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With its sharp teeth and short arms, Tyrannosaurus rex is possibly the most famous of all the dinosaurs.

Now a group of researchers have claimed the predator actually includes three species instead of the single T. rex - a suggestion not all palaeontologists (people who study dinosaurs) agree with.

T. rex, meaning tyrant lizard king, has been the sole species of the genus Tyrannosaurus, recognised since the dinosaur was first described in 1905. A genus is a wider group of related living things compared to a species.

Three researchers, led by independent palaeontologist Gregory Paul, who was a consultant on the Jurassic Park films, have looked about 38 T. rex fossils and made a statement which has shook the palaeontology world!

They think the T. rex should be split into three species, suggesting there should also be T. imperator, meaning "tyrant lizard emperor," and T. regina, meaning "tyrant lizard queen."

The study, published in the journal Evolutionary Biology highlights differences in the thighbones, some are larger and some lighter, and also differences in the number of teeth on the lower jaw.

The researchers even think some famous Tyrannosaurus fossils should be re-named - like the Tyrannosaurus skeleton at the Field Museum in Chicago, which they believe is actually a T. imperator.

But not all palaeontologists agree, including Professor Steve Brusatte from the University of Edinburgh. He wrote on social media: "Regarding T. rex: yes, there is variation in the fossils, but it is minor. Three distinct species can't (yet) be defined based on clear, explicit, consistent differences. It's all still T. rex to me."

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