Paleotologists from China and Brazil say they found a total of 320 phytoliths – microscopic solids made up of mineral deposits that form inside plant cells – inside the fossilized stomach of a species of pterosaur called Synopterus atavism.
Pterosaurs, a group of extinct reptiles from the Mesozoic era, were the first vertebrates to develop powered flight.
Among several questions regarding these flying reptiles are their feeding habits, which remain poorly understood.
Various dietary hypotheses have been proposed for different groups of pterosaurs, including insectivorous, piscivorous, carnivorous, durophagous, herbivorous/frugivore, filter-feeding, and generalist diets.
As is widely accepted, the conclusive evidence is the stomach contents, which are extremely rare.
In addition to the presence of scales associated with the thorax Eudimorphodon from the Late Triassic in Italy there are only five confirmed cases of pterosaur stomach contents, all associated with Rhamphorhynchus from the Late Jurassic Solnhofen Limestone in Germany.
They mainly consist of fish remains and some unidentified objects.
In a new study, Dr. Xiaolin Wang from the Institute of Vertebrate Paleontology and Paleoanthropology of the Chinese Academy of Sciences and colleagues examined fossilized stomach contents Synopterus atavisma species of tapejarid pterodactyloid pterosaur that lived in China about 120 million years ago.
They found numerous small gastroliths in the stomach contents and extracted 320 phytoliths from a small piece of the contents.
“Phytoliths are microscopic silica structures formed during plant growth and exhibit different morphologies in different plant species and even in different parts of the same plant,” the paleontologists said.
“This discovery marks both the first recovery of phytoliths from any pterosaur and the second documented pterosaur specimen to contain gastroliths.”
Sample Cuntimely atavism. Image credit: Jiang etc.., two: 10.1016/j.scib.2025.06.040.
To confirm this Synopterus atavism was indeed a herbivore, researchers looked for other possible explanations.
“First, we ruled out contamination by showing that the surrounding rock does not contain any of the phytoliths found in the stomach,” they said.
“We next looked at whether the plant material could have come from eating other plant-eating animals.”
“But Synopterus atavism “He had a fast metabolism like a bird – if he had eaten vertebrates or insects, there would have been some traces left in his stomach, such as bones, scales or hard insect shells, but there were none.”
“The idea that it feeds on soft creatures like caterpillars also doesn't hold water: why does it need so many stones in its stomach if it doesn't grind up tough food?”
“These rocks are typically used by animals to break down hard materials such as insect shells or plants, making them unnecessary for digesting soft prey.”
“Finally, earlier studies Tapehara Wellnhoferi – close relative Synopterus atavism “showed that it had strong jaws adapted for eating plants, further supporting this conclusion.”
“Therefore, phytoliths represent a direct diet, and gastroliths function as grinding tools in processing plant material.”
teams paper published in the October 15, 2025 issue of the magazine. Scientific Bulletin.
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Shunxing Jiang etc.. 2025. The first appearance of phytoliths in pterosaurs is evidence of herbivory. Scientific Bulletin 70 (19): 3134-3138; two: 10.1016/j.scib.2025.06.040
