New Squamata and Aves from the Collón Curá Formation at Cerro Zeballos (middle-late Miocene), Chubut province (Argentina)

Abstract

Sustained fieldwork at the fossil locality Cerro Zeballos, Collón Curá Formation (middle-late Miocene) in northwestern Chubut province, has produced abundant fossil vertebrates (fishes, anurans, tortoises, marsupials, rodents, xenarthrans, and notoungulates). Here we present new findings of squamate and avian remains. Squamates are represented by several lizards and one snake. The fossils assigned to lizards consist in tooth-bearing bones (maxillae and dentaries), most of which are assigned to Tupinambinae Teiidae based on the extended anterior aperture of Meckel ́s canal and/or of subpleurodont tooth implantation (LIEB PV 5172, 5293, 5301, 5302, 5310 5312, 5314, 7669). Some of these fossils assigned to Tupinambinae preserve weakly bicuspid posterior teeth, which indicate affinities with Callopistes, allowing the resolution of previous uncertainties regarding Tupinambinae record of Collón Curá Formation. Two other lizard specimens are interesting, LIEB PV 5294 presents a rare tooth morphology, with an evident bicuspid condition where the mesial cusp is dominant, indicating probably a new Tupinambinae taxon. LIEB PV 5313 is a delicate, sub-rectangular (i.e., not cuneiform) dentary, with a closed, fused Meckel's canal, no anterolateral process of the coronoid, pleurodont teeth with parallel tooth outlines, corresponding to a Pleurodonta lizard. Finally, among the squamate fossils, a partially articulated series of precloacal vertebrae (LIEP PV 5311) are preliminary assigned to an indeterminate snake. Bird fossil consists on two isolated remains: 1) LIEB PV 5299 is a fragment of a right trochlea metatarsi III assigned to a medium-sized Phorusrhacidae based on the presence of a canal present between trochlea metatarsorum III and IV, and a scar at the end of the dorsal margin of the trochlea III; and 2) LIEB PV 5300 is a right shaft of tarsometatarsus of a Falconidae related to Falco based on the presence of a marked furrow proximally to the small foramen vasculare distale, a sharp lateral edge, and by a marked furrow that runs from the facies subcutanea medialis to the facies dorsalis. Therefore, the new specimens of at least two tupinambine teiids (cf. Callopistes and a new taxon), a pleurodont lizard, a snake, a falconid, and a terror bird, increase significantly the vertebrate diversity of the Cerro Zeballos fossil locality.