The Echinoid Directory

Isopatagus Mortensen, 1948, p. 113

Diagnostic Features
  • Test ovate without anterior sulcus; tapering posteriorly. Test domed in profile.
  • Apical disc subcentral; ethmophract with three gonopores (no gonopore in genital plate 2).
  • Ambulacra all similar; all five ambulacra forming short, feebly depressed petals aborally.
  • Petals with smooth, narrow, undivided perradial zone; open distally and ending gradually. Pore-pairs conjugate.
  • Peristome D-shaped and facing downwards. Surrounded by a distinct rim.
  • Labral plate longitudinally elongate, flask-shaped; extending to third ambulacral plate. Sternal plates paired and symmetrical; episternal plates biserially offset and not indented to rear by ambulacral plates.
  • Periproct on short posterior truncate face; well below mid-height in posterior view; just inframarginal.
  • No fascioles.
  • Aboral tuberculation of small tubercles set in a groundmass of granules.
Recent, West Pacific; 890 m.
Name gender masculine
Isopatagus obovatus, Mortensen, 1948 p. 113, by original designation.
Species Included
  • Only the type species.
Classification and/or Status

Spatangoida, Micrasterina, Micrasteridae, Cyclasterinae.



Mortensen (1950) recognized that this taxon was close to Isaster, but distinguished it as having pore-pairs remaining distinct outside the petals even to the ambitus.

Mortensen, T. 1950. A monograph of the Echinoidea. V. Spatangoida 1. C. A. Reitzel, Copenhagen.