Tyrannosaur bone in Australia raises questions

LOS ANGELES – Tyrannosaurs may have stalked far more of the globe than previously thought.

Scientists for the first time have found evidence of an ancestor of Tyrannosaurus rex in the Southern Hemisphere, a discovery that could shed light on tyrannosaurs’ evolutionary lineage – which many scientists had thought was restricted to the Northern Hemisphere after the continents began to separate.

Tyrannosaurs had previously been documented only in Asia, Europe and North America, but a hip bone discovered in Australia could only have come from a tyrannosaur, researchers have concluded. They described their finding in a paper published online Thursday in the journal Science. The discovery raises questions about how and why the two-legged carnivores evolved to become dominant predators above the equator, and why they may have failed to do so below it.

“We think tyrannosaurs became global early in history,” said lead author Roger Benson, a paleontologist at the University of Cambridge, “but for some reason, in the north tyrannosaurs became exceptionally successful predators – and in the south, they just dwindled away.”

Benson, along with colleagues at the Natural History Museum in London and Museum Victoria in Melbourne, concluded that tyrannosaurs lived Down Under after analyzing a distinctive bone discovered at Dinosaur Cove in Victoria, Australia.

The bone had been uncovered, along with hundreds of other fossils from a variety of species, by Museum Victoria paleontologist Thomas Rich in 1989. Last year, Rich took them to Benson and other colleagues in Europe to see if they could identify any of the fossils. Among them was the hip bone.

This new dinosaur was much smaller than T. rex – probably about 175 pounds and 9 feet long as opposed to T. rex’s 4 tons and 40 feet. The hip bone itself measures about a foot long.