The Echinoid Directory

Prymnaster Koehler, 1914, p. 187

Diagnostic Features	Test ovate with broad, shallow anterior sulcus; slightly pointed to rear. Apical disc ethmolytic, with 4 gonopores; subcentral. Anterior ambulacrum weakly sunken aborally, forming only a modest notch at the ambitus; pore-pairs and tube-feet specialized; uniserially arranged. Other ambulacra petaloid and deeply sunken, anterior petals only slightly longer than the posterior petals; petals cruciform and not particularly strongly flexed. Periproct near top of vertical truncate face, with small overhanging beak. Peristome large and kidney-shaped; labral plate not strongly projecting, so peristome downward-facing. Labral plate short and wide; not extending beyond first amb. plate; in broad contact with sternal plates. Sternal plates large and symmetrical; forming the plastron; episternal plates offset and at base of posterior face. Aboral tuberculation fine, uniform and dense. Oral tubercles also dense and uniform. Well-developed peripetalous and latero-anal fascioles. Subanal penicillate tube-feet present.
Distribution	Recent, Indian Ocean. Shallow water silts and muds - infaunal.
Name gender	masculine
Type	Prymnaster angulatus Koehler, 1914, p. 188, by original designation.
Species Included	P. angulatus Koehler, 1914; Recent, Arabian Sea. P. investigatoris Koehler, 1914; Recent, West Indian Ocean.
Classification and/or Status	Spatangoida, Paleopneustina, Schizasteridae ?Subjective synonym of Schizaster
Remarks	Like Schizaster, differing in having less flexed petals that are more deeply sunken and subequal in length. Resembling Abatus but differing in having four gonopores and a latero-anal fasciole in adults. Note that the type species is based on a small individual (20 mm) with poorly developed gonopores. Koehler, R. 1914. Echinoderma of the Indian Museum, VIII, Echinoidea (i) Spatangides. Echinides du Musee Indien a Calcutta; 257 pp., 20 pls.