A new species in the genus <i>Styracaster</i> (Echinodermata: Asteroidea: Porcellanasteridae) from hadal depth of the Yap Trench in the western Pacific.

Styracaster yapensis sp. nov. is reported from the Yap Trench in the western Pacific from hadal depths between 6377-6575 m, which is among the deepest known occurrence of a species in this genus. It is distinguished from other Styracaster species by its abactinal surface armature and rudimentary cribriform organs. This paper provides a description of the new species along with detailed photos. The intraspecific differences between the holotype and paratype of the new species are examined with molecular and morphological approaches.