New coral-bivalve association (Actinastrea-Lithophaga) from the Eocene of Florida

Abstract

The endolithic mytilid bivalve, Lithophaga palmerae n. sp., from the Upper Eocene Ocala Limestone of north-central Florida, sheds new light on the evolution of lithophagids with its unspecialized morphology and highly specialized mode of life. Lithophaga palmerae n. sp. inhabited dead and living coral as indicated by orientation evidence. In living coral, the anterior end of the borehole was sealed off with thick, continuous, “false floors” of CaCO3, as the posterior end was extended to keep pace with coral growth. To date, this new species of lithophagid has been found associated with only one host coral, Actinastrea cf. A. incrustans (Duncan). Association with living coral is found today in L. bisulcata (d'Orbigny) and L. dixonae Scott from the Caribbean and in several Red Sea and Indo-Pacific lithophagids. In the fossil record, live-coral boring has been reported from the Miocene of the Vienna Basin of Austria and from the Pleistocene of Grand Cayman Island in the Caribbean. Lithophaga palmerae n. sp. provides a valuable ancestral link in the evolution of Lithophaga by extending the range of live-coral boring back to the Eocene of Florida.