The Echinoid Directory

Family Micrasteridae Lambert, 1920, p. 158

Diagnosis

 Micrasterine spatangoids with:

  • ethmophract apical disc;
  • aboral tuberculation of small, symmetrical tubercles set in a dense groundmass of granules;
  • subanal fasciole usually present, running along the suture between plates 5.b.2 and 5.b.3;
  • sternal plates paired and symmetric but episternal plates offset; rear of sternal plate abuts ambulacral plate 5;
  • no indentation of posterior interambulacrum behind sternal plates;
  • subanal fasciole crosses the rear of the sternal plates.
Range
Lower Cretaceous (Albian) to Recent; worldwide.
Species Included There are two subfamilies nested within this clade, Ovulasterinae and Cyclasterinae
Classification and/or Status Atelostomata; Micrasterina
Remarks
 Echinoids that possess a subanal fasciole fall into two distinct groups. The Micrasteridae are distinguished from the remainder by their ethmophract apical disc, their alternate episternal plates and the specific pathway followed by the subanal fasciole. They are the more primitive and appear earlier in the fossil record.

The follwoing taxon is too poorly known to include in the key and is only tentatively included in this family:
Sogdiaster Egorov, 1972