Clade Diadematacea Duncan 1889
Full reference: P. M. Duncan. 1889. A revision of the genera and great groups of the Echinoidea. Journal of the Linnean Society, Zoology 23:1-311
Parent taxon: Euechinoidea according to A. B. Smith 1995
See also Durham and Melville 1957 and Fell 1966
Sister taxa: Acroechinoidea, Echinacea, Echinothurioida, Galeroclypeus, Loriolella, Serpianotiaroida, Triadocidaridae, Triadotiaroida
Subtaxa: Pygasteroida
Distribution: found only at Crystal River Limestone (Eocene of Florida)