First continental vertebrates from the marine Paraná Formation (Late Miocene, Mesopotamia, Argentina): Chronology, biogeography, and paleoenvironments

Abstract

First records of continental vertebrates from the upper levels of the Paraná Formation (Late Miocene) at La Juanita locality, Entre Ríos Province (Mesopotamia, Argentina), are reported and evaluated from chronological, paleobiogeographical, and paleoenvironmental perspectives. Among caviomorph rodents, caviids, hydrochoerids, and the extinct octodontoid Plesiacarechimys are described. The pampatheriid Scirrotherium sp. and a phoenicoptherid bird are identified. A “pre-Huayquerian” age (older than 8.7 Ma) is proposed for the fossil bearing levels. The “Paranense Sea”, one of the most widespread Middle-Late Miocene Atlantic transgressions that covered southern South America, is interpreted as an important geographical barrier promoting vicariance of the Plesiacarechimys lineage. Cavioids recovered from the Paraná Formation represent the first stages of the radiation of these rodents at the latitude of Entre Ríos Province in the context of the whole South American subcontinent. The genesis of the fossiliferous level corresponds to a storm deposit in a littoral marine environment. Capybaras and flamingos suggest the presence of water bodies, saline lagoons, mudflats, or shallow brackish coastal or inland lakes, in accordance with the geological data of the Paraná Formation.