Scientists have obtained chemical evidence for the first time that pterosaurs ate fish and squid

An international team of geochemists and paleontologists led by Curtin University (Australia) has discovered a rare combination of preserved soft tissue, minerals and molecular biomarkers in the wing phalanx of a 113-million-year-old pterosaur, providing the first direct chemical evidence of the flying lizard's fish and squid diet.

The fossil was found in the Romualdo Formation in the Araripe Basin in northeastern Brazil, an area famous for the exceptional preservation of Cretaceous vertebrates. The bone belongs to a pterosaur from the family Anhangueridae and is encased within a carbonate nodule, which means it is preserved in three dimensions along with collagen fibers, minerals and lipid molecules.

Scientists found that the decomposition of the pterosaur's body did not take place under typical oxygen-free conditions, as previously thought, but in a local acidic and oxidizing microenvironment around the carcass. This environment resulted from bacterial activity and stimulated the early formation of the phosphate mineral fluorapatite, which fixed and stabilized the tissues at a very early stage of decomposition. Near fluorapatite, barite and celestine were found - minerals indicating the active work of sulfur bacteria in this microzone.

After phosphatization, the bone went through three more successive stages of mineralization with calcium carbonate, which literally imbedded the organic molecules within the mineral layers and protected them from further destruction over millions of years. It was this multi-stage “packaging” - a rare combination of processes that usually occur separately - that, according to the authors’ conclusions, became the key to the preservation of biomolecules over such a gigantic time period.

The most unexpected result was the biomolecules themselves: steroids were found in the bones, including cholesterol, the carbon isotope composition of which indicates feeding on fish and cephalopods - squid and octopus. This is the first direct molecular evidence of a pterosaur's diet, obtained not from stomach contents or dental analysis, but from chemical traces preserved directly in the bone tissue.

The authors note that they have already recorded a similar mechanism of multi-stage mineralization in other fossils - fish from the Green River Formation in the USA and an ichthyosaur from the Posidonia Shale in Germany - that is, we can talk about a more universal path of fossilization that occurs in different eras and environments. Understanding this mechanism, according to the researchers, will help to find and correctly interpret other equally rare finds with preserved soft tissues and molecules.