The Echinoid Directory

Nortonechinus Thomas, 1924, p. 481

[?=Xenocidaris Schultze, 1866, p. 126, type species Xenocidaris clavigera Schultze, 1866 ]

Diagnostic Features
  • Test shape unknown; plating thin and imbricate.
  • Apical disc unknown.
  • Ambulacra more or less straight and narrow; biserial throughout. Plating simple and uniform with pore-pair on each plate, positioned adradially. Small tubercles perradially.
  • Internally ambulacral plates with perradial flange that fully enclose the radial water vessel.
  • Interambulacral zones wide; composed of up to 19 regular columns of polygonal plates. Each plate with large tongue-like imbrication flange.
  • All interambulacral plates with a large perforate primary tubercle; areolar zone weakly sunken; surrounded by widely spaced ring of scrobicular tubercles.
  • Peristome unknown.
  • Lantern with broad pyramid with modest foramen magnum; rotulae rather narrow and hinge-jointed; teeth unknown.
  • Spines short and nail-like with expanded, polygonal end. These spines form a continuous pavement over the test.
Distribution
Upper Devonian, USA, ?Middle Devonian, Germany.
Name gender masculine
Type
Nortonechinus welleri Thomas, 1924, p. 481, by original designation.
Species Included
  • Nortonechinus welleri Thomas, 1920; Upper Devonian, Iowa, USA.
  • N. sp. Kier 1968; Upper Devonian, Iowa, USA.
  • ?N. clavigera (Schultze, 1866); Middle Devonian, Germany.
Classification and/or Status

Stem group Echinoidea; Archaeocidaridae.

Presumed monophyletic.

Remarks

The test is very similar in form to Lepidocidaris, but the spines immediately distinguish this taxon from all others. Lepidocidaris also has more heterogeneous ambulacral plating, whereas the plating in Nortonechinus is rather uniform and the pore-pairs are uniserially aligned. Xenocidaris was based on isolated spines that are broadly similar to those of Nortonechinus, but which are a little more slender and with a domed and spiked distal terminus. In the absence of associated interambulacral plates they are tentatively synonymized.

Thomas, A. O. 1924. Echinoderms of the Iowa Devonian. Iowa Geological Survey Annual Report 29, 385–552.

Kier, P. M. 1968. Nortonechinus and the ancestry of the cidaroid echinoids. Journal of Paleontology 42, 1163-1170, pls 151-153.