Vertebrates from the basal horizons (Ypresian to Lutetian) of the Cucullaea I allomember, La Meseta Formation, Seymour (Marambio) Island, Antarctica.

M. REGUERO; C. TAMBUSSI; T. MÖRS; M. R. BUONO; S. MARENSSI; S. SANTILLANA

Edinburgh

Simposio; 11th International Symposium on Antarctic Earth Sciences; 2011

The University of Edinburgh, British Antartic Survey, British Geological Survey.

The La Meseta Formation contains one of the world´s most diverse assemblages of Eocene age, including terrestrial plants, marine invertebrates and marine as well as terrestrial vertebrates. The highly fossiliferous, lower horizons of the Cucullaea I Allomember of the La Meseta Formation are composed of poorly consolidated, marine sandstones and siltstones which were deposited in a coastal, deltaic and/or estuarine environment. Screen-washing of sediments collected from a single site, DPV 2/84 (64°14’21.782”S; 56°36’11.685”W), has produced hundreds of bone fragments and teeth of sharks, rays, chimaeroids, bony fishes, turtles, penguins, whales, and terrestrial mammals. The turtle material includes two marine taxa, including one species of Dermochelyidae. The shark fauna from this site is particularly diverse and includes species of Hexanchus, Squalus, Centrophorus, Pristiophorus, Squatina, Striatolamia, Odontaspis, Isurus, Carcharias, Cetorhinus, and Galeorhinus. The base of the Cucullaea I Allomember is correlated with the late Ypresian (49.5 Ma). We report about recent fieldwork on the site which produced a whale mandible that may represent a primitive archaeocete. The mandible bears two triangular, laterally compressed cheek teeth with multiple accessory denticles and wear facets characteristic of basilosaurids, i.e. Zygorhiza or Basilosaurus, but detailed comparisons with these taxa have yet to be made. We will give a description and preliminary classification of the specimen which probably represents the earliest record of whales in Antarctica.