Tyrannosaurus rex

Tyrannosaurus rex, also known as Tyrannosaurus or simply T-Rex was a species of Dinosaur that inhabited Equestria millions of years ago.

History
When Princess Celestia and Starswirl the Bearded were traveling through dimensions, among the first universe they came across was a prehistoric realm where they encountered the Tyrannosaurus version of Fluttershy.

When Discord took Fluttershy and the Cutie Mark Crusader on a time-traveling adventure, they eventually came across the dinosaurs. Among the dinosaurs they found was a timid Tyrannosaurus.

During her first Nightmare Night in Equestria, Ocellus found herself in the Castle of Two Sisters as it was burning to the ground. In order to save the animals who were indanger, she transformed into a Tyrannosaurus to scare them all away.