Stellasteropsis Dollfus 1936

Dollfus 1936: 151; Macan 1938: 395; Clark and Rowe 1971: 32, 48; A.M. Clark 1993: 286 (as Stellasteropsis)

Roman & Strougo 1987: 36 (as Fayoumaster)

Diagnosis. Body stellate to strongly stellate, arms triangular, elongate, interradial arcs acute to curved. Skeleton robust, body covered by continuous granular cover. Abactinal plates extend along most of arms length, arm tips with abutting superomarginals in some species. Marginal plates wide, forming discrete border. Granules cover actinal and adambulacral plates. Other than furrow spines, no other adambulacral spines or accessories.

Comments. Stellasteropsis comprises at least three species occurring primarily in the western Indian Ocean, from the Suez Bay/Red Sea region to the eastern coast of South Africa. The type species, Stellasteropsis fouadi, displays significant morphological variation and is reported from a wide geographic range while the other two species are more poorly known and from fewer localities.

Although included in the Oreasteridae by Spencer and Wright (1966), most usage has placed Stellasteropsis within the Goniasteridae (e.g. Clark and Rowe 1971, A.M. Clark 1993). Characters observed on Stellasteropsis support a relationship with genera such as Stellaster and particularly Goniodiscaster. A tentative grouping of these genera is proposed below.

Stellasteropsis fouadi was described from the Gulf of Suez as the only member of the monotypic Stellasteropsis Dollfus, 1936. Subsequently, two species, Stellasteropsis colubrinus and Stellasteropsis tuberculiferus were described from the Arabian coast by Macan (1938). Distinctions between species as outlined by Macan (1938) and Clark and Rowe (1971) are based on the body shape, presence/absence of tubercles/spines on the distal inferomarginals and abactinal plates, marginal plate shape, pedicellariae, and variation in the distribution of granules. Clark and Rowe (1971) included only two species, S. colubrinus and S. fouadi in their key to Indo- Pacific asteroids, omitting S. tuberculiferus, which is included in the key herein.

Tubercles and/or spines appear to be present primarily in the Eocene Stellasteropsis pharaonum and in the Stellasteropsis species on the Arabian coast, particularly Stellasteropsis tuberculiferus and one form showing inferomarginal spines was observed on one specimen IE-2013-12596 from Madagascar.

Body morphology appears to be present as two main forms throughout Stellasteropsis ’ range, especially within S. fouadi, a broader disk, tapering arm form more similar to the holotype of S. fouadi, or a form with more elongate, narrower arms with smaller disk (e.g., IE-2007-1036). Although no clear pattern explains this variation, environmental factors and growth/size are likely important factors.

Synonymy and Relevance of Fayoumaster. Several characters are observed on both the holotype of Fayoumaster pharaonum Roman and Strougo (1987) and modern specimens, including the lectotype, of Stellasteropsis, which argue for synonymy of Fayoumaster Roman and Strougo 1987 within the latter Stellasteropsis Dollfus 1936. Stellate body form (R/r) for Fayoumaster was recorded as R/r=3.75 falls within the range of known Stellasterospsis species (R/r=2.0 to 3.9). Granular cover on Fayoumaster covers the superomarginal plate surface and is also continuous in Stellasteropsis. Body shape characters including broad interradial arcs, triangular arms with narrowing distalmost tips with an arched disk are also present in both. Both the carinal series on Fayoumaster and Stellasteropsis are polygonal and in a discrete series. Abactinal interradial plates are paired along each interradius such that the contact between the interradial abactinal plates is in direct alignment with adjacent, enlarged interradial superomarginal plates. Elongate superomarginal plates are also present on the arms of Fayoumaster and Stellasteropsis. Adambulacral plates in both Fayoumaster and Stellasterospis are rectangular but slightly more elongate in the former.

Roman and Strougo (1987) compared Fayoumaster with Stellaster and Goniodiscaster and recognized its affinities with these genera as well as with the Oreasteridae. Curiously however, their treatment either ignores or was ignorant of Stellasteropsis by Dollfus (1936).