First record of squamate reptiles from the Oligocene of South America

Abstract

Squamata are known from South America since the Cretaceous, but their fossil record has an occurrence gap between the late Eocene and early Miocene. Fossils recovered from the Sarmiento Formation (Deseadan South American Land Mammal Age, late Oligocene) at Cabeza Blanca (45°S) partially fill this interval. The squamates recovered from Cabeza Blanca include both lizards (an indeterminate Iguanidae and a probable Iguaninae) and snakes (Madtsoiidae). If these taxonomic assignments are correct, the presence of an Iguaninae at such a latitude is unexpected because these lizards are presently absent from Argentine territory. The madtsoiid, here referred to Madtsoia, would extend the Cenozoic record of this genus back to around 16 Ma. The squamate fauna from Cabeza Blanca is compatible with warm and humid environments inferred for the Patagonian Deseadan.

众所周知，有鳞目在南美自白垩纪起就存在了，但他们的化石记录在晚始新世和早中新世之间有一个间断。从卡韦萨布兰卡（45°S）的Sarmiento组采得的化石（渐新世晚期Deseadan南美陆地哺乳动物时代）填补了这一空白。从卡韦萨布兰卡采得的有鳞类包括蜥蜴（不确定Iguanidae和可能的Iguaninae）和蛇（Madtsoiidae）。如果这些分类群的鉴定是正确的，Iguaninae在这样一个纬度的存在是意想不到的，因为这些蜥蜴目前在阿根廷领地缺失。这些madtsoiid，这里被称为Madtsoia，将该属的新生代记录往回推约16Ma。卡韦萨布兰卡的有鳞动物群适应于所推断的巴塔哥尼亚Deseadan温暖潮湿的环境。