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The Echinoid Directory

Stomechinus Desor, 1856, p. 124

[=Glyptechinus de Loriol, 1873, p. 169, type species Glyptechinus rochati de Loriol, 1873; =Sirechinus Quenstedt, 1873, p. 359 (objective); =Spaniocyphus Pomel, 1883, p. 81, type species Echinus fallax Agassiz, in Agassiz & Desor, 1846; =Sporotaxis Pomel, 1883, p. 84, type species Stomechinus longuemari Cotteau, 1867; ?=Cretacechinus Lambert & Thiery, 1911, p. 253, type species Stomechinus camarensis de Loriol, 1887 ]

Diagnostic Features
  • Test moderately large; subconical to low hemispherical.
  • Apical disc small, ca 20% test diameter; dicyclic (rarely hemicyclic, with the posterior oculars exsert). Small secondary tubercles scattered over apical disc plates. Periproct relatively large.
  • Ambulacra trigeminate with pore-pairs in arcs of three; middle elements subequal and generally reaching perradius (upper element occasionally not quite reaching the perradius); plate compounding in diadematid style. In type species primary tubercle to every second (rarely third) compound plate with smaller perradial tubercle alternating. Adorally primary tubercle on every plate and covering all three elements.
  • Pore-pairs forming broad adradial band throughout, very slightly expanded adorally.
  • Interambulacral plates much wider than tall. On aboral plates a single small primary tubercle on each; remainder of plate covered in heterogeneous small secondary tubercles and granules. Subambitally there are secondary flanking tubercles on either side of the primary.
  • Aboral interradial zone rather more sparcely tuberculate but no well defined naked band.
  • Primary tubercles imperforate and non-crenulate.
  • Peristome relatively large, hardly invaginated; buccal notches present but shallow.
  • Spines short and simple, no cortex.
  • Lantern stirodont, teeth keeled.
Distribution
Middle Jurassic (Aalenian) to Lower Cretaceous (Aptian) Europe, North America, North Africa.
Name gender masculine
Type
Echinus bigranularis Lamarck, 1816, by subsequent designation of Lambert, 1901, p. 237.
Species Included
  • Lambert & Thiery list many species.
  • S. bigranularis (Lamarck, 1816); Aalenian, Bajocian, western Europe.
  • S. morierei Cotteau, 1880; Bathonian, France.
  • S. tenuis (Desor, 1856); Valanginian, France.
  • S. fallax (Agassiz, 1840); Hauterivian, France.
  • S. hiselyi (Desor, 1856); Hauterivian, France, Switzerland.
Classification and/or Status
Euechinoidea, Echinacea, Stomechinidae.
Remarks

Very close to Echinotiara in appearance and tuberculation style, differing primarily in having offset pore-pairs forming a broad band from the apex. In Echinotiara the pore-pairs form a single irregular series above the ambitus.

Distinguished from Psephechinus and Polycyphus in having a primary tubercle on every other plate.  Alternate plates have either just secondary tubercles and granules, or have an enlarged secondary tubercle forming an inner series.

Desor, E. 1855-1858. Synopsis des échinides fossiles. Reinwald , Paris, lxviii+490 pp., 44 pls.