The Echinoid Directory

Order Echinothurioida Claus, 1880

Diagnosis	Regular euechinoids with: monocyclic apical disc in adults lantern with grooved teeth ambulacral plates continue onto the peristome forming regular series ambulacral plates pseudocompound, with large primary element and two demiplates coronal plates thin and with imbricate sutures primary tubercles perforate spines hollow.
Range	Middle Jurassic (Bajocian) to Recent; worldwide.
Species Included	Includes the families Kamptosomatidae, Echinothuriidae Pelanechinidae and Phormosomatidae
Remarks	Echinothurioids have grooved teeth and a monocyclic apical disc like diadematoids but can be distinguished from that clade by having ambulacral plates continuing across the peristome membrane. Most have non-crenulate tubercles. Claus, C. F. W. 1880. Grundzüge der Zoologie. 4th ed. N. G. Elwert´sche Universitätsbuchhandlung, Marburg & Leipzig, vol. 1: vii+821 pp., vol. 2: iv+522 pp. Mortensen, T. 1935. A Monograph of the Echinoidea. II. Bothriocidaroida, Melonechinoida, Lepidocentroida, and Stirodonta. C. A. Reitzel, Copenhagen, 647 pp.