The Echinoid Directory

Contributed by Andrew Smith, September 2006

Monodiadema de Loriol, 1890, p. 58

[=Recrosalenia Currie, 1925, p. 47, type species Recrosalenia somaliensis Currie, 1925 ]

Diagnostic Features
  • Test subpentagonal; a little inflated in profile, with rounded ambitus.
  • Apical large, projecting distinctly towards posterior; plating caducous; length about 50% test diameter.
  • Ambulacra straight; pore-pairs uniserial. All elements reaching the perradius and of similar size, but arranged in triads at ambitus and below (two of every three elements overlapped by a larger tubercle and alternating with a simple element with a tubercle only slightly smaller).
  • On ambital ambulacral plates there are two columns of tubercles per plate - a slightly larger adradial row alternating with a row of slightly smaller perradial tubercles. Close to peristome a large tubercle straddles all three elements.
  • Interambulacral plates wider than tall. Each plate with a large primary tubercle that is perforate and crenulate; the mamelon relatively small. Areoles ovate and confluent at ambitus and adorally. Interradial zone of secondary tubercles well developed at ambitus and aborally; a single line of adradial secondary tubercles also present.
  • Peristome hardly sunken, less than 50% test diameter.
  • Buccal notches sharp and well defined.
  • Spines and lantern unknown.
Distribution Middle to Upper Jurassic (Bathonian-Kimmeridgian), Portugal, North Africa.
Name gender neuter
Type Monodiadema cotteaui de Loriol, 1890, p. 58, by original designation. Types: Geological Survey of Portugal. ?Syntypes: de Loriol Collection, Museum d\'Histore Naturelle, Geneva 25247.
Species Included
  • M. cotteaui de Loriol, 1890; Oxfordian, Portugal, Tunisia.
  • M. libyca (Peron & Gauthier, 1883); Kimmeridgian, Algeria.
  • M. somaliensis (Currie 1925); Bathonian-Callovian, Somalia.
Classification and/or Status Euechinoidea, Acroechinoidea, Diadematoida, Heterodiadematidae
Remarks Distinguished from Emiratiidae by having ambulacral tubercles very much smaller than interambulacral tubercles even at the ambitus. Distinguished from acrosaleniids by its distinctive ambulacral tuberculation (without large primary tubercles) and by its caducous apical disc. Its ambulacral tubercles are reminiscent of the pattern seen in the diadematoid Echinothrix. Lantern structure of Monodiadema is needed to confirm its taxonomic placement within the Diadematoida.

de Loriol, P. 1890. Description de la faune jurassique du Portugal. Embranchement des échinodermes, 1. Échinides réguliers ou endocycles. Mémoires de la Commission des Travaux géologiques du Portugal, 109 pp., 18 pls.