The Echinoid Directory

Orthaster Moskvin, 1982, p. 103

Diagnostic Features
  • Test ovate with shallow anterior sulcus; posterior face obliquely truncate. Test inflated in profile.
  • Apical disc ethmophract with three gonopores; genital plate 4 without gonopore; positioned a little anterior of centre.
  • Ambulacra all similar; flush. Pore-pairs in anterior ambulacrum smaller and more oblique than those in paired ambulacra which are subpetaloid adapically.
  • Peristome small and circular; at anterior border and facing forward in type species but on lower surface and more downward-facing in other species.
  • Labrum highly elongate; as long as the sternal plates; extending to posterior of ambulacral plate 2. Sternal plates narrow and symmetric. Episternal plates biserially offset. Adjacent ambulacral zones not indenting the plastron.
  • Periproct small and circular, towards top of posterior face.
  • Peripetalous fasciole present; passing high up behind the apical disc and dropping steeply to pass ambitally around the anterior.
  • Tubercles small, uniform, weakly sunken.
Distribution
Upper Cretaceous (Campanian) to Palaeocene (Thanetian), Europe, former Soviet Union to Dagestan.
Name gender masculine
Type
Orthaster dagestanensis Moskvin, 1982 p. 103, by original designation.
Species Included
  • O. dagestanensis Moskvin, 1982; Palaeocene, Ukraine, Kazakhstan, Dagestan.
  • O. alievi Moskvin, 1982; Campanian-Maastrichtian, Dagestan, Kopet Dag, Caucasus.
  • Orthaster sp. Kroh, 2001; Danian, Austria
Classification and/or Status

Spatangoida, Hemiasterina, Aeropsidae.

Monophyletic? (The difference between this taxon and Coraster hinge solely on the numberof gonopores present. Further work may show that this is not astable character on which to base a generic division).

Remarks

Differs from Cottreaucorys in having no well developed subanal heel and (for the type species) in having the peristome much closer to the anterior border and more or less vertical. Differs from Coraster in having 3 gonopores, not 4, but is otherwise extremely similar. Homoeaster is more subpyramidal in profile and has lower more densely packed ambulacral plates adapically, with the peristome further removed from the anterior border.

Smith, A. B. and Jeffery, C. H. 2000. Maastrichtian and Palaeocene echinoids: a key to world faunas. Special Papers in Palaeontology 63, 1-406.

Kroh, A. 2001. Echinoids from the Danian (Lower Paleocene) Bruderndorf Formation of Austria. Osterreichische Akademie der Wissenschaften Schriftenreihe der Erdwissenschaftlichen Kommissionen 14, 377-463.