Family Euryalidae Gray, 1840

Type genus

Euryale Lamarck, 1816 (type species: E. aspera Lamarck, 1816).

Other genera

Asteromorpha Lütken, 1869, Asteroschema Örstedt & Lütken, 1856, Asterostegus Mortensen, 1933 a, Astrobrachion Döderlein, 1927, Astroceras Lyman, 1879, Astrocharis Koehler, 1904, Ophiocreas Lyman, 1869, Squamophis Okanishi et al. 2011, Sthenocephalus Koehler, 1898, Trichaster Agassiz, 1836 .

Diagnosis

Dorsal disc with thickened skin and embedded external ossicles. Single column of teeth, dental plate fragmented. Arms branching in Euryale, Trichaster and Sthenocephalus . Distal vertebrae with oral bridge in Asteromorpha, Asterostegus, Astrobrachion, Astroceras, Euryale, Sthenocephalus and Trichaster (Okanishi et al. 2011 b) . Gonads may extend into the arms. Arm spine articulation with large muscle opening separated from the nerve opening by a large, swollen ridge.