Paleontologists from China and Brazil have reported the discovery of 320 phytoliths (tiny mineral structures formed within plant cells) found in the fossilized stomach of a pterosaur species known as Synopterus atavismus.
Pterosaurs, a group of reptiles that went extinct during the Mesozoic Era, were the first vertebrates to develop powered flight.
However, their dietary habits remain largely enigmatic.
Various hypotheses have been proposed regarding pterosaur diets, including insectivorous, piscivorous, carnivorous, omnivorous, herbivorous/frugivorous, filter feeding, and generalized diets.
Though stomach contents provide compelling evidence, such finds are exceedingly rare.
In addition to scales associated with the thorax of Eudimorphodon, only five confirmed instances of pterosaur gastric contents have been documented since the Late Triassic in Italy, all related to Rhamphorhynchus from the Late Jurassic Solnhofen limestone in Germany.
These instances largely consist of remains like dead fish, along with some unidentified items.
In a recent study, Dr. Xiaolin Wang from the Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, and colleagues investigated the contents of fossilized stomachs from Synopterus atavismus, which existed in China approximately 120 million years ago.
They identified numerous small gastroliths in the stomach contents, from which they extracted 320 phytoliths.
“Phytoliths are microscopic silica structures formed during plant growth, exhibiting diverse morphologies across different plant species and even within various parts of the same plant,” the paleontologists stated.
“This discovery marks the first extraction of phytoliths from a pterosaur and the second documented instance of a pterosaur featuring a gastrolith.”
Specimen of Synopterus atavismus. Image credit: Jiang et al., doi: 10.1016/j.scib.2025.06.040.
To determine whether Synopterus atavismus was indeed herbivorous, the researchers explored other possible interpretations.
“Initially, we confirmed that surrounding rocks did not contain the phytoliths found in the stomach, eliminating contamination as a factor,” the researchers commented.
“We also considered the possibility that the plant material could have originated from animals that consume plants.”
“However, Synopterus atavismus exhibited a rapid metabolism akin to that of birds. If it had consumed vertebrates or insects, traces like bones, scales, or hard insect shells would have been present in the stomach, but none were found.”
“The hypothesis of eating soft-bodied creatures like caterpillars was also insufficient. Why would it require so many gastroliths if hard food wasn’t part of its diet?”
“These stones typically assist in breaking down tough materials such as insect shells and plant matter, making them unneeded for softer prey.”
“Lastly, prior research suggested that Tapejara wellnhoferi, a close relative of Synopterus atavismus, had robust jaws adapted for consuming plants, reinforcing this conclusion.”
“Thus, phytoliths clearly indicate direct dietary intake, while gastroliths were utilized as tools for grinding plant material.”
The team’s paper is published in the October 15, 2025 issue of the journal Science Bulletin.
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Jiang Shunxin et al. 2025. First phytoliths discovered in pterosaurs – evidence of herbivory. Science Bulletin 70 (19): 3134-3138; doi: 10.1016/j.scib.2025.06.040
Source: www.sci.news
