Framed 20 x 16 Print. Tyrannosaurus rex dinosaur, artwork. T. rex was a carnivorous theropod dinosaur that existed in the Upper Mastrichtian stage of the Cretaceous Period, between 65 & 67 million years ago. It was one of the largest known carnivorous dinosaurs, measuring 12.4 metres long & between 4.6 to 6 metres tall. Its skull was around 1.6 metres long & the eye sockets about 10 centimetres wide. Adults may have weighed around 7