A new international study has revealed that giant sharks were swimming in Australian waters much earlier than scientists once thought — by at least 10 million years.
The research, co-authored by Dr Mikael Siversson, Head of Earth and Planetary Sciences at the Western Australian Museum, shows that some extinct sharks reached enormous sizes just 20 million years after their group first appeared.
“This discovery changes the timeline for when sharks started getting really big,” Dr Siversson said.
“It turns out, they evolved a giant body size much earlier than we originally thought and were already top predators in shallow seas.”
The study focused on five fossilised vertebrae discovered at the Darwin Formation in northern Australia. They were identified as belonging to the now-extinct cardabiodontids, a group first described in 1999 by Dr Siversson from fossils found in Western Australia’s Giralia Range.
Using advanced statistical methods and data from nearly 2,000 modern sharks, researchers estimated that these ancient sharks were 6-8 metres long and could have weighed more than 3 tonnes, bigger than white sharks today.
“This is the most detailed analysis ever done on extinct shark size using vertebrae,” Dr Siversson explained.
“We used new techniques and a huge dataset to make sure our estimates were well supported. That’s part of the reason the study was accepted in a high-ranking journal”
Cardabiodontids were the first sharks in their group — known as neoselachians — to evolve a giant body size. Their fossils highlight the exceptional record of Cretaceous sharks in Australia and show that these ancient predators were already shaping marine ecosystems long before the rise of famous giants like Megalodon.
“These sharks were massive, and they lived in shallow coastal waters. That tells us a lot about how ancient food webs worked and it shows just how important Australia’s fossil sites are for understanding prehistoric life.”
This discovery not only rewrites the timeline of shark evolution but also reinforces Australia’s global significance in paleontological research. With each new fossil find, we gain a clearer picture of the ancient oceans and the incredible creatures that once ruled them.
The published paper, titled Early gigantic lamniform marks the onset of mega-body size in modern shark evolution, is available to read here
