During the age of dinosaurs, long before whales and modern sharks existed, a colossal shark inhabited the waters of what is now northern Australia. This creature was among the remarkable marine life of the Cretaceous period.
Researchers investigating a massive vertebra found on a beach near Darwin have identified it as the oldest known giant predator in the shark’s evolutionary lineage, existing about 15 million years earlier than previously identified large sharks.
And, let’s just say—it was impressive. The forebears of the modern-day great white sharks, which typically reach about 6 meters in length, are believed to have been around 8 meters long, according to the study published in Communication Biology.
“Cardabiodontidae were these ancient, massive predatory sharks that were quite prevalent from the Late Cretaceous onward—around 100 million years ago,” noted Benjamin Kjaer, a senior curator of paleontology at the Swedish Museum of Natural History and one of the study’s authors. He added that this discovery significantly pushes back the timeline for understanding the existence of these gigantic funagiodonts.
A Look Back: Fossils of a Giant Shark
Sharks boast a lineage that stretches back 400 million years, but the ancestors of modern great white sharks, known as oligarchs, surfaced in the fossil record about 135 million years ago.
Initially small—roughly one meter in length—the revelation that these giants had already emerged by around 115 million years ago caught researchers off guard.
The vertebrae were unearthed along Australia’s northern coastline near Darwin, remnants of a time when an ancient ocean spanned from Gondwana (modern-day Australia) to Laurasia (what we now think of as Europe).
This region is rich with fossils from prehistoric marine species, including long-necked plesiosaurs and ichthyosaurs.
Interestingly, the five vertebrae that triggered this search for the shark’s size weren’t recent finds. Kjaer mentioned they were previously overlooked, excavated back in the late 1980s and 1990s, measuring 4.7 inches in diameter, and had been stored in a museum for years.
Vertebrae serve as crucial tools for paleontologists studying ancient sharks. Because sharks’ skeletons are primarily composed of cartilage, the fossil record usually consists of teeth they lost throughout their life.
“Vertebrae are key because they provide insight into size,” Kjaer explained. “Trying to gauge scale from teeth alone is tricky. You might have big teeth paired with a small body or vice versa.”
The Enigma of Ancient Sharks’ Size
Scientists have relied on mathematical equations to estimate the dimensions of extinct sharks, including the notorious megalodon, which could have reached lengths of up to 56 feet, according to Kjaer.
However, the scarcity of vertebrae makes pinning down the sizes of these ancient sharks quite challenging.
A diverse team of researchers dedicated years to exploring various techniques to gauge the size of Darwin’s cardabiodontids, employing fishing data, CT scans, and mathematical modeling.
Ultimately, they crafted its profile, reflecting the predator’s likely size and shape.
“It would have resembled a modern giant shark, easily recognizable as one,” Kjaer stated. “This model has effectively thrived for 115 million years—an evolutionary achievement in itself.”
Understanding a Predator’s Past and Possible Future
The study of these ancient sharks indicates that modern sharks quickly rose to the top of the prehistoric food chain during their evolutionary journey, according to the researchers.
In the coming years, scientists hope to explore similar environments worldwide in search of other prehistoric remnants.
“They must have existed at some point,” he implied, “as they had ancestors.” Studying these ancient ecosystems could illuminate how existing species might adjust to ongoing environmental shifts, Kjaer suggested.
“This is where our contemporary world takes root,” he remarked. “By examining the impacts of past climate and biodiversity shifts, we can gain a clearer picture of what lies ahead.”
