MORPHOLOGICAL PHYLOGENY OF THE REEF CORAL FAMILY MEANDRINIDAE (ANTHOZOA, SCLERACTINIA)

Genetic phylogenies of Scleractinia are in stark contrast to traditional morphology-based systematics. Genetic analyses place Eusmilia, Rhizosmilia, and Phyllangia within Meandrinidae and remove Cnetella from Meandrinidae. This study uses SEM images and thin-sections to code skeletal morphology of extant and fossil species of Meandrina, Dichocoenia, Eusmilia, Dendrogyra, Goreaugyra, Placocyathus, Phyllangia, Rhizosmilia, and Oxysmila. Characters consist of traditional macromorphologic characters as well as newly conceived micromorphological and microstructural characters. The new characters treat coenosteum construction, coenosteum ornamentation, septal tooth morphology, septal tooth orientation, columella form, and columella development. Cladistic analyses place Dichocoenia basal to Eusmilia (Dendrogyra (Meandrina + Placocyathus) using Solenastrea as an outgroup. The monophyletic nature of Miocene to recent Dichocoenia is reaffirmed. These morphological results differ from molecular results primarily in the location of Dichocoenia, molecular results place Eusmilia basal to Dendrogyra (Dichocoenia + Meandrina). Intracolony variation in columella development is documented for one colony of Eusmilia fastigiata and provides the basis for character definition of columella shape and development, important in the coding of Atlantic Oxysmilia. Columella form that reaches the late lamellar plate stage and has a straight morphology is the pleisomorphic character state of Meandrinidae. The morphology of columella in earlier developmental stages has initially been important in grouping the azooanthellate genera Phyllangia, Rhizosmilia, and Atlantic Oxysmilia together. Fusiform crystals are grown along the lateral edge of the costae. They appear to have a conservative morphology within Meandrinidae. The use of fusiform crystal morphology is discussed for its potential use in higher-level coral systematics. This study lays the foundation to test whether other Pacific members of Meandrinidae are more closely related to their Caribbean congeners, or are more closely related to other Pacific corals.