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The Teeny Tyrant from Down Under

A pubis bone from a human-sized tyrannosaur has been discovered in Australia—the first time these tyrant reptiles have ever been found in the southern continents.

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Colossal tyrannosauruses, such as Jurassic Park’s anachronistic T. rex, filled the apex predator niche during the Late Cretaceous, around 70 million years ago, but their fossil record for the 100 million years before that has been meagre. Now palaeontologists from the UK and Australia describe a 30-cm-long, distinctively-tyrannosauroid pubis bone found in Victoria’s Dinosaur Cove in Science.

This fossil, NMVP186046, not only shows that tyrannosauruses were not restricted to Laurasia (the northern super-continent), but also that their “characteristic short arms and powerful jaws” were probably around the world by the Early Cretaceous. But while T. rex, was 12 metres long and weighed in at around 4,000 kilograms, this mini-T would have been about three metres long and weighed in at a piffling 80 kg, only slightly heavier than a light heavyweight boxer.

“Some scientists thought tyrannosaurs never made it down south,” says author Roger Benson from University of Cambridge (news release). “Although we only have one bone, it shows that 110 million years ago small tyrannosaurs like ours might have been found worldwide. This find has major significance for our knowledge of how this group of dinosaurs evolved.”

This fossil is from the mid-stages of super-continental break-up, when the southern continents separated from the northern ones, but had not drifted apart from each other.

“It’s these discoveries, mostly man-sized or smaller, that have filled in the story of tyrannosaur evolution,” Benson says (ABC news). But this find leaves him wondering why the northern tyrannosauruses reached ferocious proportions while in the south, the wee tyrannosaur seemed “to just fade into obscurity” (NatGeo).

Image: Roger Benson

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