The Echinoid Directory

• Test depressed with rounded ambitus; weakly domed above.
• Apical disc large, pentagonal, a little less than half test diameter in length, extending slightly into posterior interambulacrum. Plates not bound to corona, always missing; presumed monocyclic.
• Ambulacra straight; plating polygeminate (5-6 elements to a plate adorally, up to 15 elements to a plate adapically), compounded in phymosomatid style. Pore-pairs undifferentiated; biserially arranged aborally to the ambitus, in arcs subambitally and uniserial adorally (no phyllodes).
• A single primary tubercle to each compound plate. Very small secondaries and granules forming zig-zag line down perradius.
• Interambulacral plates wider than tall; with a single primary tubercle, positioned centrally, with sunken areole. At ambitus very much smaller secondary tubercles, usually two to a plate, flanking. A well developed naked interradial zone present aborally.
• Tubercles imperforate and crenulate. On adoral surface areoles typically show a radial ornament.
• Peristome small, circular, sunken, with small, but clearly defined buccal notches with thickened lip; no tag.
• No sphaeridial pits; no basicoronal interambulacral plate.
• Spines unknown.
• Lantern unknown.

Upper Cretaceous (Campanian-Maastrichtian); Iran and the Middle East.

Actinophyma spectabile Cotteau & Gauthier, 1895, p. 96, by original designation.

• Only the type species.

Euechinoidea, Phymosomatoida, Phymosomatidae.

Distinguished from Phymosoma by the very much greater number of elements forming aboral ambulacral plates (10-12 as opposed to 5-6), and by the sunken peristome and lack of phyllodes. Distinguished from Acanthechinus by having primary tubercles with decidedly incised areoles, often with radial ornamentation on those of the oral surface. It also has a proportionally larger apical disc.

Cotteau, G. & Gauthier, V. 1895. Mission scientifique en Perse par J. Morgan. 3. Etudes geologiques, partie 2. Paleontologie: premiere partie. Echinides fossiles. E. Leroux, Paris, 142 pp., 16 pls.

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.