Tewkensuchus

Tewkensuchus ("forehead crocodile") is an extinct genus of large-bodied sebecoid notosuchian from the Paleocene of Argentina. The genus was described on the basis of fragmentary skull remains alongside a few vertebrae and finger bones collected from the Salamanca Formation. Though likely a terrestrial predator akin to genera like Sebecus, Tewkensuchus much more closely resembles European forms such as Iberosuchus, Bergisuchus and Dentaneosuchus. These European genera form a clade with Tewkensuchus, which appears to be the sister group to the Sebecidae of South America, with both groups being placed in the clade Sebecoidea. Gonzalo Gabriel Bravo and colleagues furthermore note the great size of the animal, which based on its estimated skull length may have weighed around 300 kg (660 lb), not only making it larger than the largest definitive sebecosuchians of the Cretaceous but also putting it far above the maximum weight generally assumed for terrestrial species that survive the Cretaceous–Paleogene extinction event. Possible explanations for this unusually large size might be that the ancestors of Tewkensuchus and other sebecoids could have been more semi-aquatic than their descendents or that they were terrestrial and simply grew rapidly following the extinction of the dinosaurs.