The Echinoid Directory

Psephechinus Pomel, 1883, p. 81

[=Sporadocyphus Pomel, 1883, p. 81, type species Polycyphus jauberti Cotteau, 1863 ]

Diagnostic Features
  • Test domed, flattened below.
  • Apical disc small, subcircular; dicyclic with genital plates a little wider than tall. G2 enlarged compared to others. Oculars small. Periproct subcircular. A few sacattered tubercles on genital plates.
  • Ambulacra trigeminate with pore-pairs in strong arcs forming adradial band throughout. Plate compounding diadematid, with upper and lower elements smaller but reaching the perradius. Distinctly widening adorally.
  • Ambulacral plates with two subequal tubercles on ambital and adoral plates; the inner series becoming smaller and lost adapically.
  • Interambulacral plates much wider than tall. Up to 6 subequal tubercles forming a row on ambital plates, reduced to single tubercle close to apical disc.
  • Ambulacral and interambulacral tubercles of similar size; neither increase in size below ambitus significantly.
  • No aboral naked interradial zone.
  • Primary tubercles imperforate and non-crenulate.
  • Peristome large, weakly sunken; buccal notches deep and sharp.
  • Spines and lantern unknown; no primordial interambulacral plate.
Middle Jurassic, western Europe.
Name gender masculine
Stomechinus michelini Cotteau, in Cotteau & Triger, 1857, p. 31, by monotypy
Species Included
  • P. michelini (Cotteau, 1857); Bathonian, Europe, North Africa.
  • P. quoniami Gauthier; Bajocian, Morroco [includes P. daguini Lambert, 1933]
  • P. deslongchamsii (Wright, 1854), Bajocian, West Europe [includes Stomechinus sulcatus Cotteau, 1884]
  • P. distinctus (Agassiz); Oxfordian. France
  • P. jauberti (Cotteau, 1863); Bathonian, France
  • P. morieri Cotteau, 1880; Bathonian, France
  • P. schlumbergi Cotteau, 1864; Bathonian, France
Classification and/or Status

Euechinoidea, Echinacea, Stomechinidae.


Like Polycyphus in having a primary tubercle developed on each ambulacral triad but with tubercles not clearly organized into vertical columns above the ambitus and with a less pronounced change in the size of tubercles at the ambitus.  Stomechinus has primary tubercles developed on every second ambulacral plate for the most part.

Pomel, A. 1883. Classification methodique et genera des echinides vivante et fossiles. Thesis presentes a l'Academie des Sciences de Paris. Alger, A. Jourdan.