Scientists have uncovered evidence of a colossal shark that lived off northern Australia about 115 million years ago, revealing that modern shark lineages grew to immense sizes far earlier than expected.
Rare vertebrae from rocks once part of the ancient Tethys ocean show that this early lamniform predator shared the seas with giant marine reptiles during the Age of Dinosaurs.
Early Modern Sharks and Their Ancient Origins
Sharks are well-known ocean predators, and their lineage stretches back more than 400 million years. The ancestors of today’s shark groups, however, began to appear during the Age of Dinosaurs, with the earliest fossils of these modern lineages dating to roughly 135 million years ago.
These early forms, called lamniforms, were relatively small at around 1 m in length. Over millions of years, they eventually diversified into enormous species, including the well-known ‘Megalodon’, which may have reached lengths of more than 17 m, and the modern Great White shark, an apex predator that grows to about 6 m.
Why Shark Teeth Dominate the Fossil Record
Sharks have skeletons made of cartilage rather than bone, so most of their bodies do not fossilize easily. As a result, their fossil record consists mainly of teeth, which are shed continuously during feeding. These teeth often accumulate in ancient seafloor sediments. They are regularly found in the same layers as the bones and teeth of fishes and the enormous marine reptiles that ruled many prehistoric oceans.
A Fossil Hotspot Along the Ancient Tethys Ocean
The rocky coastal area near the city of Darwin in northern Australia was once part of the muddy bottom of the Tethys ocean, a vast waterway that extended from Gondwana (now Australia) to the island regions of Laurasia (now Europe).
Numerous remains of ancient marine life have been discovered in this region, including plesiosaurs (long-necked marine reptile resembling the popular image of the Loch Ness monster), ichthyosaurs (‘fish-lizards’), and large bony fish. Among these finds, several exceptionally large vertebrae stand out because they point to a previously unknown giant lamniform shark.
Vertebrae Reveal a Massive Early Cardabiodontid
Five vertebrae were recovered, each partially mineralized, which helped them survive through time. Their shape closely matches the vertebrae of modern Great White sharks. However, while adult Great Whites typically have vertebrae about 8 cm wide, the vertebrae from the Darwin specimen measured more than 12 cm across. Their distinctive features identify them as part of the cardabiodontid group, which consists of huge predatory sharks that lived around 100 million years ago.
The Darwin shark is especially significant because it appears to be about 15 million years older than other known cardabiodontids and had already reached the large body size characteristic of the group.
Reconstructing the Size of an Early Mega-Predator
To determine how large this early modern shark might have been, a broad international team of scientists collaborated on a detailed analysis. The group included paleontologists and tomographic specialists from the U.S.A., Sweden, and Australia, along with ichthyologists from South Africa and the U.S.A.
The paper was published in the Nature portfolio journal Communications Biology. Ancient shark fossils from the Age of Dinosaurs are on public display at the Swedish Museum of Natural History.
Reference: “Early gigantic lamniform marks the onset of mega-body size in modern shark evolution” by Mohamad Bazzi, Mikael Siversson, Sabine Wintner, Michael Newbrey, Jonathan L. Payne, Nicolás E. Campione, Aubrey J. Roberts, Lisa J. Natanson, Stephen Hall, Tatianna Blake and Benjamin P. Kear, 25 October 2025, Communications Biology.
DOI: 10.1038/s42003-025-08930-y
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