Like Owls, Some Prehistoric Flying Reptiles May Have Regurgitated Pellets

The discovery of vomited projectiles from two pterosaurs provides new clues about the its diet and digestive system

Two fossilized pterosaurs with pellets
Scientists examined two Kunpengopterus sinensis specimens. The green arrows indicate the pellets and the yellow arrows indicate the isolated fish scales. Jiang et al., Philosophical Transactions of the Royal Society B, 2022

Researchers in China have discovered that, much like modern-day owls, an extinct species of pterosaur may have vomited pellets containing parts of its meal it couldn’t digest. The find provides new clues about the flying reptile’s diet and digestive system.

In a study published in Philosophical Transactions of the Royal Society B, scientists examined two pterosaurs, one adult and one juvenile, of the species Kunpengopterus sinensis. They found fossilized pellets containing fish scales of an unknown species outside their bodies. Per the study, the larger pellet was wider than both pterosaurs’ pelvises, suggesting it could not have exited through the cloaca, a multi-functional exit many animals have for defecating, mating, or laying eggs.

“We have two specimens of one species, with similar-size pellets relative to its body size. This does not often happen in the study of vertebrate paleontology, especially pterosaurs,” study author Shunxing Jiang, a paleontologist with the Chinese Academy of Sciences, tells the New York Times’ Asher Elbein. 

The pellets indicate “the presence of two-part stomachs and efficient antiperistalsis in both juveniles and adults,” per the study. Antiperistalsis is the contraction of the intestines that forces contents the opposite direction than toward the mouth like usual. Generally, animals need both features to regularly produce pellets, per the Times

The two Kunpengopterus specimens, found in northeast China's Yanliao Biota, were from the Late Jurassic period, per the study. Jiang tells the Times that evidence of a two-part stomach has been seen in at least one Cretaceous pterosaur, but pellets from earlier pterosaurs could mean that this feature evolved millions of years earlier.

All modern-day birds have two-part stomachs. In owls, this second chamber, called the gizzard, collects bone, teeth and fur, which is later expelled. Like owls, pterosaurs did not chew their food. 

“Most pterosaurs cannot chew their food because their teeth did not have the structure for chewing. Also, some nearly complete fish were found in the stomachs of pterosaurs and it is apparent that the fish were not chewed,” Jiang tells Live Science’s Kevin McSpadden.

The regurgitation of prey parts is common in modern-day owls and raptors, and it also happens in gulls, cormorants, crocodilians, certain lizards and some marine mammals, the study states. Extinct species, like non-avian dinosaurs—a close relative of pterosaurs—and other reptilian species also coughed up pellets, leading scientists to previously think pterosaurs did the same, per the study. 

The Kunpengopterus pellets may suggest a “more extensive distribution of this digestive strategy in flying reptiles, which adds credence to the hypothesis that a two-part stomach is common to all archosaurs,” the study states. Archosaurs are a group of reptiles that include modern-day crocodiles, birds and extinct reptiles, such as dinosaurs and pterosaurs. 

The presence of fish scales in both juvenile and adult pterosaur pellets also indicates that the reptile likely ate the same food—primarily fish—throughout its life, though adults were likely able to eat much larger animals, per the study.