Silurian pet

The Silurian pet encountered by the Third Doctor, Spencer and Davis at Wenley Moor was, according to some accounts, a Tyrannosaurus rex, (PROSE: Doctor Who and the Cave-Monsters, The Behemoths) although according to another it was "unlike any dinosaur [the Doctor] had seen before". (TV: Doctor Who and the Silurians)

In any case, having been preserved from extinction by the Silurians, it was revived with them in the 20th century, where it guarded the caves underneath Wenley Moor. The pot-holer Davis lost his life to the beast, and Major Baker was attacked and wounded by the creature after he fired upon a Silurian he had seen. (TV: Doctor Who and the Silurians)

Behind the scenes

 * The dinosaur featured in Doctor Who and the Silurians was made by visual effects assistant Anna Baybrooke, and operated by visual effects assistant Bertram A Collacott. The character was listed as "Bertram, the Friendly Monster" on script cast lists, played by "himself". (REF: Who-ology: The Official Miscellany)
 * In the original television story, the Theropod species of this creature was left unclear, however the novelisation stated that it was in fact a T-Rex. However, this is still never made clear in the original episode, and is in fact rather unlikely given that the Doctor claims to not recognise it from the Mesozoic period. The implication is that this is some new species specially engineered by the Silurians themselves. However, the novel alters this, explicitly identifying in multiple places its species as one of the most iconic of real world dinosaurs, and removing the Doctor’s line about unfamiliarity with it.