A coral among stars: A new octocoral family (Anthozoa, Octocorallia, Malacalcyonacea) from seamounts in the tropical eastern Pacific

Existing studies highlight the remarkable diversity of life forms inhabiting deep-sea environments, despite the extreme conditions that characterize them. Here, a new family of gorgonian octocorals is described using an integrative taxonomic approach, combining morphological and genetic evidence. The organisms were obtained from seamounts off the insular shelf of Isla del Coco and three geological features of the Costa Rica Pacific margin, during two expeditions using the ROV SuBastian at depths of 360– 529 m.

Laurinqueidae fam. nov. is characterized by large irregular-flabellate colonies, with branching that is irregularly lateral, dense, and occasionally anastomosing. Thin coenenchyme includes a sclerome composed of rods and spindles with simple or complex tubercles; the axial sheath has rods and radiates. Polyps are tubular and conspicuously elongated, partially retractile into short cylindrical or dome-shaped mounds and arranged all around the branches.

The anthocodiae have tuberculate rods and spindles arranged as points and an inconspicuous collaret. Colonies are bright yellow when alive. Phylogenetic analysis of two mitochondrial genes, mtMutS and COI, and the nuclear 28 S rDNA did not clarify the position of the taxon, with each single-gene marker placing it in a different family.

Phylogenomic analysis of ultraconserved elements and exons strongly supports its placement in a unique clade, sister to Eunicellidae. The colony growth form and sclerome differ markedly from members of that family. Herein we describe Laurinque elenya gen. et sp. nov. and place this unique lineage in the new family Laurinqueidae fam. nov.

This study highlights the extreme incongruence among single-marker gene trees and the need for phylogenomic analyses based on hundreds of genes to elucidate the relationships among deeply divergent lineages of octocorals.