Was there a prehistoric alligator that was five times the size of those alive today?

A picture of a large alligator

Deinosuchus is a large alligatoroid from the late-Cretaceous (73-80 million years ago) of the USA. It is in the same superfamily, but not an ancestor, of today’s alligators. Its body length is thought to have been up to 12m (39ft). The remains are incomplete, which makes it hard to accurately measure its length, but it’s possible to compare the bones with those of smaller alligator skeletons to get a rough size. Its maximum weight (not length) was said, in the journal Nature in 1999, to be between three and five times the weight of today’s largest crocodilians. There are several other giant fossil crocodilians and crocodylomorphs; the type specimen of rhamphosuchus is in the NHM.

Dr Lorna Steel, Palaeontology, NHM, London.