The Echinoid Directory

Pseudocentrotus Mortensen, 1903, p. 122

Diagnostic Features
  • Test large and depressed; oral surface flat.
  • Apical disc hemicyclic.
  • Ambulacral plating polygeminate with 6 or 7 pore-pairs to a compound plate at ambitus and above, but fewer and more crowded adorally.
  • Oral surface completely flat with relatively small peristome and wide highly developed phyllodes.
  • Pore-pairs forming strongly oblique lines on each plate.
  • A single primary ambulacral tubercle to each plate.
  • Interambulacral plates with primary tubercle and large secondary tubercles, not forming horizontal rows.
  • No naked zones aborally.
  • Buccal notches shallow, but with prominent tags.
  • Auricles fused perradially.
Recent; Japan.
Name gender masculine
Toxocidaris depressa A. Agassiz, 1863, by original designation.
Species Included
Only the type species.
Classification and/or Status
Euechinoida, Echinoida, Strongylocentrotidae


Easily distinguished from other toxopneustids by its subhorizontal arcs of pore-pairs some 6 or 7 to a plate. Biochemical work has shown that this taxon is closer to strongylocentrotids (N. Matsuoka 1987 Zoological Science 4, 339-347) and its ambulacral structure suggests sister group relationships with Hemicentrotus which differs in having rather less pronounced buccal notches without the tags.

Mortensen, T. 1903. The Danish Ingolf-Expedition 1895-1896. Vol. 4, No. 2. Echinoidea, pt. 1.Copenhagen, 198 pp.

Mortensen, T. (1943) A monograph of the Echinoidea Part III.2, Camarodonta 1. C. A. Reitzel, Copenhagen