Mediaster Stimpson 1857: 530; Perrier 1894: 377; Verrill 1899: 178; Fisher 1911: 196; Verrill 1914: 295; 1915: 108; Fisher 1919: 255; Macan 1938: 369; H. L. Clark 1946: 83; Bernasconi 1963: 11; Halpern 1970: 202; Clark & Downey 1992: 251. (as Mediaster)
Comments. Mediaster includes 18 nominal species (A.M. Clark 1993, Mah 2015b) which occur in the Atlantic and Pacific Oceans and is among the earliest genera of starfishes described from the Pacific coast of North America (Stimpson 1857). Fisher (1911) reviewed two species present from the North Pacific, M. aequalis and M. tenellus and discussed taxonomic relationships among Atlantic and Pacific species. Carey (1972) subsequently discovered “ Mediaster elegans ” (= Bathyceramaster careyi n. sp) from deep-sea settings off the coast of Oregon.
Fisher (1911) pointed out the absence of the stellate radiating base, a defining characteristic of the genus, in the tropical East Pacific “ Mediaster elegans " Ludwig 1905 but did not undertake a revision of the group. During the course of this investigation both “ Mediaster elegans ” Ludwig 1905 and the species described by Carey (1972) as “ M. elegans ” were both found to be lacking the diagnostic synapomorphy for Mediaster and have since been reassigned to the new genus Bathyceramaster n. gen. (as above).