Palaeontologists from the University of Alberta in Canada have unearthed the world's largest-ever Tyrannosaurus rex.

Key points: The T-rex skeleton is 13 metres long and dates back 66 million years

The T-rex skeleton is 13 metres long and dates back 66 million years The bones were encased by sandstone, which took a decade to remove before scientists could study them more closely

The bones were encased by sandstone, which took a decade to remove before scientists could study them more closely Study lead author Scott Persons said "this particular Tyrannosaurus is the largest terrestrial predator known to science"

Scotty, nicknamed after a celebratory bottle of scotch, has leg bones suggesting a living weight of more than 8,800 kilograms, making it bigger than all other carnivorous dinosaurs.

The study, first published in the Anatomical Record, found the T-rex was 13 metres long and lived about 66 million years ago.

It was first discovered in Saskatchewan near the US border in 1991, but sandstone that had encased the skeleton took over a decade to remove.

Now scientists have been able to study the skeleton more closely.

"This is the rex of rexes," said Scott Persons, lead author of the study and postdoctoral researcher in the Department of Biological Sciences.

"There is considerable size variability among Tyrannosaurus. Some individuals were lankier than others and some were more robust.

"Scotty exemplifies the robust.

"Take careful measurements of its legs, hips, and even shoulder, and Scotty comes out a bit heftier than other T-rex specimens."

The skeleton not only takes the prize for its weight and size, but also its age.

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"Scotty is the oldest T-rex known," Dr Persons said.

"By which I mean, it would have had the most candles on its last birthday cake.

"You can get an idea of how old a dinosaur is by cutting into its bones and studying its growth patterns.

"Scotty is all old growth."

The dinosaur was thought to have been around 30 years old when it died.

Dr Persons also said it had a violent life, with many injuries found through scarred bone.

The battle scars included broken ribs, an infected jaw, and what may be a bite from another T-rex on its tail.

"I think there will always be bigger discoveries to be made," Dr Persons said.

"But as of right now, this particular Tyrannosaurus is the largest terrestrial predator known to science."