Alligator

Alligators were a type of crocodilian that could be found in the United States and in China.

Nero threatened the Doctor, stating he would build a moat around him and fill it with alligators. However he withdrew from this action when the Doctor inspired him to burn Rome. The Doctor then told his captives the punishment would be reserved for them if he and Vicki were not freed. (DW: The Romans)

During the 22nd century Dalek invasion of the solar system, including Earth, many animals escaped from zoos during the plague. 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)