Sibogaster Döderlein, 1924

Mah, Christopher L., 2024, New genera and species of deep-sea Goniasteridae (Asteroidea) from the North Pacific, Zootaxa 5543 (4), pp. 451-500 : 481

Sibogaster Döderlein, 1924

Sibogaster Döderlein 1924: 63 ; Mah 2016: 129

Diagnosis

Abactinal plates smooth, bare, weakly convex, round to polygonal in outline. Embedded glassy bosses present or absent. Marginal plates elongate, mostly smooth, bare ( S. digitatus has fewer than 6 granules on one or two interradial superomarginals). Inferomarginals adjacent to actinal surface covered with variably abundant granules. Actinal plates covered by granules. Adambulacral plates rectangular in shape. Furrow spines numerous, 6 to 15. Subambulacrals. thickened relative to furrow spines, remaining granulation identical to others on actinal surface.

Comments

Sibogaster includes 3 species, the low latitude tropical Pacific S. digitatus Döderlein, 1924 , the Atlantic S. bathyheuretor Mah, 2020 and the widely occurring S. nieseni Mah, 2016 , which have been recorded from 640 to 4175 m, but primarily from bathyal and abyssal depths (> 1000 m).

Mah (2016) observed morphological affinities with Plinthaster , Astroceramus and Pergamaster . Okeanosaster Mah 2022 also displays affinities with Sibogaster in that it shows smooth, bare abactinal and marginal plates-but with much smaller peripheral granules and lacking glassy granules embedded in the abactinal plate surface.