Species Diversity 25: 183–188 Published online 8 August 2020 DOI: 10.12782/specdiv.25.183 A New Species of Bathyal Nemertean, Proamphiporus kaimeiae sp. nov., off Tohoku, Japan, and Molecular Systematics of the Genus (Nemertea: Monostilifera) Natsumi Hookabe1,2,5, Shinji Tsuchida3, Yoshihiro Fujiwara3, and Hiroshi Kajihara4 1 Graduate School of Science, Hokkaido University, Sapporo, Hokkaido 060-0810, Japan E-mail:
[email protected] 2 Present address: Misaki Marine Biological Station, School of Science, The University of Tokyo, Miura, Kanagawa 238-0225, Japan E-mail:
[email protected] 3 Japan Agency for Marine-Earth Science and Technology, Yokosuka, Kanagawa 237-0061, Japan 4 Faculty of Science, Hokkaido University, Sapporo, Hokkaido 060-0810, Japan 5 Corresponding author (Received 21 October 2019; Accepted 15 April 2020) http://zoobank.org/71D0D145-2CE7-4592-BD82-C67EAA0A41E5 The monostiliferous hoplonemertean Proamphiporus kaimeiae sp. nov. is described based on a single specimen collect- ed from the bottom of the Northwest Pacific, 262 m deep, off Tohoku in Japan, by use of a remotely operated vehicle during a cruise organized by Tohoku Ecosystem-Associated Marine Sciences (TEAMS) research project in 2019. The position of the cerebral organs in the new species, being posterior to the proboscis insertion, is unusual for Eumonostilifera, which is one of the diagnostic traits of the so-far monospecific Proamphiporus Chernyshev and Polyakova, 2019, and Amphiporus rectangulus Strand, Herrera-Bachiller, Nygren, and Kånneby, 2014. The latter is herein transferred to Proamphiporus to yield a new combination, Proamphiporus rectangulus comb. nov., based on the reported internal morphology. Molecular phylo- genetic analyses based on 16S rRNA, cytochrome c oxidase subunit I, 18S rRNA, 28S rRNA, and histone H3 genes placed P.