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 and Downey 1992: 251; A.M. Clark 1993: 262 (checklist); Rowe & Gates 1995: 65 (checklist); H.E.S. Clark & McKnight 2001: 69; Mah 2016: 118 (as Mediaster)
Verrill 1894: 257 (as Isaster)
Diagnosis. Goniasterid genus with tabulate abactinal plates displaying internally radiating ossicles from base of each plate. Abactinal tabulae plates with granules or spinelets. Abactinal plates in most, extending to arm tip, but exceptionally with distalmost superomarginals abutting. Abactinal, marginal, actinal surface covered by granules.
Comments. Mediaste r includes 15 species, two in the Atlantic, 10 in the Pacific, one South African species and one from the Indian Ocean (A.M. Clark 1993). One species, Mediaster ornatus, is widespread and occurs in both the Indian and Pacific Oceans (Macan, 1938). Mah (2016) reassigned “ Mediaster ” elegans to Bathyceramaster owing to the absence of a stellate radiating base, which has been historically identified as a synapomorphy for Mediaster.
Two species, Mediaster ornatus and Mediaster murrayi have been historically recorded from the Indian Ocean as documented by Macan (1938). Brief descriptions of these species are included herein for convenience and completeness. Three new species from Indian Ocean are included.