A reptile was a type of cold-blooded animal.
On Earth[]
During the 2150s Dalek invasion of Earth, many animals escaped from zoos during the plague. Most of them died, but reptiles such as alligators thrived in the London sewers. (TV: The Dalek Invasion of Earth)
Dodo Chaplet pointed out a chameleon to Steven Taylor while they were aboard the Ark. (TV: The Ark)
One of the terms that Silurians referred to themselves as was "Earth Reptile". (PROSE: The Scales of Injustice) By the time of the Earth Empire this term had expanded to include the Sea Devils. (PROSE: Love and War) Both of these species were classified as homo reptilia. (COMIC: Clara Oswald and the School of Death) "Reptile" could also be used as an insult against the species. (TV: The Name of the Doctor)
Elsewhere[]
The Cynrog were reptilian humanoids who hid behind masks and worshipped the chaos god Balor. (PROSE: The Nightmare of Black Island)
The Re'nar were intelligent lizard-like reptiles from the Matrua Nebula that were at war with the Ju'wes. (COMIC: Ripper's Curse)
Historians who studied the Dalek race believed that, like on Earth, the dominant lifeform on prehistoric Skaro had been large reptilian creatures. (PROSE: Dalek: The Astounding Untold History of the Greatest Enemies of the Universe)
The native species of the planet Destination, the Dalmari, were a reptilian species. (AUDIO: The Destination Wars)