Morphology and molecular phylogeny of three new deep-sea species of (Cnidaria, Octocorallia) from seamounts in the tropical Western Pacific Ocean.

Three new species of were discovered from seamounts in the tropical Western Pacific Ocean. sp. nov. and sp. nov. were collected from the Kocebu Guyot of the Magellan Seamount chain with the water depth of 1,821 m and 1,279-1,321 m, respectively, and sp. nov. was collected from a seamount adjacent to the Mariana Trench with the water depth of 298 m. They all belong to the "group A, Spiculosae" with rods distributed in body wall and tentacles, and differ from all congeners except Pante & Watling, 2012 by having a tree-shaped colony (vs. bottlebrush-shaped, planar or biflabellate). sp. nov. is unique in having a monopodial stem, the 1/3L branching sequence and the amoeba-shaped sclerites (sclerites branched toward to many directions) at the body bases of polyps. sp. nov. is most similar to , but differs by the regular 1/3L branching sequence and elongate flat scales in coenenchyme. sp. nov. is easily separated from congeners by the 1/4L branching sequence, the absence of sclerites in the basal body wall, and the very sparse scales in coenenchyme. Based on the phylogenetic and genetic distance analyses of mtMutS gene, all the available species were separated into two main groups: one includes , cf. and , which have two or more fans emerging from a short main stem (bi- or multi-flabellate colony); the other one includes all the species with the branching patterns as a single ascending spiral (clockwise or counterclockwise, bottlebrush-shaped colony), a fan (planar colony) and a bush of branches perched on top of a long straight stem (tree-shaped colony). Additionally, the tree-shaped colony represents a new branching pattern in , and therefore we extend the generic diagnosis.