The Echinoid Directory

Contributed by Andrew Smith, January 2017

Cunidentechinus Smith, 2016, p. 69

Diagnostic Features
  • Small, regular echinoid with a large apical disc whose plates are not firmly bound to the corona. Plating unknown but presumed monocyclic.
  • Ambulacra narrow, straight; ambulacral plating simple and uniform, with every third element bearing a primary tubercle; Pore-pairs small and uniserially aligned.
  • Interambulacral plates bear a single large primary tubercle with a small, perforated mamelon and strongly crenulated platform.
  • Peristome and apical disc similar in area.
  • Teeth trapezoidal in cross-section, incorporating large triangular secondary plates. Pyramids with deep foramen magnum.
  • Spines simple, needle-like and much longer than the diameter of the test.
Distribution Lower Jurassic (Sinemurian- Pliensbachian) of western Europe.
Type Echinus minutus Buckman, in Murchison, 1845, by original designation.
Species Included Only the type species.
Classification and/or Status Stem group Carinacea
Remarks The test of Cunidentechinus resembles that of Aspidodiadematoida in many ways. Apical disc plates are never preserved within the large apical disc opening and were presumably membrane-embedded as in aspidodiadematids, rather than firmly abutting the corona. The simple ambulacral plating, with every third element bearing a small primary tubercle, is also very like that of the aspidodiadematoid Plesiodiadema. However, aspidodiadematoids all have grooved teeth whereas Cunidentechinus has wedge-shaped teeth like those of irregular echinoids and some miniaturized saleniids. The taxon is therefore an early member of the Carinacea, the most primitive yet found, and a potential stem group member to both Irregularia and living regular Carinacea.

The lantern of the type species (under the name Eodiadema) was described by Smith (1981).

Smith, A. B. 1981. Implications of lantern morphology for the phylogeny of post-Palaeozoic echinoids. Palaeontology 24, 779-801.

Smith, A. B. 2016. British Cretaceous regular echinoids. Part 2 Carinacea. Monographs of the Palaeontographical Society (no. 646), pp. 69-176, pls 42-82.