Archaeopteryx

Archaeopteryx (PROSE: The Room With No Doors) was a dinosaur with both reptilian features and feathers. It was sometimes regarded as one of Earth's earliest birds (PROSE: Blood Heat) or a link between reptiles and birds. This was believed until true birds were found fossilised in rock strata below archaeopteryx. (PROSE: Placebo Effect)

Archaeopteryx was first identified by Christian Erich Hermann von Meyer when Professor George Challenger was a boy. Challenger described it looking like a turkey and a Komodo dragon. (PROSE: The Found World)

Christine Summerfield saw a fossil of a half-human, half-sphinx creature and it reminded her of the famous archaeopteryx fossil in the British Museum. (PROSE: Dead Romance)

The Child resembled an archaeopteryx without flesh or feathers. (PROSE: Scary Monsters)

Chris Cwej found a fossilised Archaeopteryx in a refrigerator in the Doctor's TARDIS. (PROSE: The Room With No Doors)

On the Silurian Earth in 1993, the Seventh Doctor made cooing noises at an archaeopteryx that landed on his hand. (PROSE: Blood Heat) However, when the Eighth Doctor saw an archaeopteryx in Antarctica in 12,000,000 BC, he believed it was not real like H. P. Lovecraft's fictional Elder Things. (PROSE: The Taking of Planet 5)

According to Ash Juliandis of the 26th century, archaeopteryx was actually a 20th century hoax that was not discovered until the 22nd century. Someone actually put pigeon bones in a slab of putty and claimed it was a dinosaur with feathers. (PROSE: Down)

Behind the scenes
"The Pterodactylus really isn't a bird – but just below him there, you can see a creature that's trying very hard to become one. It's called the Archaeopteryx, a reptile that's actually managed to grow some feathers. Not very many, mind you, but at least it's trying! As yet it really isn't much of a flyer. It's not very big either - about the size of a crow. In fact it'll take quite a few million years to evolve into the birds you know today . .."

- Fourth Doctor

Archaeopteryx is also one of the many dinosaurs featured in NOTVALID: The Doctor Who Dinosaur Book, an activity book featuring the Fourth Doctor.