The Echinoid Directory

Thrichodiadema A. Agassiz, 1863, p. 354

[=Trichodiadema Duncan, 1889, p. 294 (nomen vanum)]

Diagnostic Features
  • Test plating rather fragile, although plating effectively sutured throughout (adapical interradial suture weakly flexible).
  • Apical disc small and hemicyclic with ocular plates II and III not in contact with periproct. Large circular periproct; genital plates not projecting strongly.
  • Ambulacral narrow and straight; pore-pairs non-conjugate, in triads forming three distinct longitudinal series in large individuals.
  • Ambulacral plating trigeminate with single large primary tubercle per plate at ambitus but tending to be on every other plate adorally, especially in larger individuals.
  • Interambulacral plates only a little wider than tall.
  • Single primary tubercle on interambulacral plates; adapical tubercles largest. On ambital plates there are enlarged secondary tubercles on either side; all tubercles perforate and crenulate.
  • Peristome much larger than apical disc, with deep, rounded buccal notches associated with adradial tags.
  • Spines very long and slender; hollow, with verticillate ornament.
Distribution
Recent; Australia and New Zealand regions.
Name gender neuter
Type
Trichodiadema rodgersii A. Agassiz, 1863, by original designation.
Species Included
  • Only the type species.
Classification and/or Status

Diadematoida; Diadematidae.

Subjective junior synonym of Centrostephanus Peters, 1855.

Remarks

Differs from C. longispina, the type of Centrostephanus in having better developed secondary tubercles on interambulacral plates and in having more irregular ambulacral primary tubercles. However, it is also a much larger species and smaller individuals (as illustrated here) lack these characters. See Mortensen (1940, p. 299)

Agassiz, A. 1863. Synopsis of the Echini collected by W. Stimpson, on the North Pacific Exploring Expedition. Proceedings of the Academy of Natural Sciences, Philadelphia 15, 352-361.

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