EARLIER (LATE PLIOCENE) FIRST APPEARANCE OF THE CARIBBEAN REEF-BUILDING CORAL ACROPORA-PALMATA - STRATIGRAPHIC AND EVOLUTIONARY IMPLICATIONS

An integrated stratigraphic study of reefal deposits on the Caribbean side of the Isthmus of Panama (Limon, Costa Rica) has discovered a sig nificantly earlier first appearance of the major reef-building coral A cropora palmata, A. palmata is here reported from the early late Plioc ene, constrained in age to within the Gauss chron (ca. 3.6-2.6 Ma), Th is coral was previously thought to have originated in the earliest Ple istocene and has subsequently been used as a Quaternary marker through out the Caribbean and the Bahamas. An earlier appearance in the southe rn Caribbean implies a diachronous first appearance datum relative to the northern Caribbean, This older age also places A. palmata well wit hin the transition phase of a Pliocene (4-1 Ma) faunal turnover that w as marked by widespread extinction and origination of Caribbean coral species. An early late Pliocene origination is coincident with formati on of the Isthmus, climate reorganization, and frequent sea-level chan ges associated with onset of Northern Hemisphere glaciations, The rapi d growth and accumulation rates that characterize A. palmata may there fore be adaptive to these fluctuating environmental conditions, enabli ng its success during the subsequent Pleistocene glacial cycles.