Marginaster Perrier 1881

Mah, Christopher L., 2023, New occurrence of Poraniidae (Valvatacea, Asteroidea) in Australia with a new genus and species from deep-sea settings, Memoirs of Museum Victoria 82, pp. 119-131 : 124

Marginaster Perrier 1881

Marginaster Perrier 1881: 16 .— 1884: 229.— Sladen 1889: 364.— Perrier 1894: 164–165.— Ludwig 1897: 189.— Verrill 1914: 18–19.— 1915: 75–76.— Downey 1973: 82.— Clark 1984: 25–27.— McKnight 2006: 106.

Cheilaster Bell 1893: 81 (superfluous replacement name for Marginaster Perrier )

Poranisca Verrill 1914: 19 .— Clark 1984: 25 [type: P. lepidus Verrill 1914 ]

Marginaster sp. McKnight 1968: 513.— Clark 1970: 5.— Clark and McKnight 2001: 166.

Type Species. Marginaster paucispinus Fisher 1913 (by subsequent designation)

Diagnostic comments. Marginaster has historically been considered a “provisional genus” ( Clark and Downey, 1992: 205), and as such most recent diagnoses ( Clark and Downey, 1992; McKnight, 2006) have been brief and incomplete. This account disagrees with prior accounts that assume Marginaster is a juvenile of other poraniid taxa, and as such, attempts to incorporate characters from known species, exclusive of Marginaster (now Bathymarginaster ) patriciae and the asterinid Marginaster (now Patiriella ) littoralis Dartnall 1970.

Diagnosis. Body small, R <2.5 cm, overall shape pentagonal to weakly stellate ( R /r=1.4–2.0). Body covered by variably thickened dermis, ranging from relatively thin ( Fig. 2a) to very thick and fleshy ( Fig. 2e, f). Abactinal plates reticulate, forming widely open papular regions between rod-like ossicles ( Fig. 2a, c, d). Plates variably with pointed, conical spinelets. Marginal plates wide, dorsal-facing, forming broad periphery ( Fig. 2a, c, d), each plate series bearing 2 –6 short spinelets. Inferomarginal spinelets flattened, larger than those on superomarginal plates. Actinal plates imbricate, tissue covered, relatively few overall ( Fig. 2b, d, f). One to three short, pointed furrow spines. One to three subambulacral spines.

Comments. Marginaster Perrier 1881 has been met with skepticism throughout its taxonomic history, beginning with Verrill (1914) and later with Downey (1973) and Clark and Downey (1992), who argued Marginaster is the juvenile or small form of a larger, possibly unknown, poraniid. Mah and Foltz (2014) argued that Marginaster is a separate but smallsized taxon, and that none of the North Atlantic genera or any of the known Southern Hemisphere poraniidae, such as Glabraster at comparable sizes, were morphologically consistent with Marginaster . No other known poraniids are distributed with a comparably occurring geographic and/or bathymetric distribution (Mah, unpublished data), making it seem unlikely that Marginaster is the juvenile form of some other Poraniidae .

Including B. patriciae , addressed herein, there are four known species: Marginaster capreensis ( Gasco, 1876) , M. paucispinus Fisher 1913 , and M. pectinatus Perrier, 1881 . Marginaster capreensis and M. pectinatus occur in the Mediterranean and the Atlantic, whereas M. paucispinus occurs in the Pacific and the Indian Ocean ( Reunion Island). Although a comprehensive generic review is beyond the scope of the present study, cursory examination suggests relatively few character differences among species, particularly of inferomarginal spine number and marginal plate number, expression of the reticulate abactinal skeleton and abactinal spination.