Abstract
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.
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