Phylogenetics and taxonomy of the scleractinian coral family Euphylliidae

The family Euphylliidae consists of reef-building zooxanthellate scleractinian corals distributed across the Indo-Pacific. Seven extant genera comprising a total of 22 valid species are currently recognised. Recent studies have re-organised the taxonomy of the family at the genus level based on molecular and morphological data, including a comprehensive revision of Euphyllia and the resurrection of Fimbriaphyllia. Here, three mitochondrial loci (coi, 12S rRNA, and 16S rRNA) were sequenced and morphological examinations were conducted at three scales (macro/micromorphology and microstructure of the skeleton, and polyp morphology) to study the phylogeny and taxonomy of Euphylliidae. We analysed a total of 11 valid species collected from seven Indo-Pacific localities. The monotypic genus Coeloseris, currently in Agariciidae, was also investigated since previous molecular data suggested a close relationship with the Euphylliidae. Molecular and morphological phylogenetic trees were broadly concordant in the definition of genus-level clades. All analysed genera, i.e., Ctenella, Euphyllia, Fimbriaphyllia, Galaxea, and Gyrosmilia, were reciprocally monophyletic based on molecular results. Coeloseris was nested within the family and, therefore, is formally moved into Euphylliidae. Updated morphological diagnoses are provided for each investigated genus. This study further demonstrated that a phylogenetic classification of scleractinian corals can be achieved by applying a combined morpho-molecular approach. Finally, we encourage phylogenetic and taxonomic studies of the euphylliid taxa not yet analysed molecularly, such as the monotypic genera Montigyra and Simplastrea.