Title: A new family of stoloniferous coral (Octocorallia: Malacalcyonacea) from the Irish Continental Margin, Northeast Atlantic

The deep-sea harbours diverse benthic communities of octocorals that are rarely identified to species rank, in part due to a lack of expertise and the large amount of undescribed diversity. Even in relatively well-studied areas, such as the Irish Margin in the Northeast Atlantic, new species are still being discovered. However, many of these species are large charismatic arborescent colonies. Herein we describe a new family and genus of stoloniferous coral from the Porcupine Seabight, using an integrated approach of traditional taxonomy and Ultraconserved Elements (UCEs). Primafloridae fam. nov. and Primaflorus gen. nov. has fully retractile polyps, and sclerites in the form of rods, spindles, and boomerangs in both the stolon and polyps, with irregularly shaped plates found in just the tentacles. All sclerites are tuberculated to varying degrees. One species is described, Primaflorus maxwelli gen. nov. sp. nov., from scleractinian rubble habitat at 696 to 746 m from the Irish Continental Margin, just outside the Hovland Mound Special Area of Conservation. Genome skim libraries were sequenced and UCEs, complete mitogenomes, and partial 28S rRNAs were extracted. Phylogenomic inferences constructed from UCEs recovered the Primafloridae fam. nov. within subordinal Clade M2 of Order Malacalcyonacea, specifically as a sister lineage to a subclade comprising Families Cerveridae and Melithaeidae. The sclerome and lack of a central axis of P. maxwelli gen. nov. sp. nov., are sufficient to distinguish P. maxwelli gen. nov. sp. nov., from members of both of those families.