Fossils discovered near Darwin, Australia, indicate a colossal shark lived in northern Australian seas around 115 million years ago. This early lamniform shark reached gigantic sizes much sooner than previously thought, sharing the ocean's top predator role with marine reptiles during the dinosaur age. The findings challenge earlier understandings of shark evolution.
Approximately 115 million years ago, during the Cretaceous period, the ancient Tethys Ocean covered what is now northern Australia. The seafloor near modern-day Darwin yielded remains of diverse marine life, including plesiosaurs, ichthyosaurs, and large bony fish. Among these, five partly mineralized vertebrae stand out, measuring over 12 cm in diameter—larger than those of an adult great white shark, which are about 8 cm wide.
These vertebrae belong to a cardabiodontid shark, a group of giant predators known from around 100 million years ago. This specimen, however, dates back 15 million years earlier, marking the onset of mega-body sizes in modern shark lineages. Modern sharks evolved from ancestors over 400 million years old, with lamniforms emerging around 135 million years ago at lengths of about 1 meter. Over time, they grew into giants like the megalodon, exceeding 17 meters, and the great white, reaching 6 meters.
Shark fossils are rare due to their cartilage skeletons, leaving mostly teeth as evidence, which accumulate on ancient seabeds. A multidisciplinary team from the USA, Sweden, Australia, and South Africa analyzed the vertebrae using tomography and other methods to estimate the shark's size. Their research, published in Communications Biology in 2025, highlights how these early sharks competed with dinosaur-era marine reptiles for dominance.
The fossils are now housed at the Swedish Museum of Natural History, offering public insight into prehistoric ocean ecosystems. This discovery revises timelines for shark gigantism, showing modern-type predators achieved enormous scales amid the Age of Dinosaurs.