The Echinoid Directory

Rhyncholampas A. Agassiz, 1869, p. 270

[=Anisopetalus Clark in Arnold & Clark, 1927, p. 44, type species Anisopetalus ellipticus Clark in Arnold & Clark, 1927, p. 44; =Plagiopygus Lambert, 1898, p. 162, type species Nucleolites grigonensis de France, 1825; =Pleuropygus Lambert & Thiery in Lambert, 1913, p. 127, type species Nucleolites grigonensis de France, 1825; =Galerolampas Cotteau, 1889, p. 1, type species Galerolampas sorigneti Cotteau, 1889; =Gisopygus Gauthier, in Fourtau, 1899, p. 648, type species Rhynchopygus navillei de Loriol, 1881]

Diagnostic Features
  • Test subovate with greatest width posterior of centre, moderately inflated aborally.
  • Apical system anterior; monobasal with four gonopores.
  • Petals lanceolate, converging distally but not closed. Columns of pore pairs in each petal of unequal length; interporal zone much wider than pore zones.
  • Ambulacra single pored beyond petals.
  • Periproct just supramarginal or marginal; transverse. Slight subanal depression.
  • Peristome anterior, pentagonal, wider than high.
  • Bourrelets forming weakly projecting nodes; largely confined to vertical walled entrance to the peristome.
  • Phyllodes single pored; widened; with two series of pores in each half-ambulacrum, inner series rather irregular; in some species three series of pores in each half-ambulacrum.
  • Buccal pores present.
  • Tubercles on adoral surface much larger than on adapical; scrobicules large, bosses eccentric towards anterior.
  • Naked, smooth, in places pitted area interambulacrum 5, and ambulacrum III on oral surface.
Upper Cretaceous (Maastrichtian) to Recent; worldwide distribution.
Name gender feminine
Pygorhynchus pacificus A. Agassiz, 1863, p. 27, by subsequent designation of Lambert, 1918.
Species Included
  • R. pacificus A. Agassiz 1863; Recent, Tropical Eastern Pacific Ocean.
  • R. conradi (Conrad, 1850); Tertiary (Late Eocene), USA.
  • R. pygmaeus (Duncan & Sladen, 1882); Late Thanetian, Pakistan.
  • R. macari (Smiser, 1935); Maastrichtian, Maastricht, The Netherlands, Belgium, Spain, Uzbekistan.
  • R. ellipticus (Clark in Arnold & Clark, 1927); Eocene, Jamaica.
  • R. navillei (de Loriol, 1881); Lower Eocene, Egypt.
  • R. smithi Srivastava et al. 2008; Eocene (Lutetian-Bartonian), India.
  • R. sorigneti (Cotteau, 1889); Middle Eocene, France.
Classification and/or Status
Irregularia; Cassiduloida; Cassidulidae.

Rhyncholampas is distinguished from Cassidulus by its larger test, broader, lanceolate petals, generally more posterior periproct, and more developed phyllodes with more occluded plates. However, these differences are largely size related and it is not clear that there is sufficient evidence to merit keeping the two genera separate. Echinolampas is very similar but its periproct is inframarginal.

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