The Echinoid Directory

• Test wheel-shaped, flattened below and above.
• Apical disc large, pentagonal, about half of the test diameter; plating not firmly bound to corona; always lost.
• Ambulacra trigeminate throughout, Plate compounding diadematid-style with middle element the largest and all three elements reaching the perradial suture.
• Pore-pairs arranged biserially above the ambitus and uniserial and arcuate at ambitus; becoming offset and crowded close to the peristome.
• Ambulacral plates with single large tubercle leaving little perradial space
• Interambulacral plates much wider than tall, slightly flexed; plates at the ambitus much lower than those either adapically or adorally. Plates with a single row of subequal tubercles, up to 8 abreast; little space for granules.
• Ambulacral and interambulacral tubercles of similar size. Tubercles imperforate and non-crenulate; mamelon relatively large and little or no surrounding platform.
• Narrow naked interradial zone.
• Peristome large, very slightly sunken; buccal notches small but sharp.
• Spines and lantern unknown; no primordial interambulacral plate.

Upper Cretaceous (Campanian-Maastrichtian), Caribbean, North Africa, Arabian Peninsula, Middle East.

Plistophyma africanum Peron & Gauthier, 1881, p. 177, by monotypy.

• P. cubense (Egozcue, 1897); Campanian-Maastrichtian, Cuba.
• P. africanum Peron & Gauthier, 1881; Maastrichtian, Algeria.
• P. asiaticum Cotteau & Gauthier, 1895; Maastrichtian, Arabian Peninsula, Iran.

Calycina, Phymosomatoida, unnamed family

Plistophyma is close to Gomphechinus differing in having polygeminate ambulacral plating and no shortening of ambital plates at the ambitus. Winkleria is identical in tuberculation pattern and in having short ambital interambulacral plates, but has simple plating adapically and bigeminate plating adorally.

Cotteau, G., Peron, A. & Gauthier, V. 1873-1881. Echinides fossiles de l'Algerie, fascicules I-X. Masson, Paris.

Smith, A. B. 1995. Late Campanian-Maastrichtian echinoids from the United Arab Emirates - Oman border region. Bulletin of the Natural History Museum, London (Geology) 51, 121-240, pls 1-34.

Smith, A. B. & Jeffery, C. H. 2000. Maastrichtian and Palaeocene Echinoids: a key to world faunas. Special Papers in Palaeontology 63, 1-404