The Echinoid Directory

Epiaster d'Orbigny, 1853, p. 186

[=Tainiaster Lambert, 1895, p. 158 (non Taeniaster Billings, 1858) ]

Diagnostic Features
  • Test cordiform with shallow anterior sulcus; posterior face obliquely truncate; lower surface flat. Ambitus rounded.
  • Apical disc ethmophract with four gonopores; positioned centrally.
  • Anterior ambulacrum weakly depressed from apex to peristome; pore-pairs differentiated from those in other ambulacra.
  • Paired ambulacra petaloid and weakly flexed; flush. Petals with pores of each pair elongate and slit-like; open distally; the two columns similar.
  • Peristome small and D-shaped; facing downwards.
  • Oral plating not recorded.
  • Periproct small and rounded; positioned on short posterior truncate face.
  • No fascioles.
  • Aboral tuberculation of small uniform tubercles set in a groundmass of fine granules.
Distribution
Lower to Upper Cretaceous (Barremian - Cenomanian), Europe, North Africa, North America.
Name gender masculine
Type
Spatangus acutus Deshayes, 1831, p. 255 [=Spatangus crassissimus Defrance, 1827, p. 96], by subsequent designation of Lambert, 1895, p. 156.
 
Species Included
  • E. crassissimus (Defrance, 1827); Upper Albian - Cenomanian, western Europe.
  • E. distinctus (Agassiz in Agassiz & Desor 1847); Upper Albian - Cenomanian, western Europe.
  • Many others have been assigned but need to be checked.
Classification and/or Status

Spatangoida, stem group (toxasterids).

Probably paraphyletic by exclusion of the micrasterids.

Remarks

The genus, as conceived by d'Orbigny, 1853, contained a polyphyletic mixture of species, and there has been some confusion concerning which is the type species. In the section of the Paleontologie francaise in which d'Orbigny initially set up the genus Epiaster he listed and described just three genera, E. polygonus, E. trigonalis, and E. tumidus. In a subsequent section, published slightly later, he described some further species, including E. crassissimus. Lambert, in 1895,  selected E. crassissimus as type species of Epiaster, but later (in Lambert & Thiery 1921, p. 447) replaced this with E. trigonalis.

Pomel, 1883, p. 43, stated “Types E. trigonalis d’Orb., E. tumidus d’Orb., E. acutus Des.”; this was not a valid type designation, nor was it valid for Mortensen (1950, p. 345) to deduce from Pomel’s statement “that the first of these, trigonalis, must be the genotype”. Lambert & Thiery, 1924, p. 477 had previously stated erroneously that trigonalis was the type species.

Smith (1988, p. 173)  pointed out that in the published part in which Epiaster was established d’Orbigny described only polygonus, trigonalis and tumidus, while further species, including crassissimus, were described in the next published part. Smith concluded from this that crassissimus was not amongst the species placed by d’Orbigny in Epiaster at the time of publication.  Indeed, d’Orbigny stated on p. 187 that he established Epiaster for the species polygonus, trigonalis, acutus, distinctus and aquitanicus included in Micraster by Agassiz.  Subsequently (on p. 194) he records acutus as a junior synonym of crassissimus, and so in fact crassissimus is available for selection as type species by Savin.

Epiaster differs from Toxaster in having a genital plate 2 separating the posterior genital plates in the apical disc, and by possessing pore-pairs in the anterior ambulacrum that are differentiated from those in the paired ambulacra. It differs from Pliotoxaster in having the paired ambulacra flush, not sunken.

d'Orbigny, A. 1854-60. Paléontologie Française. Terrains Crétacés. Tome 6. Echinodermes, Échinoides irréguliers. 596 pp, pls 801-1006. G. Masson, Paris. 1-32 (July 1854); 33-64 (Oct. 1854); 65-96 (Nov. 1854); 97-128 (Jan. 1855); 129-192 (Mar. 1855); 193-208 (May 1855); 209-224 (Aug. 1855); 225-272 (Nov. 1855); 273-320 (Oct. 1856) pp. 273-352 (Oct. 1856), pp. 353-384 (1857), pp. 385-400 (1858), pp. 401-432 (1858), pp. 433-596 (1860).

Smith, A. B. 1988. Echinoidea. In: SMITH, A. B., PAUL, C. R. C., GALE, A. S. & DONOVAN, S. K., Cenomanian and Lower Turonian echinoderms from Wilmington, S. E. Devon. Bulletin of the British Museum (Natural History) (Geology), 42 (1), 16-188.

Smith, A. B.. & Wright, C. W. 2008. British Cretaceous echinoids. Part 8, Atelostomata, 2. Spatangoida (1). Monograph of the Palaeontographical Society London, 162 (630), 569-635, pls 183-209.