New psychropotid species (Echinodermata, Holothuroidea, Elasipodida) of the Western Pacific with phylogenetic analyses

Holothurians of the family Psychropotidae are widely distributed but remain the least studied deep-sea holothurians. On an expedition to the Western Pacific, six psychropotid specimens were collected by the Jiaolong Human Operated Vehicle (HOV). Through morphological examination, four of them were identified as a new species, Benthodytesjiaolongisp. nov., which was characterized as having minute papillae, a narrow brim, and a terminal anus; and the ossicles were rods and primary crosses. The remaining two specimens were identified as Psychropotesverrucicaudatus Xiao, Gong, Kou & Li, 2019, first recorded at the Kyushu-Palau Ridge. The phylogenetic analysis showed that B.jiaolongisp. nov. and P.verrucicaudatus were embedded in the clades Benthodytes and Psycheotrephes, respectively, and that Benthodytes was paraphyletic. The new species clustered with Benthodytessanguinolenta and was separated from the clade containing the other Benthodytes species.