The Echinoid Directory

Acrosaster Lambert, 1911, p. 30

Diagnostic Features
  • Test small (ca 10 mm diameter), flattened below and domed above to flat-topped apical disc.
  • Apical disc dicyclic; sexually dimorphic. In (?)males genital plates pentagonal, depressed towards periproct; with gonopores towards centre of plate; ocular plates smaller, and not projecting. In (?)female genital plates projecting interradially towards ambitus interradially with gonopore at tip and opening into a narrow, smooth interradial channel in the interambulacra. All plates covered in uniform granulation.
  • Relatively small subcentral periproct that is slightly angular.
  • Ambulacra straight, expanding to ambitus; aboral pore-pairs uniserial, non-conjugate; plating simple with tubercle on every third plate, this tubercle being not much larger than the granulation; in between there is granulation, sometimes merged to form lateral epistromal bars. From the ambitus adorally plating becomes trigeminate with a large primary tubercle.
  • Adoral ambulacra expanded to form short phyllodes. Plating apparently simple adapically, with all elements reaching the perradius; trigeminate subambitally, but details of plate compounding not discernable (primary tubercle probably overlaps two of the three elements).
  • Interambulacra a little wider than ambulacra. Aboral plates lacking primary tubercle and covered in small, dense granules. At the ambitus plates each with a large primary tubercle; tubercles largest at ambitus, decreasing in size adorally.
  • Primary tubercles with massive imperforate mamelon and no platform.
  • Peristome subcircular, large (about half test diameter), a little sunken. Buccal notches sharp and well defined; presence of tag unknown.
  • Sphaeridial distribution unknown; basicoronal plate presence/structure unknown.
  • Spines unknown.
Distribution Middle Jurassic (Callovian), France.
Name gender masculine
Acrosaster michaleti Lambert, 1910, p. 30, by original designation.
Species Included Only the type species.
Classification and/or Status

Euechinoidea, Echinacea, Arbacioida, Glypticidae.



This species is clearly sexually dimorphic, and the structure of the apical disc suggests that eggs were brooded in the adapical interradial channels. No other Glypticidae has such a distinctive apical disc structure. Aboral epistromal ornamentation is much less pronounced in this genus than in Glypticus and Pleiocyphus

Mortensen, T. 1935. A monograph of the Echinoidea II. Bothriocidaroida, Melonechinoida, Lepidocentroida and Stirodonta. C. A. Reitzel, Copenhagen.

Lambert, J. 1911 [for 1910]. Sur trois genres nouveaux d\'Echinides fossiles. Annales de la Societe Linnee de Lyon 57, 27-32.