The Echinoid Directory

Thomasaster Lambert, 1920, p. 138

[=Tomasia Lambert 1918, p. 32 (non Poche, 1900)]

Diagnostic Features
  • Test of medium size, typically inflated, greatest width posterior to centre, greatest height anterior of centre; with rounded prominence over anterior margin; steep sides, rounded adoral surface, slightly depressed towards peristome
  • Apical system anterior, tetrabasal with four gonopores
  • Paired petals well developed, tapering distally, unequal. petal III absent. Interporiferous zones broad, poriferous zones narrow; pores conjugate. From the above figure, it would appear that ambulacrum III has a single series of double pores, but needs confirming
  • Peristome longitudinal, slightly depressed
  • Periproct inframarginal, longitudinally ovate
  • Bourrelets weak or absent from figure
  • Phyllode structure unknown
  • Buccal pores unknown
Cretaceous (Cenomanian) of Egypt
Name gender masculine
Archiacia araidahensis Gauthier, 1901, p. 46; by subsequent designation of Lambert 1920, p. 154.
Species Included
  • T. araidahensis (Gauthier, 1901); Cenomanian, Egypt
Classification and/or Status

Irregularia; stem group Neognathostomata; Archiaciidae

?Subjective junior synonym of Claviaster d'Orbigny, 1856.


From Gauthier's figures (shown above) Thomasaster would appear to be similar to Claviaster, both genera having a single series of double pores in ambulacrum III. This character differentiates Thomasaster from Gentilia which has a double series of single pores in ambulacrum III.

V. Gauthier 1901, in R. Fourtau. 1902. Notes sur le Echinides fossiles de l'Egypte. Bulletin de l'Institut Egyptien, 4 (2), 23-117 pp., 6 pls.

Lambert, J. 1920. Revue critique Paleozoologie 24, p. 138.

Lambert, J. 1920. Mem. Soc. Acad. Aube 84, p. 154-155.