The Echinoid Directory

Pleurodiadema de Loriol, in Desor & de Loriol, 1871, p. 196

[Phalacrechinus Lambert, 1900, p. 37, type species Pleurodiadema gauthieri Cotteau, 1875 ]

Diagnostic Features
  • Test small, depressed.
  • Apical disc rather large, dicyclic; firmly bound to corona. All plates covered in pustular granules. Periproct small.
  • Ambulacra simple adapically with one granules on each plate; pore-pairs small, oblique and uniserially arranged. Immediately beneath ambitus p-lating becomes trigeminate with large tubercle covering all three elements; tubercles and plating continues like this to peristome. All elements in compound plate reach perradius and upper and lower element slightly smaller than central element.
  • Interambulacral plates only a little wider than tall. Each plate bears a large primary tubercle with a large imperforate mamelon; platform almost obsolete, but in best preserved tubercles there is fine crenulation.
  • Adradial margins of interambulacral zones with lateral grooves and aligned granules close to peristome.
  • Peristome slightly sunken, about 50% test diameter. Buccal notches open and shallow; interambulacral margin raised as a low lip.
  • Spines and lantern unknown.
Distribution Middle to Upper Jurassic (Bathonian - Kimmeridgian), Europe.
Name gender neuter
Pleurodiadema stutzi Desor in Desor & de Loriol, 1871, by original designation. The type species is sometimes attributed to Moesch (1867), but not validly estabilshed in that work (nomen nudum - mentioned without description or illustration).
Species Included
  • P. stutzi Desor in Desor & de Loriol, 1871; Oxfordian, Europe.
  • P. nudum Cotteau, 1875; Kimmeridgian, France.
  • P. gauthieri Cotteau, 1875; Bathonian, France.
Classification and/or Status Euechinoidea, Echinacea, Arbacioida, Glypticidae
Remarks Desor, E. & De Loriol, P. 1868-1872. Échinologie helvétique. Description des oursins fossiles de la Suisse: échinides de la période Jurassique, xi+441 pp., 61 pls. Ch. Reinwald, Paris & C.W. Kreidel, Wiesbaden.

Moesch, C. 1867. Geologische Beschreibung des Aargauer-Jura und der Nördlichen Gebiete des Kantos Zürich. Beitræge zur geologischen Karte der Schweiz, 4, iii-xv, 1-319.