The Echinoid Directory

• Test wheel-shaped, flattened below and above.
• Apical disc small, subcircular; plating not firmly bound to corona; always lost.
• Ambulacra polygeminate, approximately 5-6 elements to a compound plate. Plate compound style unclear, but basically phymosomatid. pore-pairs biserial to ambitus , very briefly arcuate then expanded adorally into well developed phyllodes.
• Ambulacral plates with single large tubercle; secondaries forming zig-zag line up perradius.
• Interambulacral plates wider than tall. A single primary tubercle centrally placed , with much smaller secondary flanking tubercles on adradial and interradial sides on ambital and adoral plates, these approaching size of primaries on subambital plates. Secondary tuberculation generally rather coarse.
• Ambulacral and interambulacral tubercles of similar size.
• No well defined aboral naked interradial zone.
• Primary tubercles imperforate and non-crenulate; mamelon rather massive.
• Peristome large, almost flush; buccal notches deep and sharp.
• Spines and lantern unknown; no primordial interambulacral plate.

Cretaceous, Germany

Leiosoma tournoueri Cotteau, 1867, p. 768, by original designation

• P. tournoueri (Cotteau, 1866); 'Senonian' (Maastrichtian or Palaeocene), France.
• P. selimi Peron & Gautheir, 1881; Campanian, Algeria.
• Maybe also P. jauberti (Cotteau, 1863); Bathonian, France - with weak crenulation but same style of plate compounding

Euechinoidea, Echinacea, Stomopneustoida, Stomopneustidae

 

Cotteau, G. 1862-67. Paleontologie francaise. Terrain Cretace VII. Echinides. Mason, Paris.

Lambert, J. & Thiery, P. 1909-1925. Essai de Nomenclature Raisonnée des Echinides. L. Ferrière, Chaumont, fasc. 1: i-iii, 1-80, pls 1-2 (March 1909); fasc. 2: 81-160, pls 3-4 (July 1910); fasc. 3: 161-240, pls 5-6 (May 1911); fasc. 4: 241-320, pls 7-8 (March 1914); fasc. 5: 321-384, pl. 9 (Sept. 1921); fasc. 6-7: 385-512, pls 10-11, 14 (Dec. 1924); fasc. 7-8: 513-607, pls 12, 13, 15 (Feb. 1925).