Benthodytes tetrapapillata sp.nov.,a new elasipodid sea cucumber(Elasipodida:Psychropotidae)from a seamount in the Western Pacific Ocean

Benthodytes tetrapapillata sp.nov.was collected from a seamount located on the Caroline Ridge at a depth of 2 289 m,during the cruise of R/V Kexue in June 2019.We provided detailed descriptions of external and deposits morphology.The phylogenetic analyses based on cytochrome c oxidase Ⅰ(COI)and a concatenated dataset of 16S and COI genes showed that the new species belonged to Benthodytes that is not monophyletic.Both details of morphological comparisons and molecular analyses confirmed that Benthodytes tetrapapillata sp.nov.is a new psychropotid species.A state of main morphological characters in valid species of Benthodytes is also provided in this study.