Evolution & Systematics

Phylum Echinodermata
Class Ophiuroidea
Order Ophiurida
Family Ophiactidae
Genus Ophiactis
Species Ophiactis savignyi


Class Ophiuroidea is split into two orders: Order Euryalida (containing snake stars and basket stars) and Order Ophiurida (containing brittle stars; Stohr et al. 2012). The classification from the family level down to the species level is based on morphological traits, as well as some ecological traits (Smith et al. 1995). However, the Ophiuroid classification system is still not universally accepted, as our understanding of Ophiuroids is still quite limited (Smith et al. 1995; Stohr et al. 2012). 

Within Phylum Echinodermata, Ophiuroids are related more closely to asteroids (Smith et al. 1995). Class Ophiuroidea radiated during a relatively short period of time between the late Palaeozoic and early Mesozoic, particularly towards the end of the Permian (Stohr et al. 2012). The fossil record of Ophiuroids extends back to the early Ordovician, approximately 500 million years ago (Smith et al. 1995).