Oldest record of Leptodactylus Fitzinger, 1826 (Anura, Leptodactylidae) from the Early Pliocene of the South American Pampas

GÓMEZ R. O.; PEREZ BEN C. M.; STEFANINI M. I.; TURAZZINI G. F.

La Rioja

Congreso; XXVII Jornadas Argentinas de Paleontología de Vertebrados; 2013

Asociación Paleontológica Argentina

The Neotropical frog genus Leptodactylus is one of the taxonomically most diverse of all neobatrachian anurans. Despite the genus being highly diversified and widely distributed today, the fossil record is scanty and restricted to the Quaternary of the Neotropics. Herein we report and describe a new record of total group Leptodactylus, consisting of a proximal part of right illium (MLP87-II-25-5) and a nearly complete sacrum (MLP87-II-25-6). The new fossil-frog remains come from the Monte Hermoso Formation exposed at Farola de Monte Hermoso. This unit yielded a rich vertebrate fauna that was recognized as the Neocavia depressidens Biozone, the biostratigraphic basis of the early Pliocene Lower Chapadmalalan Stage. We evaluate both qualitative and quantitative characters and discuss the taxonomic value of body size in the context of living Leptodactylus. A number of features of the fossil elements (morphology of the dorsal protuberance and deep supracetabular fossa of the ilium, high, sharp transverse crest on the neural arch of the sacrum) suggests an affinity with the living species of the L. latrans species group and, particularly, with L. latrans. However, the lack of resolution of Leptodactylus interrelationships and, thus, the lack of osteological synapomorphies of the species groups and species within the genus conspire against the allocation fo the fossils to crown Leptodactylus until they are studied in a rigorous phylogenetic context. In any case, the new material constitutes the oldest record of total group Leptodactylus and extends its stratigraphic range back to the early Pliocene.