Article: Systematics of the Oligocene to Miocene reef coral Tarbellastraea in the northern Mediterranean
Ann F. Budd, Francesca R. Bosellini and Thomas A. Stemann
Multivariate statistical analyses are used to distinguish species of the common reef-building coral Tarbellastraea at Oligocene and Miocene localities within the Aquitaine Basin, western Mediterranean, and central Paratethys regions; and to trace their distributions through geological time. Thirteen measurements or counts are made on thin sections of 126 colonies collected at 13 widely scattered localities, whose geological ages are newly updated. The data are analysed using average linkage cluster analysis and canonical discriminant analysis to distinguish clusters of colonies representing morphometric species. Names are assigned by qualitatively comparing measurements on the statistically recognized species with those of primary types of all previously described species of Tarbellastraea.The results show that Tarbellastraea originated during the Oligocene (Rupelian) and became extinct during the Early Messinian. A total of 12 species (including two new species from the Italian Oligocene, and two species described previously as varieties) lived in the investigated areas during Oligocene and Miocene time. Except during the Oligocene, all but one species (T. ellisiana) were widespread. Although species richness within the genus remained constant at 5-7 species throughout much of its stratigraphical range, morphological disparity decreased significantly through time. The observed constancy in richness contrasts with the decrease reported overall in the Mediterranean reef coral fauna. Species originations were highest during the Burdigalian, when temperatures across the region increased. Species extinctions remained constant until the latest Miocene, when the extinction rate increased as cold Atlantic waters entered the Mediterranean.New species described are Tarbellastraea bragai, T. chevalieri, T. russoi and T. salentinensis.