The Echinoid Directory

Pseudonucleus Lambert, 1920, p. 17

Diagnostic Features
  • Test small, ovate in outline, slightly truncate at rear, apical surface highly inflated, and a little depressed in profile with a flat base.
  • Apical disc slightly anterior of centre; no plating discernible; no gonopores open in holotype (Kier, 1962, p. 97 reports that it is tetrabasal with four gonopores).
  • Anterior ambulacrum flush, with strong vertical component. Pore-pairs non-petaloid; small oblique and in pits.
  • Paired petals with small double pores; weakly developed; about five pore-pairs in a column in the anterior petals and eight in the posterior.
  • Peristome pentagonal, not sunken, slightly wider than long.
  • Periproct transverse with slight projecting roof; on posterior face.
  • Bourrelets hardly developed forming vertical-sided entrance to peristome.
  • Phyllodes weakly developed; single irregular column of single pores.
  • Buccal pores present.
  • Posterior interambulacrum on oral surface with distinct perradial zone of pits free of tubercles.
Campanian, Upper Cretaceous of Spain.
Name gender masculine
Pseudonucleus malladai Lambert, 1919, p. 18; by monotypy. Holotype: Museum National d\'Histoire Naturelle, Paris J01640.
Species Included
  • Only the type species.
Classification and/or Status

Irregularia; Cassiduloida; Indeterminate.



Although Kier (1962) treated this as a possible synonym of Oologpygus this seems unlikely because of the differentiation of pores in the frontal ambulacrum and the posterior pitted zone on the oral surface. It is most probably related to Pseudopygaulus, which differs in having an inframarginal periproct.

Lambert, J. 1918. Considérations sur la classification des Échinides Atélostomes. I. Brachygnata et Procassiduloida . Mémoires de la Société Académique d'Agriculture des Sciences, Arts et Belles-Lettres du Département de l'Aube, Troisième Série 55 (Vol. 82 of the whole series), 9-54.

J. Lambert. 1919. Echinides des environs de Santander recueillis par M.L. Mengaud. Annales de la Societe Linneenne de Lyon 1919.

P. M. Kier. 1962. Revision of the cassiduloid echinoids. Smithsonian Miscellaneous Collections, 144 (3) 262 pp.