The Echinoid Directory

Catopygus L. Agassiz, 1836, p. 185

Diagnostic Features
  • Test small, oval, highly inflated adapically, pointed posterior margin; flat, or slightly convex adorally.
  • Apical system tetrabasal, anterior, with four genital pores; genital plate 2 much larger than other genital plates.
  • Petals equal, flush with test, open distally. Pores conjugate, with outer pore slightly elongate. All ambulacral plates double pored.
  • Periproct marginal, towards top of vertically truncate posterior face; longitudinal, not visible from above.
  • Peristome anterior, pentagonal, higher than wide; opening sunken with vertical-walled vestibule.
  • Bourrelets moderately developed as small mounds.
  • Phyllodes broad, double pored, with pore-pairs in two series in each half-ambulacrum, inner or lower pore of a pore-pair usually smaller. Inner pore-pairs on demiplates.
  • No buccal pores.
?Kimmeridgian (Late Jurassic) to Maastrichtian (Late Cretaceous), worldwide distribution.
Name gender masculine
Nucleolites carinatus Goldfuss, 1826, p. 142 [=Nucleolites columbaria Lamarck, 1816, p. 37]; by subsequent designation of Cotteau, 1869, p. 121.
Species Included
  • C. columbarius (Lamarck, 1816); Upper Aptian to Cenomanian, Europe. [includes C. vectensis Wright, 1875]
  • C. fenestratus Agassiz, in Agassiz & Desor, 1847; Maastrichtian, western Europe.
  • C. conoideus Tzankov, 1934; Maastrichtian of North Bulgaria.

Lambert & Thiery (1909-1925) list some 25 species within this genus.

Classification and/or Status
Irregularia; Neognathostomata; 'catopygids'.

Catopygus is very similar to Phyllobrissus. The type species of both genera are very similar in appearance, both having the same petal arrangement, and phyllodes with two series of pore-pairs in each half-ambulacrum; the inner pore of each pair greatly reduced in size. For this reason Lambert (1902, p. 15) and Mortensen (1948, p. 167) suggested that Phyllobrissus might be considered a subgenus of Catopygus. Kier (1962, p. 76) points out that Phyllobrissus gresslyi is slightly broader, with a more depressed adapical surface, and an obliquely truncated posterior margin, exposing the periproct adapically. In Catopygus carinatus the posterior margin is pointed, and the periproct not visible from above. However, Kier (1962, p. 76) adds that although these differences may be sufficient to distinguish these genera, there are some species that have some of the characters of both type species, making it very difficult to decide to which of the two genera to assign them.

Catopygus closely resembles Pygaulus in test shape, petal arrangement, and position and shape of the periproct. Catopygus differs in having a pentagonal peristome, wide phyllodes and well-developed bourrelets.

Catopygus is differentiated from Penesticta by its broader, more developed petals, in which the pore-pairs are closer to each other than in Penesticta (Smith & Wright (2000, p. 419) and by having four gonopores (gonopore present in genital plate 2), while Penesticta has only three (no gonopore in genital plate 2).

Agassiz, L.1836. Prodrome d'une monographie des Radiaires ou Échinodermes. Mémoires de la Société des Sciences naturelles de Neuchâtel, 1, 168-199.

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

J. Lambert & P. Thiery. 1909-1925. Essai de nomenclature raisonnee des echinides. Libraire Septime Ferriere, Chaumont, 607 pp., 15 pls.

T. Mortensen. 1948. A monograph of the Echinoidea: 4 (1): Holectypoida, Cassiduloida. Reitzel, Copenhagen, 363 pp., 14 pls.

A. B. Smith & C. W. Wright. 2000. British Cretaceous echinoids. Monograph of the Palaeontographical Society, pp. 391-439, pls 130-138.