The herpetological diversity recorded in the Santa Cruz Formation (late EarlyMiocene) is low when compared with that of birds and mammals. It includes thecalyptocephalellid anuran Calyptocephalella,an indeterminate “leptodactylid,” indeterminate pleurodontiguanians (including those previously assigned to the extinct genus“Erichosaurus”), thetupinambine teiid Tupinambis, andindeterminate “colubrids.” The presence of Calyptocephalella in the Estancia La Costa locality representsits southernmost record and might indicate the occurrence of permanent lowlandlakes, ponds, and quiet streams, possibly developed in a forested area. Thepresence of Tupinambis and“colubrids” at around 50° S represents the southernmostrecord in their respective evolutionary histories, suggesting warmer andprobably more humid conditions in the late Early Miocene than those prevailingin southern Patagonia at present. Based upon the diets of extant Calyptocephalella and “colubrids” weconsider the Santacrucian Miocene representatives to be small carnivorousvertebrates. Santacrucian pleurodont iguanians should be included in theinsectivorous and/or herbivorous groups, whereas Tupinambis would have been a generalist omnivorous reptile.