According to Mortensen (1928) the only character that distinguishes Eurocidaris from Ctenocidaris is that its oral primary spines are simple and undifferentiated; those of Ctenocidaris being decidedly serrate and spear-shaped. Aporocidaris has a significantly larger apical disc and Rhynchocidaris has a characteristic triple pore structure adorally and clavate secondary spines. However, the differences between these taxa is pretty minimal and probably does not merit separation at genus level.
Smith & Jeffery (2000) tentatively assign certain interambulacral plates from the Palaeocene to this genus on the basis of their tuberculation.
Mortensen, T. 1928. A monograph of the Echinoidea. 1, Cidaroidea. C. A. Reitzel, Copenhagen.
McKnight, D. G. 1974. Some echinoids new to New Zealand. NZOI Records 2, 25-44.
Smith, A. B. & Jeffery, C. H. 2000. Maastrichtian and Palaeocene echinoids: a key to world faunas. Special Papers in Palaeontology 63, 1-406.