Hippasteria

Clark, Roger N. & Jewett, Stephen C., 2011, A new sea star of the genus Hippasteria (Asteroidea: Goniasteridae) from the Aleutian Islands, Zootaxa 2963, pp. 48-54 : 53

Key to the genus Hippasteria in the Aleutian Islands

1a Marginal plates oblong, oval or elliptical, bearing a single slender tapering spine at the center, often flanked on either side by short tubercles; actinal and abactinal plates often extending between marginals; abactinal and marginal plates encircled by small rugose or denticulate granules; abactinal pedicellaria numerous, relatively small, base broader than apex...................................................................................................... H. californica

1b Actinal and abactinal plates not extending between marginal plates; marginal plates more or less quadrate; granules encircling abactinal and marginal plates not rugose or denticulate........................................................ 2

2a Abactinal surface profusely covered with large, low, long, bivalve pedicellaria and short, blunt conical spines and tubercles; surface of marginal plates bearing 1–2 thick, blunt conical spines, variously sized conical tubercles and frequently one large, low bivalve pedicellaria. Color uniformly white or cream............................................... H. heathi

2b Surface of marginal plates lacking large, low bivalve pedicellaria and/or numerous conical spines and tubercles. Color redorange abactinally..................................................................................... 3

3a Granules encircling abactinal and marginal plates pointed, usually with sharp apical projection; furrow spines slightly to strongly compressed (oval to flattened in cross-section)....................................................... 4

3b Granules encircling abactinal and marginal plates low, smooth, rounded or oval; furrow spines cylindrical or sub-cylindrical (tapering), round in cross-section......................................................................... 5

4a Abactinal and marginal plates bearing rather stout, tapering spines; granules encircling plates usually broad, flattened, triangular; a few marginals usually bearing a single small pedicellaria (slightly taller than long); adambulacral plates bearing two strongly compressed furrow spines, and a single shorter, thick, blunt subadambulacral spine (or sometimes a large bivalve pedicellaria)................................................................................. H. kurilensis

4b Abactinal and marginal plates bearing short, thick, blunt cylindrical or inflated spines; abactinal surface bearing numerous bivalve pedicellaria; granules encircling abactinal plates well spaced, often quite elongated; adambulacral plates bearing two blunt, somewhat compressed spines; adoral spine often reduced, much shorter, and only half as thick as aboral spine, and a single short, thick, blunt subadambulacral spine and some thick, blunt, flattened tubercles.............. .. H. aleutica sp. nov.

5a Abactinal and marginal plates bearing 1–2 short, stout, tapering spines or tubercles; abactinal surface profusely covered with relatively small, bivalve pedicellaria; several marginal plates typically bearing a single bivalve pedicellaria; adambulacrals bearing 1–2 thick, blunt tapering, cylindrical furrow spines and one or two similar but shorter subadambulacral spines................................................................................................... H. armata

5b Abactinal and marginal plates bearing slender, tapering spines (up to 5 on some marginals); encircling granules small (often spaced), smooth; marginal plates very rarely (if ever) bearing any pedicellaria; adambulacral plates with typically two relatively long, tapering furrow spines and a single similar subadambulacral spine............................. H. spinosa