- Test rounded with relatively thin plating; up to 75 mm diameter.
- Apical disc ca. 50% test diameter; dicyclic; genital plates all similar in size; periproctal plating restricted to relatively small central zone; covered in scattered small granules.
- Interambulacra with 6-8 plates in a series. Primary tubercles perforate, crenulate, the mamelons enlarging adapically. Areoles circular, hardly incised and separated.
- Scrobicular tubercles differentiated but small; the circles confluent below the ambitus. Extrascrobicular zones modest; with relatively dense, heterogeneous tuberculation.
- No sutural furrows or pits.
- Ambulacra weakly sinuous; pore zones not sunken; pore pairs conjugate with the two pores widely separated. Perradial zone with a marginal series of contiguous primary tubercles and an inner series of one or two smaller tubercles.
- Adoral ambulacral tubercles heterogeneous with every second tubercle enlarged; ambital and adapical tubercles uniform.
- Peristome subpentagonal and nearly as large as apical disc.
- Primary spines stout, often flattened and becoming spatulate distally. One side usually rather smooth, with a fine ornament of small thorns, the other with a few strong coarse and serrated or thorned ribs. Neck and collar short.
Middle Jurassic (Aalenian) to Lower Cretaceous (Neocomian), Europe.
Cidaris orbignyana Agassiz, in Agassiz & Desor 1846, p. 28, by subsequent designation of Lambert & Thiery, 1910, p. 136. Syntype: Museum National d'Histoire Naturelle, Paris R06506.
- R. orbignyana (Agassiz, 1847); Kimmeridgian, Europe.
- R. fowleri (Wright, 1851); Aalenian, UK.
- R. copeoides (Agassiz in Agassiz & Desor, 1856); Bajocian-Oxfordian, France.
- R. guttata Cotteau, 1857; Callovian, France.
- R. nobilis (Munster in Goldfuss, 1826); Oxfordian-Kimmeridgian, Europe.
- R. maxima (Munster in Goldfuss, 1826); Oxfordian-Kimmeridgian, Europe.
- R. copeoides Agassiz & Desor, 1847; Bajocian to Callovian, France.
- R. tournali Desor, 1858; Neocomian, Franc.
|Classification and/or Status
Presumed paraphyletic by exclusion of Porocidaris and Fellius.
Beautifully illustrated by Radwanska (1999, 2003), who should be consulted for more information.
Desor, E. 1855-1858. Synopsis des echinides fossiles. Reinwald, Paris, 490 pp., 44 pls.
Radwanska, U. 1999. Lower Kimmeridgian echinoids of Poland. Acta Geologica Polonica 49 287-364, pls 1-49.
Radwanska, U. 2003. A monograph of the Polish Oxfordian echinoids. Part 1, Subclass Cidaroidea Claus, 1880. Acta Geologica Polonica 53, 143-165.