Alligator
From Tardis Wiki, the free Doctor Who reference
The Alligator is a type of crocodilian that can be found in the United States and in China.
During the Dalek Invasion of Earth, many animals escaped from zoos during the plaugue. Most of them died but reptiles such as the alligators thrived in the sewers. An alligator almost ate Susan but was killed by David Campbell. (DW: The Dalek Invasion of Earth)