Morphology and phylogenetic analysis of five deep-sea golden gorgonians (Cnidaria, Octocorallia, Chrysogorgiidae) in the Western Pacific Ocean, with the description of a new species.

Explorations of seamounts in the Western Pacific Ocean and South China Sea resulted in collecting 18 specimens of golden gorgonians. Based on the morphology and the genetic analysis of mtMutS, they are described as one new species, , and four known species, including Xu, Zhan & Xu, 2020, (Wright & Studer, 1889), Kükenthal, 1919, and Pante & France, 2010. belongs to the "group A, Spiculosae" with rods or spindles distributed in the polyp-body wall and tentacles, and differs from all of its congeners except by the 1/3L branching sequence and amoeba-shaped sclerites at the basal polyp body. The mtMutS sequence of has six deletion mutations compared to those of its congeners, supporting the establishment of the new species. Although no genetic variability was observed between the closely related species and Pante & Watling, 2012, the former is different from the latter by the apparently irregular sclerites in the polyp body wall. The two specimens of match well with the original description except for relatively larger polyps, while the specimens have slightly smaller polyps than the holotype. The juvenile of has an obvious morphological difference with the adults in the colony shape and branches, but they can be unified by the same polyps and sclerites as well as mitochondrial MutS sequences. Thus, the generic diagnosis of is slightly extended to include the morphology of juveniles. The morphology of Pante & France, 2010, as a new record for the South China Sea, matches well with that of the original description. In the phylogenetic trees, the species are separated into two clades, and while and formed a sister clade.