The Echinoid Directory

Goniodiadema Mortensen, 1939, p. 549

Diagnostic Features
  • Test inflated and pentagonal in outline; plating rather fragile and slightly flexible.
  • Apical disc hemicyclic with posterior oculars insert; periproct large and without distinct plates.
  • Ambulacra narrow and straight; pore-pairs non-conjugate. Uniserial and in triads at ambitus and aborally but more irregular and widely spaced adorally.
  • Ambulacral plating trigeminate at ambitus large primary tubercles variably developed - not forming a strict biseries. Adoral ambulacra with irregular scattering of dense granulation, but distinct primary tubercles.
  • Interambulacral zone wide, with ambital plates distinctly wider than tall.
  • Up to eight primary tubercles on ambital plates; all tubercles perforate and crenulate.
  • Aboral surface almost naked; oral surface highly granular.
  • Peristome relatively small.
  • Spines long and slender (at least diameter of test); hollow, with verticillate ornament.
Recent, Mauritius.
Name gender neuter
Goniodiadema mauritiense Mortensen, 1939, by original designation.
Species Included
  • Only the type species.
Classification and/or Status

Diadematoida; Diadematidae.



Differs from Chaetodiadema in having a pentagonal test outline, with the angles of the pentagon interradial and in having compound triads with primary tubercles clearly continuing to the peristome. It is extremely similar to Eremopyga Agassiz & Clark, and possibly should be synonymized.

Mortensen, T. 1940. A monograph of the Echinoidea. Volume III. 1, Aulodonta. C.A. Reitzel, Copenhagen