Prehistoric Sharks Chowed Down on Pterosaurs

Prehistoric sharks were formidable foes. With their serrated teeth and girthy guts, species like Squalicorax, or crow sharks, likely made easy meals out of many fellow seafarers. But, as John Pickrell of National Geographic reports, a series of bite marks found on the wing bone of an 83-million-year-old Pteranodon shows that ancient sharks also sated themselves on beasts native to the sky.

The new discovery, published recently in the journal Palaios, not only expands the known palate of Cretaceous sharks, but also sheds some light on the (decidedly-not-dinosaurian) pterosaur way of life—and, perhaps, death.

Much of pterosaur biology has, to the frustration of paleontologists worldwide, eluded us, due in part to the delicate nature of their fragile, hollow bones, most of which, in the eons since these flying reptiles’ extinction about 66 million years ago, have been lost to time.

That’s part of what makes this “a very exciting find,” Michael Habib, a pterosaur expert at the University of Southern California who was not involved in the Palaios study, tells Pickrell. “Feeding traces on pterosaur bones are rare.”

Still, enough pterosaur fossils have surfaced to reveal their magnificent wingspans: For instance, this particular doomed specimen flapped with wings that stretched about 15 feet across.

At first glance, however, the leathery appendages of pterosaurs may not look like a particularly hearty option for a ravenous shark like Squalicorax, some species of which reached up to about 15 feet in length, Pickrell reports. But as contemporary carnivores can corroborate, wings often make for a tasty treat—especially when served slathered with buffalo sauce.

And, as it turns out, “pterosaurs actually had a lot of meat on their skeletons,” Habib explains to Pickrell. “The flight muscles in particular would have made a great meal.”

It’s for good reason: Those same flight muscles had quite the cargo to carry. Pterosaurs often had heads and necks “three or four times the length of [their] torsos,” Habib told Richard Conniff at National Geographic last year. This imbalance—which seems like it might handicap a creature meant to take to the skies—puzzled paleontologists for years. But more recent findings have shown just how powerful these reptilian wings evolved to be, rippling with thick muscles and blood vessels that helped them become airborne with sheer brute force.

But how might an aerodynamic pterosaur end up on the marine Squalicorax menu? Impressive sharks as they were, these toothy terrors probably weren’t spending much time aloft. As it turns out, there’s a decent chance that this pterosaur died close to shore, was washed away and got an inadvertent burial at sea, where it made a meandering shark very, very happy.

It’s also possible a particularly agile crow shark crested the surface of the sea to nab a low-flying specimen out of the air; after all, pterosaurs did include marine fish in their diet, and likely scoured the surface of the sea, Pickrell reports. But study authors Dana Ehret and T. Lynn Harrell believe this scenario is probably unlikely. The most convincing evidence against this? The tooth marks on the wing bone showed no signs of healing, indicating that the winged reptile was probably already dead by the time the shark was snacking. What’s more, this lucky Squalicorax wasn’t the only one to partake: Another set of bite marks was identified on the bone, this time belonging to a four- to six-foot-long barracuda lookalike called Saurodon, Pickrell reports.

This double-dining, featuring damage from the dentition of “two different groups of animals,” makes this fossil especially “unusual,” lead author Ehret, a paleontologist at the New Jersey State Museum in Trenton, tells Pickrell.

This builds the case for pterosaurs being a rather desirable Cretaceous culinary commodity. Their bones reveal that velociraptors and other scavenging or predatory dinosaurs noshed on these reptilian remains as well.

And Pteranodon wasn’t even the most impressive dish on the Squalicorax menu. Serrated Squalicorax tooth marks have been found on the bones of all sorts of hapless prehistoric dinosaurs, reptiles, and other fish—including gargantuan marine mosasaurs and land-dwelling hadrosaurs. Many of these particularly impressive finds were likely also scavenged, but in a dino-eat-dino world, early sharks (much like modern ones) probably weren’t too picky. When given the chance, these carnivorous fish took surf and turf to heart—and were chomping on far more than chum.

Katherine J. Wu | | READ MORE

Katherine J. Wu is a Boston-based science journalist and Story Collider senior producer whose work has appeared in National Geographic, Undark magazine, Popular Science and more. She holds a Ph.D. in Microbiology and Immunobiology from Harvard University, and was Smithsonian magazine's 2018 AAAS Mass Media Fellow.