The Echinoid Directory

Corystus Pomel, 1883, p. 61

[=Galeraster Cotteau, 1890, p. 548, type species G. australiae Cotteau, 1890 (=Rhynchopygus dysasteroides Duncan, 1877); = Duncaniaster Lambert, 1896, p. 317, type species Holaster australiae Duncan, 1877; =Stereopneustes de Meijere, 1902, type species S. relictus de Meijere, 1902 ]

Diagnostic Features
  • Test ovate with anterior ambulacrum convex to faintly concave at ambitus; posterior face truncate.
  • Apical disc with four gonopores. Hydropores confined to genital plate 2.
  • Ambulacra flush; pore-pairs of paired ambulacra composed of similar-sized pores set in conjugate groove.
  • Pore-pairs of anterior ambulacrum smaller and less developed than those in other ambulacra.
  • Peristome a little anterior of centre; ovate and depressed.
  • Plastron plating orthosternous with labral plate followed by a single large sternal plate then a pair of small, symmetical episternal plates and a single rostral plate.
  • Periproct marginal, on vertically truncate face.
  • Aboral tuberculation fine and homogeneous with weakly sunken tubercles set in a dense groundmass of fine granules.
  • Subanal fasciole present encircling the rostral plate.
Distribution
Late Middle or early Late Eocene to Recent of Australia, New Zealand and China Sea.
Name gender masculine
Type
Rhynchopygus dysasteroides Duncan, 1877, p. 49, by original designation.
Species Included
  • C. dysasteroides (Duncan, 1877); Oligocene and Lower Miocene of Australia and New Zealand.
  • C. australiae (Duncan, 1877); Late Middle or early Late Eocene, Australia.
  • C. relictus (de Meijere, 1902); Recent, China Sea.
Classification and/or Status

Holasteroida; Meridosternata, Urechinina, Corystusidae.

Monophyletic.

Remarks

Differs from Huttonechinus in lacking a distinct adoral groove leading to the peristome, and in having a narrower plastron and meridoplacous plating in the lateral interambulacra adorally. Cardabia is very similar, but has rudimentary aboral pore-pairs. Basseaster differs in lacking a rostral plate and its posterior ocular plates are separated from the remaining apical discs.

The nomenclatural history of this taxon is complicated and was clarified by Foster & Philip (1976a). Detailed biometric analyses of populations from different stratigraphic levels has been carried out by Forster & Philip (1976b).

Foster, R. J. & Philip, G. M. 1976a. Corystus dysasteroides, a Tertiary holasteroid echinoid formerly known as Duncaniaster australiae. Transactions of the Royal Society of South Australia 100, 113-116.

Foster, R. J. & Philip, G. M. 1976b Statistical analysis of the Tertiary holasteroid Corystus dysasteroides from Australia. Thalassia Jugoslavica 12, 129-144.

Pomel, A. 1883. Classification méthodique et genera des Échinides vivante et fossiles. Thèses présentées a la Faculté des Sciences de Paris pour obtenir le Grade de Docteur ès Sciences Naturelles, 503, 131 pp. Aldolphe Jourdan, Alger.