Modern sharks trace their origins to the Age of Dinosaurs, with the oldest known lamniform fossils dated to about 135 million years ago. These early sharks started small, around 1 meter in length, but later produced larger species including the Megalodon, which may have reached lengths up to 17 meters, and the Great White shark, now reaching about 6 meters.
Because sharks have cartilaginous skeletons, their fossils mainly consist of teeth. Fossil shark teeth are common in ancient seabed sediments and are found alongside remains of bony fish and marine reptiles.
The fossil site near Darwin, in northern Australia, was once part of the ancient Tethys ocean. Diverse marine fossils such as plesiosaurs, ichthyosaurs, and large fish have been discovered in this region. Notably, five partially mineralized vertebrae similar to those of modern Great Whites have been recovered. These fossil vertebrae, over 12 cm in diameter, significantly surpass the 8 cm width of adult Great Whites. Morphological analysis determined that the vertebrae belonged to a cardabiodontid shark - a group of mega-predators that lived about 100 million years ago. The Darwin specimen predates other cardabiodontids by 15 million years and already exhibited their hallmark large bodies.
To estimate the shark's true size, a team including paleontologists and tomographic experts from Sweden, the U.S.A., South Africa, and Australia collaborated on the reconstruction. The study is published in Communications Biology, and fossil specimens from the Age of Dinosaurs are exhibited at the Swedish Museum of Natural History.
Research Report: Early gigantic lamniform marks the onset of mega-body size in modern shark evolution
Related Links
Swedish Museum of Natural History
Explore The Early Earth at TerraDaily.com
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