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The Echinoid Directory

Schizocosmus Markov, 1990, p. 54

Diagnostic Features
  • Test ovate with faint trace of anterior sulcus at ambitus; posterior face weakly truncate.
  • Apical disc ethmolytic with three gonopores; central.
  • Anterior ambulacrum slightly sunken adapically; pore-pairs uniserial and tube-feet not strongly developed.
  • Petals of subequal length; parallel-sided and sunken; deeply so in the females.
  • Peristome kidney-shaped, facing forward into frontal groove. Labrum projecting to cover peristome in oral view.
  • Labral plate extending to the third ambulacral plate; only a little shorter than sternal plates. Episternal plates not forming part of flat plastronal surface.
  • Periproct on posterior truncate face. Subanal tube feet scarcely penicillate.
  • Marginal fasciole present; passing two or three plates below the ends of the anterior petals. Peripetalous fasciole indented behind anterior petals by one interambulacral plate and absent anteriorly. The two fascioles remain separate to the anterior interambulacrum where they may become coalesced.
Distribution
Recent, Antarctic and subantarctic.
Name gender masculine
Type
Pericosmus abatoides Clark, 1925, p. 199, by original designation.
Species Included
  • P. abatoides (Clark, 1925); Recent, Antarctic.
Classification and/or Status

Spatangoida, Paleopneustina, Incertae sedis A.

Monotypic.
Remarks

De Ridder et al. (1992) discuss the type species and give a plating diagram. Markov & Solovjev (2001) provide a detailed comparison of the genus. It differs from Tripylus in having the marginal and peripetalous fascioles separate below the anterior petals and in having a considerably larger and longer labral plate.

Mortensen, T. 1951. A monograph of the Echinoidea V. Spatangoida 2. C. A. Reitzel, Copenhagen.

De Ridder, C., David, B., & Larrain, A. 1992. Antarctic and Subantarctic echinoids from 'Marion Dufresne' expeditions MD03, MD04, MD08 and from the 'Polarstern' expedition Epos III. Bulletin du Musee national d'Histoire naturelle, Paris 4e serie 14, 405-441.

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