The Echinoid Directory

Pleiocyphus Pomel, 1883, p. 82

Diagnostic Features
  • Test subglobular, flattened below, gently domed above to flat top.
  • Apical disc moderately large; dicyclic; plates firmly bound to corona and slightly raised forming cap. Genital plates elongate with subcentral gonopore in median depression; ocular plates smaller and not projecting much. Periproct subcircular, rather small. Disc with pustular ornament and sutural depressions.
  • Ambulacra straight; pore-pairs small, uniserial; no differentiation of pore-pairs between apical and oral surfaces. Almost no expansion adorally to form phyllodes.
  • Ambulacral plating trigeminate; with all elements reaching the perradius adapically. Ambital and adoral plates with a large primary tubercle, apical plates with pustules. Plate compounding as in Glypticus.
  • Interambulacral plates wider than tall; with a single large primary tubercle on ambital and oral plates. Above the ambitus plates lacking tubercles but with three or four large, subequal ribbed pustules forming horizontal rows. These pustules also extend adorally in the perradial region of interambulacra.
  • Tubercles imperforate and non-crenulate; mamelons massive on subambital plates.
  • Peristome circular, slightly sunken; buccal notches distinct and rather sharp but shallow and rimmed; no tag.
  • No primibasal interambulacral plate.
  • Sphaeridial arrangement unknown.
  • Spines and lantern unknown.
Distribution Upper Jurassic (Oxfordian), western Europe.
Name gender masculine
Type
Glypticus regularis Etallon, 1858, p. **, by monotypy.
Species Included Only the type species.
Classification and/or Status

Euechinoidea, Echinacea, Arbacioida, Glypticidae.

Presumed monophyletic.

Remarks

Although Pomel (1883) stated that there were true tubercles forming rows on aboral plates, these, on closer inspection, are simply large pustules with fine radial ribs. There are no spine-bearing tubercles of any sort on the aboral surface. Pleiocyphus differs from Glypticus in having an aboral ornament of uniformly circular pustules: ornamentation in Glypticus takes the form of rather elongate bars.

Pomel, A, 1883. Classification methodique et genera des echinides vivants et fossils. Alger, Paris.