The 220-Million-Year-Old Bone That Rewrote Dinosaur Evolution

In 1963, a grazier named Alan Bartholomai reached into the wall of a sheep paddock near the town of Chinchilla, in southeast Queensland, and pulled out a dinosaur ankle bone the size of a clenched fist. He did not know it then, but the bone would sit in a museum drawer for four decades before anyone realised what it meant: that the oldest dinosaur ever found in Australia did not belong to the southern branch of the dinosaur family tree, but to a lineage that palaeontologists thought had evolved millions of years later, in the northern continents.

The Bone in the Drawer

The fossil, catalogued as QMF 18041, came from the Blackstone Formation, a layer of Triassic sediment laid down about 220 million years ago in a broad river valley. For years it was labelled simply as an indeterminate theropod — one of the meat-eating dinosaurs. That classification seemed unremarkable. Australia's Triassic dinosaur record is sparse; most of the continent's dinosaur riches come from the Cretaceous, much later.

In 2007, a team led by palaeontologist Phil Bell revisited the specimen. They cleaned away the remaining matrix, studied the bone's articular surfaces, and compared it with dinosaur ankles from around the world. The anatomy was unmistakable: the bone belonged to a neotheropod, a group of early carnivorous dinosaurs that includes Coelophysis and the ancestors of Tyrannosaurus rex. But neotheropods of this age — the Norian stage of the Late Triassic — were thought to be confined to the northern continents, particularly North America and Europe.

QMF 18041 is a single bone, 12 centimetres long, that challenges a century of biogeographic assumptions.

The southern continents had their own Triassic dinosaurs: the basal sauropodomorphs, the long-necked herbivores like Plateosaurus and its kin. The earliest neotheropods were supposed to have evolved later, after the supercontinent Pangaea had already begun to fragment, and to have spread southward only in the Jurassic. Here was evidence that they had reached Australia at the same time they appeared in the north — or perhaps earlier.

A World Without Barriers

The Blackstone Formation preserves a humid, seasonal floodplain. Pollen and spores from the same layer show a landscape of ferns, cycads, and conifers, with seasonal rainfall and occasional droughts. This was not an isolated island continent. In the Late Triassic, Australia was still joined to Antarctica, South America, Africa, and India as part of Gondwana, which was itself still embedded in the supercontinent Pangaea.

The presence of a neotheropod in Queensland at 220 million years ago suggests that these early carnivorous dinosaurs had a Pangaean distribution from the beginning — not a northern origin followed by a slow southern migration, but a rapid spread across a world without oceans. The bone implies that dinosaur evolution in the Triassic was more connected, more global, than the textbooks had assumed.

It also means that Australia's earliest dinosaurs were not just the long-necked herbivores of the southern stereotype. The predators arrived at the same time, chasing them across the same floodplains.

What One Bone Can Say

A single ankle bone cannot tell us the animal's full body size — estimates range from two to five metres — nor its exact species. But it can answer questions of time and place. QMF 18041 extends the known range of neotheropods in Gondwana back by roughly 15 million years. It is a data point that forces a redrawing of the map.

Since the Chinchilla discovery, other Triassic dinosaur fossils have emerged from Queensland and New South Wales — a femur here, a tooth there — each filling in the picture. The picture that emerges is of a Triassic dinosaur fauna far more diverse and widespread than anyone guessed in 1963. The ankle bone from a sheep paddock was not an anomaly. It was a sign that the southern continents were not dinosaur backwaters. They were part of the story from the very first chapter.