The Echinoid Directory

• Test relatively tall and thin-plated.
• Apical disc about 40% of test diameter; similar in size to peristome; ocular plates just exsert except for ocular plate III which is insert.
• Interambulacra with approximately 7 plates in a series. Plates almost as tall as wide at ambitus and with primary tubercles widely separated. Primary tubercles perforate, non-crenulate except for adapical tubercles which have crenulation developed around the adapical side of the platform; mamelons moderate in size. Areoles circular and incised; widely separated even subambitally.
• Scrobicular tubercles small and weakly differentiated; forming a distinct rim around the areoles. Extrascrobicular tuberculation sparse and scattered, leaving the margins of ambital and adapical plates almost nude.
• No sutural pits or furrows; sutures not depressed.
• Ambulacral zones more or less straight. Pore zones not incised. Pore-pairs conjugate with pores linked by a groove. Perradial zone with marginal series of contiguous primary tubercles and only the occasional much smaller tubercle perradially leaving the perradius very sparsely tuberculate.
• Ambulacral tubercles uniform throughout.
• No test known with attached spines.

Middle Jurassic (Bathonian-Callovian), France.

Rhabdocidaris bigoti Mercier, 1930, p. 94, by original designation.

• Only the type species.

Cidaroida, ?Polycidaridae.

Monotypic; subjective junior synonym of Nudicidaris Vadet, 1991.

The taxon was erected by Vadet (1991) but without clear differential diagnosis. In Vadet et al. (1996) it is distinguished from Rhabdocidaris in having only the adapical two primary tubercles crenulate, ambital and adoral tubercles being apparently non-crenulate. It is very close in appearance to Nudicidaris, differing only in having subconjugate pore-pairs. Vadet (2004) erected another genus Remycidaris which he separated from Nudicidaris on the basis of its slightly wider pore-pairs. It is likely that both Remycidaris and Guittonicidaris are based on the same type species. All three genera are treated here as synonyms.

Vadet, A. 1991. Revision des "Cidaris" du Lias et du Dogger Europeens. Memoires de la Societe academique du Boulonnais 10, 1-176.

Vadet, A, Nicolleau, P. & Pineau, J. P. 1996. Echinides du Callovien de la Sarthe et de l'Orne. I: Les echinides reguliers. Memoires de la Societe academique du Boulonnais 17, 1-184.

Vadet, A. 2004. Echinides fossiles du Boulonnais. Du Bajocien au Tithonien: les "Cidaris". Annales de la Societe d'Histoire Naturelle du Boulonnais 3, 1-35.