Order Ophiurida Müller & Troschel, 1840, restricted sensu O’Hara et al. (2017)

Diagnosis

Arms never branching. Spine articulation with muscle opening generally surrounded by ridges and/or knobs and separated from nerve opening by vertical ridge, lateral arm plates generally with external ornamentation (tubercles, striation, spurs). Strong influence of paedomorphosis (Stöhr & Martynov 2016).