A newly discovered species of dinosaur could hold the evolutionary key to why T. rex became so huge and dominant.

The new Tyrannosaur, named Timurlengia, is 90 million years old. It comes from a point in the fossil record just before Tyrannosaurs started to evolve their great size.

Discovered by US and Russia-based scientists working in Uzbekistan, and studied at the University of Edinburgh, the creature's skull appears to hold some of the secrets to Tyrannosaurs' success.

Dr Stephen Brusatte from the University of Edinburgh showed the fossil to BBC Science reporter Victoria Gill.

Illustration and diagram courtesy of Todd Marshall and T-rex animated footage courtesy of Walking With Dinosaurs