The Echinoid Directory

Subfamily Palaeostominae Loven, 1868, p. 432


 Hemiasterid spatangoids with:

  • apical disc ethmolytic with two gonopores (gonopores absent from anterior genital plates);
  • labral plate elongate, extending to second or third ambulacral plate;
  • sternal plates symmetrical; episternal plates offset;
  • peripetalous fasciole present; indented by one plate behind the anterior petals;
  • anterior interambulacra amphiplacous, lateral interambulacra meridosternous;
  • ambulacral zones not strongly pinched as they cross the peripetalous fasciole.
Eocene to Recent; worldwide.

Mortensen (1950) included only Palaeostoma in the family Palaeostomidae, remarking on the uniqueness of its pentagonal peristome and five triangular plates covering the opening. Ditremaster has a similar pentagonal peristome as juveniles and a similar ethmolytic apical disc with only two gonopores. Both genera further differ from hemiasterids by having the peripetalous fasciole indented by a single interambulacral plate behind the anterior petals. One other genus, Sarsiaster, is also included, based on its similar apical disc and peripetalous fasicole pattern, even though it has a kidney-shaped peristome.

The taxon is treated as a subfamily of Hemiasteridae.

Trachyaster has an ethmolytic apical disc and may belong here, although it retains four gonopores.

Loven, S. 1868. Om Leskia mirabilis Gray. Ofversigt af Kongelige Vetenskaps-Akademiens, Forhandlingar 24 (1867), 431-440.