Eocene whales from La Meseta Formation, Marambio (=Seymour) Island, Antarctica

M. R. BUONO; M. S. FERNÁNDEZ; M. REGUERO

Simposio; XII International Symposium on Antarctic Earth Science (ISAES 2015); 2015

The La Meseta Formation, Marambio (=Seymour) Island, NE Antarctic Peninsula, (Antarctica) is one of the world's most diverse fossil assemblages of Eocene age which has produced marine and terrestrial mammals. The cetacean fossil record includes specimens of the paraphyletic group of basal whales Archaeoceti, and the oldest archaic toothed mysticete, Llanocetus denticrenatus. All these specimens were collected from Cucullaea I allomembers of the La Meseta Formation and Submeseta Formation (Middle-Late Eocene). In particular, archaeocete records are based on nonspecific material collected in the upper levels of the La Meseta Formation and they were tentatively assigned to Basilosauridae. However, some authors suggest that these materials are too fragmentary to be confidently assigned to family level. During the last thirty years the prospecting field work in La Meseta and Submeseta Formations of Marambio Island, organized by the Direccion Nacional del Antártico ? Instituto Antártico Argentino and Museo de La Plata, resulted in the collection of several new cetaceans remains. The goal of this study is carry out a revision of the antarctic cetaceans deposited in the vertebrate paleontology collection of Museo de La Plata in order to resolve the taxonomic status of this specimens and thereby gain a better understanding of the cetaceans diversity during the Eocene in the Peninsula Antarctica. Specimens recovered from the La Meseta Fm. (early-middle Eocene) could only be identified as Cetacea indet. On the contrary, four specimens (represented by isolated cheek teeth and incisor, an incomplete left mandible, a vertebra, and an innominate pelvic bone, respectively) recovered from the Submeseta Fm. (late Eocene) can be confidentially referred to Basilosauridae. These results suggest that the global dispersion of basilosaurids occurred at the earliest stages of their evolutionary history.