The Echinoid Directory

Contributed by Andrew Smith, November 2011

Eoglyptocidaris Nisiyama, 1966, p. 195

Diagnostic Features
  • Test low and thin.
  • Apical disc and upper surface unknown.
  • Ambulacral plates composed of five elements, with glyptocidaris-style compounding (i.e., formed of a unit of two elements and a unit of three elements with echinid style compounding and united by a primary tubercle).  Pore zones narrow with pore-pairs more or less uniserially arranged.
  • Interambulacral plates rather tall. Primary tubercles dominating the plate and with confluent areoles in each vertical series.  Small secondary tubercles present on ambital plates on both adradial and interradial sides.
  • Peristome relatively small, with broad shallow buccal notches.
  • Spines unknown; lantrn with keeled teeth.
Distribution Oligocene? (possibly Eocene), Japan
Type Glyptocidaris (Eoglyptocidaris) arctina Nisiyama 1966, p. 196, by original designation.
Species Included Only the type species.
Classification and/or Status Carinacea, Stomopneustoida, Glyptocidaridae

Treated as a junior subjective synonym of Glyptocidaris.
Remarks Very close to Glyptocidaris but supposedly differs from that genus "by the structure of ambulacral plates and by the tuberculation on interambulacral plates".  In reality the plate compounding illustrated by Nisiyama (1966, fig. 7) is identical to that shown by Mortensen for adapical plates of G. crenularis, and little distinguishes the tuberculation pattern.

Nisiyama, S. 1966. The echinoid fauna from Japan and adjacent regions. Part 1. Palaeontological Society of Japan Special Papers 11, 1-277, pls 1-18.