The Echinoid Directory

Psephoaster McNamara, 1987, p. 347

Diagnostic Features
  • Test subglobular without anterior sulcus.
  • Apical disc ethmophract with four gonopores; central.
  • Anterior ambulacrum narrow and not sunken adapically. Pore-pairs small and oblique, with adapical pore-pairs differentiated from ambital pores.
  • Petals narrow and weakly sunken; parallel; anterior petals longer than posterior petals.
  • Peristome kidney-shaped to ovate, with raised rim.
  • Labral plate longer than wide; extending to second ambulacral plate. Sternal plates triangular and symmetric; expanding to posterior.
  • Periproct small and high on posterior truncate face.
  • Peripetalous fasciole present; not indented behind anterior petals.
  • Aboral tuberculation fine, dense and uniform; not sunken.
Eocene to Miocene, Australia.
Name gender masculine
Psephoaster klydonos McNamara, 1987, p. 350, by original designation.
Species Included
  • P. lissos McNamara, 1987; Upper Eocene, South Australia.
  • P. apokryphos McNamara, 1987; Upper Oligocene, Australia.
  • P. klydonos McNamara, 1987; Lower Miocene, South Australia.
Classification and/or Status

Spatangoida, Hemiasterina, Hemiasteridae.

Monophyletic; subjective junior synonym of Bolbaster.


McNamara distinguished this taxon from Hemiaster because of its flush anterior ambulacrum and its narrow, poorly developed and only slightly depressed petals. In addition it has a shorter labrum, extending to ambulacral plate 2, and symmetrical sternal plates. In all of these features it resembles Bolbaster and is here treated as a synonym.

Neraudeau (1994) distinguished Psephoaster from Bolbaster stating that the anterior part of the petals in Psephoaster have atrophied pore-pairs. This is, however, a character developed in almost all hemiasterids to a greater or lesser extent.

McNamara, K. J. 1987. Taxonomy, evolution, and functional morphology of southern Australian Tertiary hemiasterid echinoids. Palaeontology 30, 319-352.

Neraudeau, D. 1994. Hemiasterid echinoids (Echinodermata: Spatangoida) from the Cretaceous Tethys to the present-day Mediterranean. Palaeogeography, Palaeoclimatology, Palaeoecology 110, 319-344.