The Echinoid Directory

Xenechinus Kier, 1958, p. 889

Diagnostic Features
  • Test small, subspherical; plating rather thin and tesselate.
  • Apical disc unknown.
  • Ambulacra wide; multiserial, composed of four series of plates, the outer series made of alternately large and small elements. Pore-pairs small and forming 4 discrete, separated columns.
  • Tubercles on ambulacral plates, the largest on the large outer series of plates.
  • The interior of ambulacral plates with short perradial flanges that floor and enclose the radial water vessel.
  • Interambulacra uniserial; much narrower than an ambulacral zone. Plates rectangular, slightly wider than long.
  • Interambulacral plates with one or two central imperforate tubercles, plus smaller marginal granules; primary tubercles similar in size to those on adradial ambulacral plates.
  • No perignathic girdle.
  • Lantern and spines unknown.
Distribution
Lower Permian (Wolfcampian), USA.
Name gender masculine
Type
Xenechinus parvus Kier, 1958, p. 890, by original designation.
Species Included
  • Only the type species.
Classification and/or Status

Stem group Echinoidea; Cravenechinidae.

Monotypic.

Remarks

A small and distinct echinoid close to Cravenechinus. Kier (1958) differentiated this genus from Cravenechinus because of its four rather than 8 columns of ambulacral plates, and because its tubercles are imperforate. However, the tubercles of Cravenechinus may also be imperforate. The two genera are therefore distinguished solely on the number of ambulacral columns developed.

Kier, P. M. 1958. Permian echinoids from West Texas. Journal of Paleontology 32, 889-892, pl. 114.