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.
Distribution	Recent; Japan.
Name gender	masculine
Type	Toxocidaris depressa A. Agassiz, 1863, by original designation.
Species Included	Only the type species.
Classification and/or Status	Euechinoida, Echinoida, Strongylocentrotidae Monotypic.
Remarks	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