About 120 million years ago, Victoria, Australia, was a land of endless winter. The southern coast was a frigid river valley, its banks lined with pine trees and its waters teeming with fish. Dinosaurs roamed this icy world, but the full picture has long been incomplete. Now, a new discovery is reshaping the history of Australia’s Cretaceous predators — and turning our understanding of dinosaur ecosystems upside down.

Researchers unveiled fossils of the world’s oldest known megaraptorid and the first evidence of carcharodontosaurs in Australia. These findings, led by Ph.D. student Jake Kotevski of Museums Victoria Research Institute and Monash University, reveal a predator hierarchy unlike anything seen elsewhere in the world.

“The discovery of carcharodontosaurs in Australia is groundbreaking,” says Kotevski. “It’s fascinating to see how Victoria’s predator hierarchy diverged from South America, where carcharodontosaurs reached Tyrannosaurus rex-like sizes up to 13 meters, towering over megaraptorids. Here, the roles were reversed.”

Flipping the script

For decades, paleontologists puzzled over Victoria’s fossil records. Fossils of prey animals — like fish and small dinosaurs — abounded, yet no super-predator emerged to claim the top spot. “We are missing a Tyrannosaurus rex,” researchers often mused.

Now, the gap has finally narrowed. Five theropod bones, dug from the upper Strzelecki Group and Eumeralla Formation, point to large, powerful megaraptorids — measuring 6 to 7 meters long. Alongside them were smaller carcharodontosaurs, just 2 to 4 meters long, and agile, meter-long unenlagiines, or “southern raptors.”

But everything was upside down in Australia during this period, it seems. The carcharodontosaurs should’ve been much larger than the megaraptorids.

Australia’s dinosaurs didn’t follow the northern playbook. North America gave us Tyrannosaurus and Triceratops, tales of brute force and sprawling plains. But the southern hemisphere brewed its own recipe.

“It shows in Australia something unique, different to anywhere else in the world, may have happened,” Tim Ziegler, vertebrate paleontology collection manager at Museums Victoria Research Institute, told The Sydney Morning Herald. “We overturn the ecology.”

So what drove this evolutionary reversal? One possibility is that megaraptorids evolved first and grew large, outcompeting carcharodontosaurs. Another is that Victoria lacked the large plant-eating dinosaurs that carcharodontosaurs typically preyed on. Or perhaps the fossils represent juvenile carcharodontosaurs, leaving the mystery of their true size unresolved.

A Land of Cold and Claws

The discovery is the result of decades of work — and a bit of serendipity. Three of the fossils were uncovered between 2022 and 2023 by Museums Victoria volunteer Melissa Lowery, who regularly scours the beaches of Inverloch for traces of ancient life. “I could swear she can smell the stuff,” says Dr. Thomas Rich, senior curator of vertebrate paleontology at Museums Victoria and a co-author of the study.

Other fossils had been hiding in plain sight. One bone, found by Rich’s wife, Pat, in 1987, sat unidentified in a museum drawer for decades. It wasn’t until Kotevski, a self-described dinosaur enthusiast with a T. rex tattoo, began his Ph.D. that the pieces fell into place. After months of comparing the fossils to known dinosaur specimens, he matched them to a carcharodontosaur found in Thailand. “It looked effectively like a mirror of mine,” he says. “My heart skipped a beat.”

This discovery is part of a broader “blossoming of dinosaur research” in the Southern Hemisphere, says Ziegler. For decades, our understanding of dinosaurs was shaped by North American discoveries, where near-complete skeletons of Tyrannosaurus rex and other iconic species were unearthed. Australia, by contrast, was seen as a dinosaur backwater. “What we had were survivors, relics,” Ziegler explains. “But now, we’re seeing a unique dinosaur ecology emerge.”

As Kotevski and his team continue to survey key fossil sites, the mystery of Australia’s Cretaceous predators deepens. “We just need to find more,” he says. “I think the mystery goes on.”

The findings appeared in the Journal of Vertebrate Paleontology.