Redescription of the type material of Clavularia de Blainville, 1830 (Anthozoa: Octocorallia), with descriptions of new taxa and a new family.

The taxonomy of soft corals with a stoloniferous growth form is challenging. The family Clavulariidae and, more specifically, the genus Clavularia have acted as a repository for most stoloniferous corals that could not systematically be differentiated with morphology. In addition, the lack of morphological and genetic data for the type species of Clavularia, Clavularia viridis, has made a revision of the genus impossible. In this study, we use an integrative taxonomic approach combining morphological examinations and novel molecular methods to revise the taxonomy and systematics of Clavulariidae within Octocorallia. We re-describe key species of Clavularia, including C. viridis, C. inflata and C. koellikeri, resolve the position of Clavulariidae within Octocorallia, and present a revised taxonomy of the tropical, zooxanthellate species of Clavularia that includes morphological characters of each species. We further confirm the polyphyly of Clavulariidae, and resurrect the genus Hicksonia and family Hicksoniidae (Malacalcyonacea) to accommodate a new species with connecting tubes on multiple levels (H. tohrui sp. nov.). We also describe a new genus and species of Clavulariidae from Japan Bairdium iriomotejimaensis gen. nov., sp. nov. and a new Clavularia species from the Great Barrier Reef (C. brunafolia sp. nov.). This study resolves the fundamental taxonomy of Clavularia, and provides the necessary baseline for future works. ZooBank: urn:lsid:zoobank.org:pub:61754CF6-A3C9-4D1C-AC6F-4435C12BD4AD.