A rare fossil discovery made in July 2023 at Dinosaur Provincial Park in Alberta, Canada, sheds light on ancient predator-prey interactions during the Cretaceous period. Researchers found a neck vertebra from a juvenile pterosaur species, Cryodrakon boreas, dating back 76 million years, which bears a 4-millimeter bite mark attributed to an ancient crocodilian.
The finding was published in the Journal of Paleontology.
The find provides the first direct evidence of an interaction between a crocodilian and a pterosaur in North America, a rare example of predator-prey interaction from the Cretaceous period.
Researchers believe the attacker was a crocodile of the species Leidyosuchus canadensis, which may have preyed upon the Cryodrakon boreas while it was alive or scavenged its body after death. "Pterosaur bones are very delicate, so finding fossils that have clearly been bitten by another animal is quite rare," said Dr. Caleb Brown from the Royal Tyrrell Museum of Palaeontology, according to Scienze Notizie.
It remains uncertain whether the pterosaur was alive or dead at the time of the bite and whether the bite mark was inflicted before or after its death. The young pterosaur likely had a wingspan of about 6.5 feet, and if it had survived to adulthood, its wingspan could have reached up to 33 feet. Cryodrakon boreas was one of the largest flying creatures in Earth's history and lived during the same period as dinosaurs, being among the largest beings in the sky.
To confirm the hypothesis of predation, researchers subjected the fossil to micro-CT scans, which ruled out other potential causes of the perforation, such as damage occurring during fossilization or excavation, according to SciencePost. The discovery of a well-preserved pterosaur bone, especially one bearing a bite mark, was exceptional, noted SciencePost. Pterosaur bones were hollow, essential for flight, and therefore not conducive to fossilization, making such finds exceedingly rare.
Similar discoveries have been made in Romania, where fossils of Azhdarchidae pterosaurs bore comparable bite marks, as reported by Scienze Notizie. These discoveries suggest that interactions between crocodiles and pterosaurs may have been more common than previously thought, despite being rarely documented.
Modern crocodilians are both active predators and scavengers, opportunistically feeding on a wide range of prey including small mammals, other reptiles, birds, and even carcasses left by other predators,. "They were probably similar in size to today's crocodiles," said Dr. Brian Pickles from Reading University.
"Most crocodilians feed at the surface of the water and are ambush predators, and many pterosaur species are thought to be tied to the water as well. Given this, if it was predation, it likely happened as an ambush at the water surface," said Brown. "There are several reasons why a pterosaur would be at the water surface, including drinking and hunting for food itself," he added.
The researchers noted that the puncture mark does not match the shape of the teeth of dinosaur predators in this region at the time, such as Gorgosaurus and Daspletosaurus. Instead, the puncture mark matched the shape of a crocodilian's tooth.
Cryodrakon boreas rivaled Quetzalcoatlus as the largest of the pterosaurs that inhabited North America at the time. Both Cryodrakon boreas and Quetzalcoatlus had heads with large toothless beaks, long necks, and short tails. "They were carnivorous, but researchers have disagreed as to their feeding strategy, with suggestions from carrion-feeding scavengers to aquatic probers to heron-like terrestrial stalkers," Brown said.
The article was written with the assistance of a news analysis system.