A new species of tyrannosaur dating back almost 80 million years has been discovered by a farmer and his wife in Canada.

Thanatotheristes degrootorum stalked what is now North America more than 79 million years ago, during the late Cretaceous Period, making it the region’s oldest-known tyrannosaur.

The first part of the apex predator’s name, Thanatotheristes, means “reaper of death”, while the second part, degrootorum, honours John and Sandra De Groot, the couple who made the fossil discovery.

Researchers said the new find gave them more insights into the evolution of tyrannosaurs — a group of large predatory dinosaurs that includes the famous Tyrannosaurus rex.

“There are many anatomical features of the skull that differentiates Thanatotheristes,” François Therrien, curator of dinosaur palaeoecology at the Royal Tyrrell Museum in Alberta.

Standing roughly 2.4 metres high with teeth longer than 70 millimetres, the carnivorous dinosaur had many features resembling its younger cousin Tyrannosaurus rex.

But Dr Therrien said no other species of tyrannosaur had ridges along its jaw, and the scales that covered them were likely to be colourful, giving it a very distinctive appearance.

‘We knew it was special’

The De Groots found the fossils, including jaw bones and skull fragments, in 2008 as they hiked along a riverbank in Alberta.

“The jawbone was an absolutely stunning find,” Mr De Groot said.

The remains were determined to be from a tyrannosaur, but the bones that were collected were not believed to contain enough features to clearly differentiate which type.

It wasn’t until University of Calgary masters student Jared Voris took a closer look in 2018 that the distinguishing features were identified.

Mr Voris returned to the site of the discovery with Dr Therrien and the two worked alongside others to analyse the fossils before officially announcing the discovery on Monday.

“I think what’s interesting here is that this discovery was not made by professional palaeontologists but by members of the public,” Dr Therrien said.

Alberta’s rugged and bare landscape has made it one of the top five places in the world for dinosaur fossils.

Dr Therrien said that from his office at the museum he could walk out across the Badlands and discover fossils.

“From some areas of the province you can collect up to six, maybe more, skeletons of dinosaurs every summer,” he told the ABC.

Of the 15 different species of tyrannosaurs, five of them have been found in Alberta.

But most date from between 77 and 66 million years old, making this particular find even more significant.

The last tyrannosaur discovered in Canada was Daspletosaurus, in 1970.