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The tyrannosaur is known as one of the most fearsome dinosaurs to have ever walked the earth. But new evidence suggests it may have started life the size of a dog.

Researchers have discovered that baby tyrannosaurs - cousin of the fearsome T-Rex - were the size of a Border Collie dog when they were born.

A team of dino experts, known as palaeontologists, from Edinburgh University examined fossilised remains of a tiny jaw bone and claw found in Canada and the US.

The fossils show that the creatures, which lived more than 70 million years ago, were only about 3ft (91cm) long when they hatched from eggs, despite being able to grow to 40ft (12.2m) in length, and weighing about eight tonnes.

That means they start out about the height of a kitchen counter and end up the size of a three-storey building!

The team has also estimated that tyrannosaur eggs - remains of which have never been found - were slightly taller than a PS5 games console (that's around 40cms or 17 inches for people who don't have a PS5 to compare a dinosaur egg to!)

Dr Greg Funston, of the university's School of GeoSciences, said: "These bones are the first window into the early lives of tyrannosaurs and they teach us about the size and appearance of baby tyrannosaurs."

Even though they had a much smaller start to life, Dr Funston explained that the young tyrannosaurs are still pretty big for a baby.

"We now know that they would have been the largest hatchlings to ever emerge from eggs and they would have looked remarkably like their parents," he said adding that the size of the eggs and the similarity to their parents were "both good signs for finding more material in the future".

Tyrannosaurs lived 68 to 66 million years ago in an area which today is north America and are believed to have been wiped out when a huge asteroid smashed into the earth.