally amphiplacous.
  • No primary tubercles differentiated.
  • Peripetalous fasciole incomplete; absent anteriorly in amb III and Iamb 2b and 3a; merged with marginal fasciole just anterior of the anterior petals. Marginal fasciole present.
Distribution
Palaeocene to Oligocene, Mangyshlak and New Zealand.
Name gender masculine
Type
Eopericosmus typicus Markov & Solovjev, 2001, p. 16, 82, by original designation.
Species Included
  • ?E. altus (Hutton, 1873); Oligocene, New Zealand.
  • E. typicus Markov & Solovjev 2001; Lower Palaeocene (Danian) Mangyshlak.
  • E. sveshnikovi Markov & Solovjev 2001; Palaeocene (Montian), Mangyshlak.
Classification and/or Status

Spatangoida, Paleopneustina, Incertae sedis A.

Probably paraphyletic (by exclusion of Pericosmus and Kertaster).

Remarks

Differs from Pericosmus in having four gonopores and in having the peripetalous and marginal fascioles merged in the anterior interambulacrum. The reference of the New Zealand species to this taxon is questionable.

Markov, A. V. & Solovjev, A. N. 2001. Echinoids of the family Paleopneustidae (Echinoidea, Spatangoida): morphology, taxonomy, phylogeny. Geos 2001, 1-109.