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An older, southern Tyrannosaur

Fossil remains of a dinosaur related to Tyrannosaurus rex. This image shows part of the hip, which was discovered in Australian rocks and is approximately 110 million years old.
[Image © Dr. Roger Benson, Cambridge]

Large tyrannosaurs, such as T. rex, were the top predators during the Late Cretaceous period, about 100 million to 65 million years ago—but their history is not well documented for the 100 million years before that, and until now, their bones had only been found in the northern hemisphere. This gap in the fossil record has led researchers to wonder if tyrannosaur-like dinosaurs ever existed in the southern hemisphere, and how the huge dinosaurs emerged as such fierce predators anyway.

The first relative of Tyrannosaurus rex from the southern continents has been discovered in Dinosaur Cove, Australia. This map shows the location of Dinosaur Cove approximately 110 million years ago.
[Image © Dr. Roger Benson, Cambridge]

Now, the discovery of a small tyrannosaur fossil in Australia is changing what scientists know about tyrannosaurs' reign on Earth. Roger Benson and colleagues have found a pubic bone from the Early Cretaceous period—about 146 million to 100 million years ago—in Victoria, Australia, that belonged to a much smaller reptile with a tyrannosaurid-like body plan. This new fossil has all of the characteristics of T. rex, including the short arms and powerful jaws, but they are attached to a much smaller body.

The fossil find proves that these fierce predators did, in fact, live in the southern hemisphere long before their more massive ancestors ruled the Late Cretaceous northern hemisphere. The researchers also suggest that these smaller tyrannosaurs might have spread across the world, occupying both hemispheres for a time.

They categorize the prehistoric creature, known as NMV P186046, as a tyrannosaur, but imagine that it shared some physical traits with Raptorex as well. This research appears in the 26 March 2010 issue of Science.