Revision of Oligocene Mediterranean meandroid corals in the scleractinian families Mussidae, Merulinidae and Lobophylliidae
Traditional morphology-based systematics indicates close evolutionary relationships between Caribbean and Indo-Pacific ‘faviid’ and ‘mussid’ reef corals. However, molecular phylogenies reveal three distinct family-level clades, which diverged by middle Eocene time: (1) Caribbean faviids + mussids; (2) Indo-Pacific faviids; and (3) Indo-Pacific mussids. During the early Cenozoic, members of these clades also occurred in a third geographical region, the Mediterranean, but became extinct in that region during the Miocene, as the Tethys broke up. We perform morphological phylogenetic analyses including Caribbean, Indo-Pacific and Mediterranean Oligocene and Recent taxa to reconstruct the pattern of divergence between the three regions, and examine how it was related to biogeography. First, fossil specimens were selected from museum collections, and a total of 13 species (three of which are new) were distinguished using nine morphological features. These 13 species were then added to a dataset with taxa consisting of 62 Recent plus one additional extinct species, and with 50 characters. In addition to traditional macromorphology, the characters include new micromorphological and microstructural features observed using electron microscopy and transverse thin sections. Phylogenetic analysis was performed on the dataset using parsimony. The results show that, contrary to traditional systematics, 11 of the 13 Mediterranean extinct coral species group more closely with Indo-Pacific taxa than they do with Caribbean taxa. Recent Caribbean taxa and Indo-Pacific ‘mussids’ form distinct clades; but Indo-Pacific ‘faviids’ form four poorly resolved subclades basal to the Caribbean clade. These results suggest that Mediterranean meandroid corals belong to a cosmopolitan pantropical fauna, from which modern Caribbean meandroid corals diverged as the Caribbean became isolated. Phylogenetic analyses including fossils have higher resolution than analyses including only modern corals. The systematics of the 13 extinct species are formally revised. Two new species – Variabilifavia ausuganensis sp. nov. and Echinophyllia sassellensis sp. nov. – and one new genus – Paraleptoria gen. nov. – are named, and one undescribed species is left in open nomenclature. Two previously synonymized genera are resurrected.