†order Plesiocidaroida Duncan 1889 (sea urchin)
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: Echinacea according to H. B. Fell and D. L. Pawson 1966
Sister taxa: Arbacioida, Besairecidaris, Bramus, Camarodonta, Crinocidaris, Glyphopneustidae, Orthopsida, Stomopneustoida
Subtaxa: Tiarechinidae
Ecology: slow-moving low-level epifaunal grazer