The Echinoid Directory

• Test wheel-shaped, depressed above and below.
• Apical disc large, pentagonal, up to 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), compounded in phymosomatid style. Pore-pairs undifferentiated; arranged as weak arcs across entire oral surface and most of aboral surface except adapically, where they become biserially arranged. No phyllodes.
• A single primary tubercle to each compound plate; additional small secondaries and granules forming zig-zag line down perradius.
• Interambulacral plates wider than tall; with a single large primary tubercle, positioned centrally, and scattered secondaries and granules interradially at the ambitus. There is a well developed naked interradial zone present aborally, expanding towards the apex. Small secondary tubercle flank the primary on adoral plates.
• Tubercles with massive mamelon; imperforate and crenulate.
• Peristome small, circular, rather deeply sunken, with small, but clearly defined buccal notches with thickened lip; no tag.
• No sphaeridial pits; no basicoronal interambulacral plate.
• Spines and lantern unknown.

Upper Cretaceous (Campanian-Maastrichtian) to Palaeocene, Europe and central Asia.

Cidarites (Diadema) princeps von Hagenow, 1840, p. 651, by original designation.

• G. princeps (Hagenow, 1840); Campanian-Maastrichtrian, Europe
• G. krimica (Weber, 1934); Maastrichtian of Belgium and Denmark; Danian of Poland, Ukraine and the Crimea, Turkmenia and Kazakhstan.

Euechinoidea, Phymosomatoida, Phymosomatidae.

Subjective junior synonym of Cosmocyphus Pomel, 1883

Distinguished from Phymosoma by (i) very small development of biserial pore-pairs (ii) deeply sunken peristome (iii) no phyllodes. Close to Gauthieria, but in that genus the pore-pairs remain strictly uniserial to the apex. However, Gauthieria species are generally a little smaller and this may simply be a size-related feature.

Kutscher, M. 1985. Neue Echiniden aus dem Unter-Maastricht der Insel Rugen. Zeitschrift fur geologische Wissenschaften 13: 521-532.

Smith, A. B. & Wright, C. W. 1996. British Cretaceous Echinoids. Part 4, Stirodonta 3 (Phymosomatidae, Pseudodiadematidae) and Camarodonta. Monograph of the Palaeontographical Society (publication no. 602, part of vol. 150), 268-341, pls 93-114.