Rhedosaurus

Rhedosaurus (name meaning Rhede's lizard, named after the famous movie monster of the same name) is an extinct genus of large lizard that lived in what is now South America during the Late Cretaceous. It largely resembled its namesake in general appearance and was among the largest lizards in prehistory, approaching the Australian Megalania of the Pleistocene in size, growing up to about 20 feet and weighed almost the same as Megalania. The Rhedosaurus was a carnivore and most likely fed on fish, frogs, smaller reptiles, birds, mammals, and carrion. It is unknown why did Rhedosaurus became extinct, but it may have been due to the asteroid/comet impact that smashed the Gulf of Mexico, causing a cloud of ash and acid rain to kill of (most) plant life, killing off the food sources of Rhedosaurus.