The Echinoid Directory

Brachysternaster Larrain, 1985, p. 121

Diagnostic Features
  • Test ovate without anterior sulcus; posterior rounded. Test low domed in profile with flat base. Thin-shelled.
  • Apical disc ethmolytic with three gonopores (no gonopore in genital plate 2); central.
  • Strong sexual dimorphism, with females having sunken paired ambulacra for brooding (a male with flush petals is illustrated here).
  • Ambulacrum III narrow with simple pore-pairs aborally; faintly depressed.
  • Paired ambulacra subpetaloid; pore-pairs small and poorly differentiated; petals weakly bowed; without occluded plates at end; open distally.
  • Peristome facing forward and largely hidden by projecting labrum in oral view; perioral area sunken.
  • Phyllodes very well developed; up to 9 lateral pores and 6 anterior pores per column; pores single.
  • Labral plate peg-shaped, relatively short and broad; extending to ambulacral plate 4. Labral plate contiguous in juveniles, but separated from sternal plates by up to two ambulacral plates in adults. Sternal plates extending to amb plate 6; flared posteriorly. Paired episternals biserially offset and very wide; not indented by ambulacral zones.
  • Posterior ambulacra on oral surface naked.
  • Periproct inframarginal; circular and flush; bound by Iamb plates 3a/b orally.
  • No fascioles.
  • Aboral surface with small, scattered primary tubercles.
  • Labral area densely granular. On plastron largest tubercles positioned laterally.
Distribution
Recent, Antarctic.
Name gender masculine
Type
Brachysternaster chesheri Larrain, 1985, p. 121, by original designation.
Species Included
  • Only the type species.
Classification and/or Status

Spatangoida, Paleostomatina, Incertae sedis B.

Monotypic.

Remarks

Distinguished from Amphipneustes, Heterobrissus and other palaeopneustids by its disjunct plastron and by having the episternal plates (5.a.3/5.b.3) bounding the oral side of the periproct (in all other taxa the periproct is bounded by post-episternal plates).

Larrain, A. P. 1985. Brachysternaster, new genus, and Brachysternaster chesheri, new species, of Antarctic echinoid (Spatangoida, Schizasteridae). Polar Research 4, 121-124.