During the dinosaur era, long before creatures like whales, great white sharks, or the colossal megalodon roamed the seas, a formidable shark dominated the waters near what is now northern Australia. This was a time teeming with marine giants of the Cretaceous period.

Scientists examining massive vertebrae unearthed on a beach near Darwin have identified this creature as the earliest known mega-predator of the modern shark lineage. Remarkably, it existed 15 million years prior to any previously discovered giant sharks.

This ancient predator was enormous, measuring approximately 26 feet in length—outstripping the size of today’s 20-foot great white sharks. These findings were detailed in a study published in the journal Communications Biology.

“Cardabiodontids were colossal, predatory sharks prevalent during the later Cretaceous, postdating 100 million years ago,” explained Benjamin Kear, the senior curator of paleobiology at the Swedish Museum of Natural History and a co-author of the study. “This discovery significantly extends the timeline for when we can expect to find these gigantic cardabiodontids.”

Rediscovered fossils pointed to a huge shark

While sharks boast a 400-million-year lineage, the lamniform group, from which modern great white sharks descend, appears in the fossil record dating back to 135 million years ago.

At that time they were small — probably only a meter in length — which made the discovery that lamniforms had already become gigantic by 115 million years ago an unexpected one for researchers.

The vertebrae were found on coastline near Darwin in Australia’s far north, once mud from the floor of an ancient ocean that stretched from Gondwana — now Australia — to Laurasia, which is now Europe.

It’s a region rich in fossil evidence of prehistoric marine life, with long-necked plesiosaurs and ichthyosaurs among the creatures discovered so far.

The five vertebrae that launched the quest to estimate the size of their mega-shark owners were not a recent discovery, but an older one that had been somewhat overlooked, Kear said.

Unearthed in the late 1980s and 1990s, the fossils measured 4.7 inches across and had been stored in a museum for years.

When studying ancient sharks, vertebrae are prizes for paleontologists. Shark skeletons are made of cartilage, not bone, and their fossil record is mostly made up of teeth, which sharks shed throughout their lives.

“The importance of vertebrae is they give us hints about size,” Kear said. “If you’re trying to scale it from teeth, it’s difficult. Are the teeth big and the bodies small? Are they big teeth with big bodies?”

Ancient shark size still holds mystery

Scientists have used mathematical formulas to estimate the size of extinct sharks like megalodon, a massive predator that came later and may have reached 56 feet in length, Kear said.

But the rarity of vertebrae mean questions of ancient shark size are difficult to answer, he added.

The international research team spent years testing different ways to estimate the size of the Darwin cardabiodontids, using fisheries data, CT scans and mathematical models, Kear said.

Eventually, they arrived at a likely portrait of the predator’s size and shape.

“It would’ve looked for all the world like a modern, gigantic shark, because this is the beauty of it,” Kear said. “This is a body model that has worked for 115 million years, like an evolutionary success story.”

A predator’s past could hint at the future

The study of the Darwin sharks suggested that modern sharks rose early in their adaptive evolution to the top of prehistoric food chains, the researchers said.

Now, scientists could scour similar environments worldwide for others, Kear said.

“They must have been around before,” he said. “This thing had ancestors.”

Studying ancient ecosystems like this one could help researchers understand how today’s species might respond to environmental change, Kear added.

“This is where our modern world begins,” he said. “By looking at what happened during past shifts in climate and biodiversity, we can get a better sense of what might come next.”