The Echinoid Directory

Lychnidius Pomel, 1883, p. 55

Diagnostic Features
  • Test very small, oval, inflated, with rounded margin.
  • Apical system anterior; tetrabasal with four gonopores.
  • Petals poorly developed, short, tending to taper distally, but remaining open; posterior pair longest, but not reaching level of anal sulcus; interporiferous zones approximately the same width as poriferous zones; pores subconjugate, both inner and outer of pair round; ambulacral plates single pored beyond petals.
  • Periproct supramarginal, longitudinal, high on oblique posterior face and supraambital; feeble sulcus.
  • Peristome central, depressed, subpentagonal, with vertically walled entrance.
  • Bourrelets confined to vertical-walled entrance to the peristome.
  • Phyllodes single pored, no widening of area adorally, slight crowding.
  • Tubercles approximately the same size adapically and adorally.
  • Slight naked, granular zone in interambulacrum on some specimens, absent on others.
Upper Cretaceous (Maastrichtian) of Holland and Belgium.
Name gender masculine
Nucleolites scrobiculatus Goldfuss, 1826, p. 138, by monotypy.
Species Included
  • Only the type species.
Classification and/or Status

Irregularia; Cassiduloida; Apatopygidae.

Subjective junior synonym of Nucleopygus L. Agassiz, 1840.


Lychnidius is very similar to Nucleopygus, with the tests of both genera being small, elongate, with supramarginal, longitudinal periproct, petals poorly developed, pentagonal transverse peristome, moderately developed bourrelets, slightly crowded single-pored phyllodes and tetrabasal apical system.

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

J. W. M. Jagt. 2000. Late Cretaceous-Early Paleogene echinoderms and the K/T boundary in the southeast Netherlands and northeast Belgium - Part 4: Echinoids. Scripta Geologica 121, 352-353.

Pomel, A. 1883. Classification méthodique et Genera des Échinides vivante et fossiles. Thèses présentées a la Faculté des Sciences de Paris pour obtenir le Grade de Docteur ès Sciences Naturelles 503, Aldolphe Jourdan, Alger, 131 pp.