Rauisuchidae

Rauisuchidae is a group of large (up to 6 metres (20 ft)) predatory Triassic archosaurs. Some disagreement exists over which genera should be included in the Rauisuchidae and which should be in the related Prestosuchidae and Poposauridae, and indeed whether these should even be thought of as separate valid families. Rauisuchidae in the modern sense was defined by Sterling Nesbitt in 2011 as the most inclusive clade containing Rauisuchus tiradentes, but not Prestosuchus chiniquensis, Poposaurus gracilis, or Crocodylus niloticus (the Nile crocodile). In this modern sense, rauisuchids are recovered as members of the clade Loricata, being the sister taxon of Crocodylomorpha (the group including living crocodilians), and being more derived than taxa such as Prestosuchus and Batrachotomus. Rauisuchids occurred throughout much of the Triassic, and may have first occurred in the Early Triassic if some archosaurian taxa such as Scythosuchus and Tsylmosuchus are considered to be within the family. An early cladistic analysis of crocodylotarsan (pseudosuchian) archosaurs included Lotosaurus, Fasolasuchus, Rauisuchus, and "the Kupferzell rauisuchid" (later called Batrachotomus) within the Rauisuchidae. However, a later study found that Batrachotomus was a more basal pseudosuchian only slightly more "advanced" than Prestosuchus. In addition, the toothless Lotosaurus has been found to be more closely related to the Ctenosauriscidae, a clade of poposauroids with sails on their backs. Two genera, previously classified as poposaurids, are in fact rauisuchids. These include Teratosaurus and Postosuchus.