Fossils discovered in Australia rewrite dinosaur history

Fossils newly unearthed in southeastern Australia have upended long-held assumptions about dinosaur evolution, revealing the world’s oldest known megaraptorid and the first confirmed evidence of carcharodontosaurs on the continent. 

These discoveries paint a vivid picture of an unusual predator hierarchy that once roamed the region during the Early Cretaceous, adding a crucial piece to the puzzle of dinosaur history.

The research was carried out by a team led by Museums Victoria Research Institute and Monash University PhD student Jake Kotevski. 

The study focused on five theropod fossils found along Victoria’s coastline. They were collected in the upper Strzelecki (Bass Coast, dating back roughly 121.4–118 million years) and the Eumeralla Formation (Otway Coast, about 113–108 million years old).

Dinosaurs thriving in Australia 

The newly studied remains suggest an unexpected arrangement of carnivorous dinosaurs. They indicate that large megaraptorids – measuring between six and seven meters long – coexisted alongside smaller carcharodontosaurs that reached only two to four meters in length, as well as the agile, meter-long unenlagiines (nicknamed “southern raptors”). 

This stands in stark contrast to better-known ecosystems where carcharodontosaurs typically surpassed other predatory dinosaurs in size.

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

Two of the newly identified fossils rank among the earliest megaraptorids known worldwide, prompting experts to reconsider their evolutionary timeline. 

Because these megaraptorids thrived in Australia at such an early date, they may have played a more pivotal role in Gondwanan predator communities than previously recognized.

New clues about dinosaur migration 

According to Dr. Thomas Rich, senior curator of vertebrate palaeontology at Museums Victoria Research Institute, the fossils also hint at broader patterns of dinosaur dispersal in the Southern Hemisphere. 

He noted that the findings not only expand Australia’s theropod fossil record but offer compelling evidence of faunal interchange between Australia and South America through Antarctica during the Early Cretaceous. 

“The findings also challenge previous assumptions about body-size hierarchies in Gondwanan predator ecosystems highlighting Victoria’s unique Cretaceous fauna,” xplained Dr. Rich.

These links to other Gondwanan regions bolster the theory that dinosaurs and other animals migrated between connected landmasses before shifting continents isolated certain populations. 

Over time, such isolation could have led to distinct paths of evolutionary development, explaining why Australian megaraptorids, rather than carcharodontosaurs, occupied the apex predator niche.

Significance of museum collections

Beyond revealing hidden chapters of Australia’s dinosaur history, the study demonstrates the significance of museum collections in fueling new scientific breakthroughs. 

Researchers often depend on carefully preserved fossils that can remain unclassified for decades, awaiting fresh analytical methods or new comparative specimens before their true importance is revealed.

“Museum collections are crucial to advancing our understanding of prehistoric life,” said Tim Ziegler, the vertebrate palaeontology collection manager at Museums Victoria Research Institute. 

“Specimens preserved in the State Collection for decades – unidentifiable until now – are providing new insights into the evolution of dinosaur ecosystems.”

The project also illustrates a longstanding tradition of mentorship, continuity, and collaboration among palaeontologists. Senior curator Dr. Rich, at Museums Victoria since 1974, has worked with multiple generations of researchers. 

These efforts culminate in cutting-edge studies like Kotevski’s PhD research, forming a chain of inquiry that steadily advances what we know about ancient life.

Volunteers in the field

Three of the fossils in this study were first identified between 2022 and 2023 by a Museums Victoria volunteer, Melissa Lowery, demonstrating the critical role that community members play in paleontology. 

With an eye for intriguing shapes and textures, volunteers often detect clues that lead to major discoveries.

Kotevski and his colleagues continue to search for additional remains at key sites, including the location where the large megaraptorid was found. 

These expeditions form part of the long-running Dinosaur Dreaming project, responsible for uncovering over 10,000 fossils – from dinosaurs and birds to mammals and marine reptiles – since it began. 

Each new bone or tooth refines scientists’ understanding of the richly varied ecosystems that existed on Australia’s ancient coastlines.

Dinosaurs of Cretaceous Australia

Unusual for reversing the roles typically observed in other continents, Victoria’s predator lineage helps paleontologists envision a world where megaraptorids reigned supreme while smaller carcharodontosaurs prowled in their shadow. 

By confirming that early megaraptorids inhabited the region and that carcharodontosaurs were present yet less dominant, these fossils challenge orthodox views on predator size hierarchies and evolutionary pathways within Gondwana.

As fieldwork continues, each new fragment of bone has the potential to reshape our perspective on how dinosaurs spread across the prehistoric southern supercontinent, adapted to different environments, and carved out ecological niches. 

Together, the fossils detail a singular evolutionary story that sets Cretaceous Australia apart, forever changing how we see the era’s predatory power dynamics – and offering fresh directions for future discoveries.

Image Credit: Artwork by Jonathan Metzger. Source: Museums Victoria

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