California Sun Star

It resembles closely Pycnopodia Stimpson, but differing in having a smaller disk, with the rays constricted at the base and easily detachable. In the entire absence of rudimentary annular or calcareous ridges at the base of the ray, in the abortion of alternate supermarginal plates beyond the base of the ray, and in the small widely spaced inferomarginals each bearing a slender spine; in the greater prominence of the adambulacral plates which are placed on the same level with the inferomarginals (and each with a single spine as in Pycnopodia); in the less crowded condition of the ambulacral ossicles.

Rathbunaster californicus lives along the west coast of North America from southern California to southern Alaska. It is found in muddy substrates in deep ocean/benthic environments and has been found at depths of 60 and 1,000 m below the surface off of California and depths from 99 to 768 m off the coast from the Puget Sound to Alaska.

Rathbunaster californicus is a carnivore and detritivore, feeding on crustaceans, worms, detritus, and fish using pincers on its aboral side. Because the majority of its prey is benthic, sediment is found in the stomach. One of the main decomposers in the deep ocean, it has been observed assisting in the decomposition of whale carcasses in the Monterey Canyon. The stomach has strong digestive enzymes, and R. californicus can start digesting food before it even enters its digestive system. The short digestive glands extend into the arms.