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The Echinoid Directory

Family Pericosmidae Lambert, 1905, p. 153

Diagnosis	Paleopneustinid spatangoids with: thick-shelled test with frontal groove; apical disc with three gonopores (no gonopore in genital plate 2); ambulacrum III pores differentiated, associated with suckered tube-feet; paired ambulacra petaloid; petals short, narrow, parallel-sided and with occluded plates at end; peristome with projecting labral plate and well developed but short phyllodes; labral plate stout and longitudinally elongate; extending to second ambulacral plate. Sternal plates long and symmetrical. Episternal plates biserially offset; not indented to rear by ambulacral plates; periproct large and marginal; bounded by interambulacral plates 5a/b on oral side; marginal and peripetalous fascioles present.
Range	Palaeocene to Recent; widespread.
Remarks	Distinguished from the Paleopneustidae by the rather short, sunken petals, well developed frontal groove and suckered tube-feet. Stem group Protenastridae have no occluded plates at the ends of their petals and their marginal and peripetalous fascioles are often coalesced in the anterior interambulacra.

Diagnosis

Paleopneustinid spatangoids with:

thick-shelled test with frontal groove;
apical disc with three gonopores (no gonopore in genital plate 2);
ambulacrum III pores differentiated, associated with suckered tube-feet;
paired ambulacra petaloid; petals short, narrow, parallel-sided and with occluded plates at end;
peristome with projecting labral plate and well developed but short phyllodes;
labral plate stout and longitudinally elongate; extending to second ambulacral plate. Sternal plates long and symmetrical. Episternal plates biserially offset; not indented to rear by ambulacral plates;
periproct large and marginal; bounded by interambulacral plates 5a/b on oral side;
marginal and peripetalous fascioles present.

Range

Palaeocene to Recent; widespread.

Remarks

Distinguished from the Paleopneustidae by the rather short, sunken petals, well developed frontal groove and suckered tube-feet. Stem group Protenastridae have no occluded plates at the ends of their petals and their marginal and peripetalous fascioles are often coalesced in the anterior interambulacra.