First record of a neobatrachian frog (Lissamphibia: Neobatrachia) from the Eocene–Oligocene Aiuruoca Basin, Brazil

Abstract

ABSTRACT Despite the widespread diversity of neobatrachian frogs in South America nowadays, their fossils remain notably sparse, particularly during the Palaeogene. Consequently, the discovery of fossils attributed to neobatrachians constitutes a significant contribution to our understanding of their past distribution and diversity. Here, we report a new neobatrachian fossil from the Eocene – Oligocene Aiuruoca Basin in Brazil. The fossil record known from this unit, which is still inadequately documented, includes coprolites, plants, insects, fishes, and also frogs. Prior investigations of these anurans attributed approximately 200 specimens to an as-yet unnamed Pipidae species. The partially preserved specimen described herein (MZSP-PV 1333) clearly differs from the pipid-like fossils by the presence of procoelous vertebral centra, a sacrum separated from the urostyle, bicondylar sacro-urostylar articulation, and fused distal carpals 3 + 4 + 5. However, the absence of additional diagnostic features prevents a confident classification into a more specific subgroup, being thus identified as Neobatrachia indet. The identification of this new frog morphotype suggests that the anuran diversity in the Aiuruoca Basin is more extensive than previously understood, and further emphasises the palaeontological significance of this unit for ongoing research and collection endeavours.