The Echinoid Directory

Chaetodiadema Mortensen, 1903, p. 1

Diagnostic Features
  • Test flattened; plating rather fragile with imbricate sutures; flexible.
  • Apical disc monocyclic with genital plates projecting interradially. Larger periproctal plates forming a peripheral zone.
  • Ambulacra narrow and straight; pore-pairs non-conjugate; uniserial; becoming widely spaced adorally.
  • Ambulacral plating trigeminate at ambitus with single large primary tubercle per plate. Simple on oral surface.
  • Interambulacral zone wide, with ambital plates distinctly wider than tall and carrying multiple subequal tubercles Adapical plates virtually naked.
  • Primary tubercles perforate and crenulate.
  • Over most of the oral surface tuberculation reduced to a fine dense granulation.
  • Peristome small and somewhat sunken; buccal notches small and rounded.
  • Spines long and slender; flattened; central lumen filled with coarse open mesh; with verticillate ornament.
Recent, Indo-Pacific.
Name gender neuter
Chaetodiadema granulatum Mortensen, 1903, by original designation.
Species Included
  • C. granulatum Mortensen, 1903; Recent, Indo-West Pacific.
  • C. pallidum Agassiz & Clark 1907; Recent, Hawaii.
  • C. keiense Mortensen, 1939; Recent, Kei Islands.
  • C. japonicum Mortensen, 1904; Recent, Japan.
  • C. africanum H. L. Clark, 1924; Recent, South Africa.
  • C. tuberculatum H. L. Clark, 1909; Recent, South Australia.
Classification and/or Status

Diadematoida; Diadematidae.

Presumed monophyletic.


Differs from Diadema and most diadematoids in having simple plating and dense granulation adorally instead of differentiated primary and secondary tubercles. It comes closest to Eremopyga but in that taxon ambulacral plating remains compound adorally.

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