Rare Fossil Reveals a Three-Tier Food Chain Frozen in Time: a Pterosaur Eaten by an Ichthyosaur Eaten by a Pliosaur

Uncovered in part by amateur fossil hunters in Australia, the fossil preserves a unique look at prehistoric predatory dynamics This illustration shows an ichthyosaur biting a pterosaur, with a pliosaur preparing to attack from below. Peter Trusler Roughly 100 million years ago, a swimming ichthyosaur chowed down on a flying pterosaur. But not long after finishing its meal, the predator was then partially eaten by the “T. rex of the ocean,” an enormous reptile known as a pliosaur. That’s the chain of events scientists have pieced together from a rare Early Cretaceous fossil that appears to show a three-tier predator interaction—or, as IFLScience’s Eleanor Higgs puts it, a “three-way chomp fest.” The unique fossil, described in a paper published July 27 in Gondwana Research, deepens paleontologists’ understanding of the prehistoric creatures and their environment. “[It is] a marine reptile crime scene, and it did take a bit of working out to tell that story,” lead author Matt White, a paleontologist at the University of New England in Australia, tells the Australian Broadcasting Corporation’s Abbey Halter. Three-dimensional imaging techniques allowed the scientists to peer inside sphere-like rock nodules found with the ichthyosaur fossil, which they suspect were its stomach contents. Dinosaur Experiences Australia The modern saga of the fossil began in August 2019, when recreational fossil hunters Mike and Cathy Freeman and Gary and Barb Flewelling stumbled upon several large bones near Richmond, a town in the outback interior of Queensland, in northeast Australia. They were digging at a “fossicking” site, a designated area where members of the public can search for gems, stones, minerals and some fossils with a license. They donated the mysterious creature’s remains to the local Kronosaurus Korner museum, where staff affectionately referred to them as B.O.B., short for “bag of bones.” Three years later, museum curator Kevin Petersen returned to the fossicking site to see what else he could find. Petersen unearthed the rest of the skeleton and realized it was a massive ichthyosaur, an air-breathing, ocean-dwelling reptile that looked like a cross between a crocodile and a dolphin. In life, scientists think the animal, a member of the Platypterygius australis species, was between 19 and 23 feet long. Did you know? Pregnant ichthyosaur In 2009, scientists unearthed the fossilized remains of a pregnant ichthyosaur in what is now Chile. Researchers published an analysis of the fossil last year, and a later CT scan revealed the animal had not one but two fetuses. Today, Queensland’s outback is flat, dry, hot and dusty. But between 95 million and 120 million years ago, during the Early Cretaceous, the region was underwater. At the time, the shallow, inland Eromanga Sea covered roughly a third of Australia, creating a rich marine environment teeming with ancient reptiles that swam the seas and soared overhead, as well as fish and other aquatic life. When researchers took a closer look at the ichthyosaur’s skeleton, they found signs the creature had suffered grievous injuries: split vertebrae, missing ribs and bones with large bite marks. The only creature that would have been capable of inflicting such damage was a pliosaur, a powerful, carnivorous, crocodile-like marine reptile. More specifically, the scientists think the pliosaur was a Kronosaurus queenslandicus, an apex predator with crushing teeth. “They’re quite a formidable animal—basically the T. rex of the ocean,” White tells the Australian Broadcasting Corporation. Staff and volunteers spent more than 600 hours preparing the specimen, nicknamed "B.O.B." which has been donated to the Kronosaurus Korner museum. Dinosaur Experiences Australia Researchers suspect a pliosaur preyed on the ichthyosaur, then left behind a mangled carcass that eventually drifted to the seafloor, where it was entombed in mud and preserved for millennia. During their examination, the scientists found peculiar, spherical masses near the ichthyosaur’s skull, according to a statement about the discovery. Three-dimensional imaging later revealed what was inside: bits of fish, cephalopods and a few bones of a pterosaur, a large, flying reptile that ruled the skies between about 66 million and 228 million years ago. The team suggests these were the remnants of the ichthyosaur’s stomach contents, which likely ended up near its head after the violent pliosaur attack. Before being chomped by the pliosaur, the ichthyosaur may have snatched the pterosaur out of the air as it dropped to the water to catch a fish. Another possibility is that the ichthyosaur stumbled upon an already dead pterosaur and took advantage of an easy meal. Either way, scientists say the fossil is the first known example of a pterosaur being eaten by an ichthyosaur. The ichthyosaur’s “impressively varied” stomach contents suggest it was a “super-scavenger of the seas, not fussy about what it ate and happily hoovering up the dead, the dying and the decaying, including pterosaurs,” David Unwin, a paleobiologist at the University of Leicester in England who was not involved with the study, tells New Scientist’s James Urquhart. You Might Also Like Get the latest stories in your inbox every weekday. More about: Animals Australia Bones Fossils New Research Oceans Prey and Predators Reptiles