Purussaurus is an extinct genus of giant caiman that lived in South America during the Miocene epoch, 8 million years ago. It is known from skull material found in the Brazilian, Colombian and PeruvianAmazonia, and northern Venezuela. The estimated skull length for one large individual of the type speciesP. brasiliensis is 1,400 millimetres (55 in).Paleontologists estimate that P. brasiliensis may have measured around 11 to 13 metres (36 to 43 ft) in length, which means that Purussaurus is one of the largest known crocodilians ever to have existed. Two other extinct crocodilians, Sarcosuchus and Deinosuchus, have similar proportions, but both are geologically much older, dating from the Early and Late Cretaceous, respectively, and another from the Miocene of India, Rhamphosuchus, is estimated to be slightly smaller, though assumed to have been proportioned like a gharial. During the summer of 2005, a Franco-Peruvian expedition (the Fitzcarrald expedition) found new fossils of Purussaurus in the Peruvian Amazon (600 km from Lima).
Analysis of a biomechanical model of the skull of Purussaurus has indicated that it would have been capable of performing the "death roll" maneuver used by extant crocodilians to subdue and dismember their prey.
Scale diagram showing the size of P. brasiliensis (red)
Brazilian P. brasiliensis is associated with sharks, rays, freshwater teleosts, lungfish, turtles including Stupendemys, crocodilians including Charactosuchus, Gryposuchus, and Mourasuchus, Anhinga birds, and mammals including sloths, bats, rodents, the primate Stirtonia, and river dolphins. River, floodplain, and lake environments were present. Marine and freshwater fish, turtles, crocodilians, and terrestrial and aquatic mammals are associated with Venezuelan P. mirandai. Its environment is described as tropical and coastal. The earlier Colombian P. neivensis lived alongside a massive variety of fauna, including astrapotheres like Granastrapotherium and Xenastrapotherium, the early species of Mourasuchus and Gryposuchus, and the terrestrial crocodyliform Langstonia. This fauna dates from 13 million years ago, in the Laventan stage of the Late Miocene. 
^ abAguilera, O. A., Riff, D., and Bocquentin-Villanueva, J. (2006). "A new giant Purussaurus (Crocodyliformes, Alligatoridae) from the Upper Miocene Urumaco Formation, Venezuela." Journal of Systematic Palaeontology4(3): 221–232.
^Blanco, R. E.; Jones, W. W.; Villamil, J. N. (2014-04-16). "The 'death roll' of giant fossil crocodyliforms (Crocodylomorpha: Neosuchia): Allometric and skull strength analysis". Historical Biology: 1. doi:10.1080/08912963.2014.893300.edit
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Langston, W. 1965. "Fossil crocodilians from Colombia and the Cenozoic history of the Crocodilia in South America". University of California Publications in Geological Sciences 52:1-169.