the upper part of the Gorro Frigio Formation, which was considered to be approximately 100 million years old (Albian or Cenomanian stage). Later, they were realized to pertain to the much younger La Colonia Formation, dating to the Campanian and Maastrichtian stages (83.6 to 66 million years ago). Novas, in a 2009 book, gave a narrower time span of 72 to 69.9 million years ago (lower Maastrichtian stage). Carnotaurus therefore was the latest South American abelisaurid known. By the Late Cretaceous, South America was already isolated from both Africa and North America. The La Colonia Formation is exposed over the southern slope of the North Patagonian Massif. Most vertebrate fossils, including Carnotaurus, come from the formation's middle section (called the middle facies association). This part likely represents the deposits of an environment of estuaries, tidal flats or coastal plains. The climate would have been seasonal with both dry and humid periods. The most common vertebrates collected include ceratodontid lungfish, turtles, crocodiles, plesiosaurs, dinosaurs, lizards, snakes and mammals. Some of the snakes that have been found belong to the families Boidae and Madtsoidae, such as Alamitophis argentinus. Turtles are represented by at least five taxa, four from Chelidae (Pleurodira) and one from Meiolaniidae (Cryptodira). Among the marine reptiles is the plesiosaur Sulcusuchus erraini of the family Polycotylidae. Mammals are represented by Reigitherium bunodontum, which was considered the first record of a South American docodont, and Argentodites coloniensis, possibly of Multituberculata. In 2011, the discovery of a new enantiornithine bird from the La Colonia Formation was announced. See also Timeline of ceratosaur research Notes References External links The bite of Carnotaurus at Universidad Nacional de Mar del Plata. Skeletal reconstruction by Scott Hartman Brachyrostrans Campanian life Late Cretaceous dinosaurs of South America Cretaceous Argentina Fossils of Argentina Cañadón Asfalto Basin Fossil taxa described in 1985 Taxa named by José Bonaparte