First southern tyrannosaur uncovered

26 March 2010

Evidence for the first ever tyrannosaur dinosaur in the southern continents has been uncovered and is reported in the journal Science today.

Scientists from the Natural History Museum, University of Cambridge, and the Museum Victoria, Australia, identified a fossilised hip bone as belonging to an ancestor of T.rex. It lived 110 million years ago, earlier in the Cretaceous than its giant relative, and gives clues about the early evolution of this group of dinosaurs.

Hip bone of tyrannosaur
Part of the 110-million-year-old fossilised hip bone of an ancestor of T.rex uncovered in Australia

Part of the 110-million-year-old fossilised hip bone of an ancestor of T.rex uncovered in Australia © Dr Roger Benson, University of Cambridge

The 30cm-long hip bone was uncovered at Dinosaur Cove in Victoria, Australia and is the first tyrannosaur found in any southern continent. 'The bone is unambiguously identifiable as a tyrannosaur because these dinosaurs have very distinctive hip bones,' says Dr Roger Benson of the University of Cambridge, part of the research team.

Smaller than T.rex

The tyrannosaur, currently known as NMV P186069, was much smaller than the mighty Tyrannosaurus rex, at about 3m long and weighing around 80kg and lived 40 million years earlier. The giant size of T.rex evolved later on in the groups' evolution.

Southern continents

Until now, there had been an absence of fossil evidence of tyrannosaurs in the southern continents and this led scientists to question whether these dinosaurs ever reached this part of the world. This new research shows they did.

Dr Paul Barrett, fossil expert at the Natural History Museum and member of the research team comments. 'The absence of tyrannosauroids from the southern continents was becoming more and more anomalous as representatives of other 'northern' dinosaur groups started to show up in the south.

'This find shows that tyrannosauroids were able to reach these areas early in their evolutionary history and also hints at the possibility that others remain to be discovered in Africa, South America and India.'

Supercontinent

During the time of the dinosaurs the continents gradually went from a single supercontinent towards something like their present-day arrangement.

This tyrannosaur is from the mid-stages of this continental break-up (shown in the top image), when the southern continents of South America, Antarctica, Africa and Australia had separated from the northern continents, but had not separated from each other.

Giant T.rex in the north

But what about the giant T.rex? Did it ever make it to these southern parts? And why did it evolve into the giant predator only in the northern hemisphere?

'It is difficult to explain why different groups succeeded in the north and the south if they originally existed in both places,' explains Dr Benson.

'What we need to know now is just how diverse the early radiation of tyrannosaurs was, why they went extinct, leaving only giant-sized, short-armed species like T. rex, and how successful they might have been in the southern hemisphere. We can only answer these questions with new discoveries.'

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