Amphibians and squamate reptiles from the Santa Cruz Formation (late Early Miocene), Santa Cruz Province, Argentina: paleoenvironmental and paleobiological considerations

Abstract

The herpetological diversity recorded in the Santa Cruz Formation (late Early Miocene) is low when compared to that of birds and mammals. It includes the anuran Calyptocephalella, an indeterminate "leptodactylid", indeterminate pleurodont iguanians (including those previously assigned to the extinct genus "Erichosaurus"), the tupinambine teiid Tupinambis, and indeterminate "colubrids". The presence of Calyptocephalella in the Estancia La Costa locality represents its southernmost record and might indicate the occurrence of permanent lowland lakes, ponds, and quiet streams, possibly developed in a forested area. The presence of Tupinambis and "colubrids" at around 50° S represents the southernmost record in their respective evolutionary histories, suggesting warmer and probably more humid conditions in the late Early Miocene than those prevailing in southern Patagonia at present. Based upon the diets of extant Calyptocephalella and "colubrids" we consider the Santacrucian Miocene representatives to be small carnivorous vertebrates. Santacrucian pleurodont iguanians should be included in the insectivorous and/or herbivorous groups, whereas Tupinambis would have been a generalist, omnivorous reptile.