The Echinoid Directory

Tiarechinopsis Lambert, in Besairie, 1936, p. 120(15)

Diagnostic Features
  • Test small, subconical with flat base sunken towards peristome.
  • Apical disc small (<30% test diameter); dicyclic; plates firmly attached to corona. Plates covered in uniform granulation; gonopores large.
  • Ambulacra straight, trigeminate throughout with pore-pairs arranged in arcs. Compound in diadematid style, with all three elements reaching the perradial suture and with the central element larger than the other two.
  • There is a primary tubercle to each ambulacral compound plate; adapically this occupies mostly the central element, but adorally the tubercles are much larger and fill the complete compound plate. Above the ambitus the perradial zone is relatively wide and small secondary tubercles fill the area; below the ambitus the primary tubercle fills the plate and perradial granulation disappears.
  • Interambulacra wide, composed of 13 plates Plates above the ambitus with small central primary tubercle and rather dense scattering of small, uniform secondary tubercles. Below the ambitus each plate with two large subequal primary tubercles occupying the entire plate height; granules confined to interradial and adradial margins of plate.
  • Primary tubercles (subambital) with massive imperforate mamelon and no platform (non-crenulate).
  • Peristome large; ca. 60% test diameter; sunken; buccal notches not visible.
  • Spines and lantern unknown.
Distribution
Middle Jurassic (Bajocian), Madagascar.
Name gender feminine
Type
Tiarechinopsis besairei Lambert, in Besairie, 1936, p. 120, by original designation. Holotype: Museum National d'Histoire Naturelle, Paris J00570.
Species Included
  • Only the type species.
Classification and/or Status

Euechinoidea, Echinacea, Stomechinidae.

Monotypic.

Remarks

Very close to Stomechinus from which it differs by having a very sharp distinction between apical and adoral tuberculation.

Lambert, J.  1936. Echinides du Senonien superieur et de l'Eocene. In Besairie, H. Recherches geologiques a Madagascar. 1ere suite, La Geologie du Nord-Ouest. Memoires de l'Academie malgache 21, 205-207, 1 pl.