The Echinoid Directory

Plesiodiadema Pomel, 1883, p. 106

[Dermatodiadema A. Agassiz, 1898, p. 76; type species Dermatodiadema globulosum A. Agassiz, 1898]

Diagnostic Features
  • Test small; subglobular; plating fragile but firmly tesselated.
  • Apical disc monocyclic with periproct rim circular.
  • Ambulacra straight and relatively narrow; pore-pairs non-conjugate; uniserial throughout.
  • Ambulacral plating pseudocompound with small primary tubercle on every third plate (other plates without tubercles); all plates extend across the full ambulacral width.
  • Sphaeridial pits extend above ambitus.
  • Interambulacral zone composed of pentagonal plates with a single large primary tubercle.
  • Primary tubercles perforate and crenulate; secondary tuberculation confined to plate margins.
  • Peristome with shallow, rounded buccal notches.
  • Spines slender, and verticillate. Lumen filled with open mesh of horizontal partitions and vertical pillars.
Recent, Indo-Pacific and Atlantic.
Name gender neuter
Aspidodiadema microtuberculatum A. Agassiz, 1879, by original designation.
Species Included
  • P. microtuberculatum A. Agassiz, 1879; Recent.
  • P. indicum (Doderlein, 1900); Recent; Malay archipelago and Indian Ocean.
  • P. globulosum (A. Agassiz, 1879); Recent; west American deep-sea.
  • P. antillarum (A. Agassiz); Recent, central Atlantic and Caribbean.
  • P. horridum (A. Agassiz); Recent, East Pacific.
  • P. molle (Doderlein, 1901); Recent, Indian Ocean.
  • P. amphigymnum (de Meijere, 1902); Recent, Gulf of Boni
Classification and/or Status

Acroechinoidea, Aspidodiadematoida Aspidodiadematidae.



Differs from Aspidodiadema in having much smaller ambulacral tubercles that do not form a single perradial series offset to left and right. It is very similar to the fossil Gymnotiara (especially G. jessopi), differing from that taxon in having fully formed tubercles adapically in its interambulacral zones.

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

Pomel, A. 1883. Classification méthodique et Genera des Échinides vivante et fossiles. Thèses présentées a la Faculté des Sciences de Paris  503, A. Jourdan, Alger, 131 pp.