Fossil Dugongidae (Mammalia, Sirenia) from the Paraná Formation (late Miocene) of Entre Ríos Province, Argentina

VÉLEZ-JUARBE JORGE; NORIEGA JORGE IGNACIO; FERRERO BRENDA SOLEDAD

AMEGHINIANA

ASOCIACION PALEONTOLOGICA ARGENTINA

Lugar: Buenos Aires; Año: 2012 vol. 49 p. 585 - 593

0002-7014

Fossil sirenians are well known from the Western Atlantic and Caribbean (WAC) region. Neogene records from the Atlantic coast of South America, although scarcer, seem to reflect a similar taxonomic composition to its northern contemporaries. Fossil sirenians from Argentina are known from the late Miocene Paraná and Ituzaingó formations in Entre Ríos Province. An upper third molar deposited at the Museo de Paleontología de la Universidad Nacional de Córdoba. (CORD-PZ 4301), from the Paraná Fm., was originally described and assigned to the dugongid genus Metaxytherium de Christol. Subsequent workers suggested it could instead belong to the dugongid genus Dioplotherium Cope; a designation which we confirmed upon examination of the material. Additionally we describe new sirenian remains from the Paraná Fm., consisting of two incomplete maxillae with teeth belonging to one individual deposited at the Museo de Ciencias Naturales de Paraná (MASP). This specimen shows similarities with species of Metaxytherium from the northern WAC. The Paraná Fm. sirenians represent the southernmost occurrences of these two genera, and the geologically youngest occurrence of dugongids in the southern WAC. Dioplotherium and Metaxytherium also occur in the early Miocene of northern Brazil. The presence of these taxa as far south as Entre Ríos latitudes suggests two possible dispersal routes: 1) across a marginal connection between a southern arm of the Amazonian Sea and the Paranaense Sea, or; 2) along the Brazilian coast. Lastly, the occurrence of dugongids, which feed mainly on seagrasses, indicates that these marine angiosperms were present in the region as well.