Systematics of the coral genusCraterastrea(Cnidaria, Anthozoa, Scleractinia) and description of a new family through combined morphological and molecular analyses

The monotypic genus Craterastrea was assigned to the family Siderastreidae owing to the similarity of its septal micromorphology to that of Coscinaraea. Subsequently, it was synonymized with Leptoseris, family Agariciidae, based on corallum macromorphology. Since then, it has remained poorly studied and has been known only from a small number of specimens from relatively deep reef environments in the Red Sea and the Chagos archipelago, northern Indian Ocean. Access to museum collections enabled examination of type material and the recovery of coral skeletons from the Seychelles, Madagascar, and Mayotte, southern Indian Ocean. A recent survey in Mayotte allowed the in situ imaging of Craterastrea in shallow and turbid reef environments and sampling for molecular analyses. The molecular analyses were in agreement with the examination of micromorphology and microstructure of skeletons by revealing that Craterastrea levis, the only species in the genus, differs much from Leptoseris foliosa, with which it was synonymized. Moreover, Craterastrea is closely related to Coscinaraea, Horastrea and Anomastraea. However, these genera, currently ascribed to the Siderastreidae, are genetically distant to Siderastrea, the family's type genus, and Pseudosiderastrea. Hence, we restore the genus Craterastrea, describe the new family Coscinaraeidae due to its deep evolutionary divergence from the Siderastreidae, and provide revised diagnoses of the four genera in the family. The description of the new family Coscinaraeidae is a further step in the challenging but ongoing process of revision of the taxonomy of scleractinian corals as a result of the molecular systematics revolution.