The Echinoid Directory

Prototiara Lambert, 1900, p. 34

Diagnostic Features
  • Test small, flattened above and below.
  • Apical disc relatively large; subpentagonal; plating lost.
  • Ambulacra straight, narrow; composed entirely of simple elements aborally and adorally, but with small primary tubercles overlapping two elements in every three subambitally; all elements reach perradius. Pore-pairs strongly oblique and uniserially arranged throughout.
  • Perradial portion of ambulacral plate of same width as the pore zone; each plate with one or two granules or secondaries only. One or two enlarged primary tubercles in each zone in subambital region, but always much smaller that adjacent interambulacral tubercles.
  • Interambulacral plates relatively tall, each with a rather large primary tubercle; tubercles non-crenulate and with a rather large imperforate mamelon. Areoles circular, weakly incised and separated by granules in each column. The remainder of the plate with rather dense and somewhat heterogeneous granules and epistroma.
  • Peristome a little over 50% test diameter and flush; buccal notches very weakly defined but present.
  • Spines and lantern unknown.
Distribution Jurassic (Pliensbachian-Bathonian); Europe.
Name gender feminine
Type Pleruodiadema jutieri Cotteau, 1883, p. 548, by original designation.
Species Included
  • P. jutieri (Cotteau, 1883); Upper Pliensbachian, France.
  • P. loryi Lambert, 1910; Bathonian, France.
  • P. mestreae Lambert, 1922; Bajocian, Spain.
Classification and/or Status Euechinoidea, Carinacea, ?Echinacea incertae sedis

Subjective junior synonym of Leptechinus Gauthier, 1889
Remarks The simple ambulacra with their cluster of epistroma, and the large imperforate mamelons without crenulation suggest possible arabacioid affinities.  However, the clusters of similar-sized granules and predominantly simple ambulacral plating makes this very distinct.

Lambert, J. 1900. Étude sur quelques Échinides de l'Infra-Lias et du Lias. Bulletin de la Société des Sciences Historiques et Naturelles de l'Yonne 52 (1899)(2): 3-57.