Edrioasteroidea

Edrioasteroids Temporal range: Middle Cambrian–Early Permian PreꞒ Ꞓ O S D C P T J K Pg N Possible Ediacaran occurrence
Streptaster vorticellatus (13 mm across) from the Upper Ordovician of Kentucky, USA
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Echinodermata
Subphylum:	Crinozoa
Class:	†Edrioasteroidea Billings 1858
Genera
See text

Edrioasteroidea is an extinct class of echinoderms. The living animal would have resembled a pentamerously symmetrical disc or cushion. They were obligate encrusters and attached themselves to inorganic or biologic hard substrates (frequently hardgrounds or brachiopods).^[1] A 507 million years old species, Totiglobus spencensis, is actually the first known echinoderm adapted to live on a hard surface after the soft microbial mats that covered the seafloor were destroyed in the Cambrian substrate revolution.^[2]

The oldest undisputed fossils of Edrioasteroidea are known from Cambrian (Stage 3, about 515-520 Ma ago) of Laurentia and are among the oldest known fossils of echinoderms. Some authors propose that an enigmatic Ediacaran (about 600 Ma) organism Arkarua is also an edrioasteroid, but this interpretation did not gain wide acceptance.^[3] Last edrioasteroids are known from Permian (Late Kungurian, about 270-280 Ma).^[4]