The Echinoid Directory

Atlasaster Lambert, 1931, p. 19

Diagnostic Features
  • Test moderately large; subconical with flat base.
  • Apical disc ca 20% test diameter; ovate and projecting slightly into the posterior interambulacrum. Plating hemicyclic; anterior genital plates pentagonal and large; genital plate 5 more slender and U-shaped, with a gonopore in A. jeanneti but not in A. termieri. Ocular plates I and V exsert, the anterior ocular plates insert. Periproct ovate, with smooth rounded border to the posterior but probably with angular periproctal plates around anterior.
  • Ambulacra trigeminate with pore-pairs in arcs of three; all elements subequal and reaching perradius; plate compounding in acrosaleniid style with marginal primary tubercle covering two of every three element.
  • Pore-pairs small and undifferentiated; every third pore-pair offset.
  • Interambulacral plates much wider than tall. On aboral surface, plates with single small primary tubercle slightly offset towards adradial suture. Remainder of plate covered in heterogeneous small secondary tubercles and granules.
  • On oral surface numerous larger subequal tubercles arranged linearly along each plate.
  • Primary tubercles perforate and crenulate.
  • Peristome relatively small (ca. 15% test diameter), distinctly invaginated; buccal notches probably present.
  • Spines and lantern unknown.
Lower Jurassic (Sinemurian - Pleinsbachian), Morocco.
Name gender masculine
Atlasaster termieri Lambert, 1931, p. 19.
Species Included
  • A. termieri Lambert, 1931, lower Domerian (early upper Pleinsbachian), Morocco.
  • A. jeanneti Lambert, 1937; Sinemurian, Morocco (may not be congeneric).
Classification and/or Status
Euechinoidea, Stem group Irregularia.

The narrow imperforate genital plate 5 and perforate crenulate tuberculation show this to be close to Pygasterids. It is distinguished from other genera by the unusual arrangement of ambulacral pore-pairs in triads.

Specimens of A. jeanneti Lambert, 1937, show elongate, slit-like outer pores above the ambitus, but this is likely to be the result of surface abrasion. An unabraided specimen (illustrated above) shows the standard uniform pore-pairs.

Lambert, T. 1931. Echinides du Lias du Moyen Atlas marocain. Notes et Memoires du Service des mines et de la Carte geologique Maroc 17, 10-25, 2 pls.

Lambert, J. 1937. Echinides fossiles du Maroc. Notes et Memoires du Service des mines et de la Carte geologique Maroc 39, 39-109. 4 pls.