Tosia (Ceramaster) Verrill, 1899: 161
Ceramaster Fisher, 1906: 1054; 1911: 162, 204; Verrill, 1914: 289; Koehler, 1924: 173; Mortensen, 1927: 80; Djakonov, 1950: 38; Tortonese & A.M. Clark, 1956: 347; Halpern, 1970 b: 62; 1970 c: 212; 1970: 62; Downey, 1973: 49; McKnight, 1973: 178; Downey, 1973: 49; A.M. Clark & Courtman-Stock, 1976: 61; Clark & Downey, 1992: 231; Downey in Clark & Downey, 1992: 231
Philonaster Koehler, 1909: 78 [type species Pentagonaster (Philonaster) mortenseni Koehler, 1909]
Tosiaster Verrill, 1914
Diagnosis. (See comments below). Body outline pentagonal in most (i.e., R/r= 1.1 to 1.5) with some becoming more stellate. Abactinal plates tabulate, granules present on abactinal plates, marginals, actinal plates. Fasciolar grooves present among abactinal, marginal plates. Bare “patch” on dorsal facing of superomarginal plates.
Comments. The genus Ceramaster includes 17 nominal species from the Arctic, Atlantic, Indian, and Pacific oceans (A.M. Clark, 1993) but has never undergone a comprehensive, global revision. Ceramaster also displays morphological overlap with other similar goniasterid genera, such as Peltaster (Clark and Downey, 1992; Halpern, 1970 b) which further confuses boundaries between the two genera and among species in each genus. As a consequence, it is unlikely that Ceramaster is monophyletic. Comprehensive diagnosis of Ceramaster is beyond the scope of the regional treatment here and so, only an abbreviated, functional definition of Ceramaster is outlined above.
Ceramaster includes many nominal species, such as Ceramaster patagonicus, Ceramaster grenadensis, and Ceramaster granularis that display morphological intergradation with few discrete differences. For example, nominal C. patagonicus occurs in both the Northern and Southern Hemisphere, ranging from boreal waters in the North pacific to subantarctic waters in the South Pacific (New Zealand and southern Australia). This is a pattern similar to that of the goniasterid Hippasteria (Mah et al, 2010).
Revisionary efforts within Ceramaster have not met with universal acceptance. Clark and Downey (1992) presented Ceramaster patagonicus as a subspecies within the C. grenadensis species complex in contrast to O’Hara (1998) and H.E.S. Clark & McKnight (2001) who have argued C. patagonicus as a distinct complex of species.