Microbes destroyed the ancient pterosaur’s wing bone, then preserved it for 100 million years

More than 100 million years ago, a flying reptile called a pterosaur flew over the oceans to hunt squid and fish.

Recently, one of its wing bones was discovered in Brazil, and over the eons it transformed into a fossil composed of a complex array of different chemicals and minerals.

And in New research published in iScienceMy colleagues and I have found that fossil bone still holds the secrets of this creature’s life, including the microscopic internal structures of its bones and molecular traces of its biology and diet.

Fossil treasure from Brazil

The fossil comes from the Romualdo Formation in the Araripe Basin in northeastern Brazil, one of the largest in the world. The most interesting fossil deposits. The site contains exquisitely preserved fish, turtles and crocodile relatives Pterosaurs.

Many fossils of the Romualdo Formation are preserved within rounded rock nodules known as carbonate concretions. These mineral structures form soon after burial, effectively isolating the remains from the environment. Think of them as natural time capsules.

Our fossil is a hollow wing bone, or phalanx. Pterosaur bones were thin and lightweight to aid flight, so they are rarely preserved in such detail.

Using a high-resolution CT scan, we examined the inside of the bone without breaking it. Scans revealed layers of minerals of varying densities filling the cavity, evidence of a complex series of chemical events that preserved the bone. We used several other methods to identify minerals.

Microbes aided in decomposition and preservation

The exceptional preservation of the fossil may have begun with the decay. When the pterosaur’s body decomposed on the ancient sea floor, microbes broke down the tissue and… Changes in sediment chemistry. These changes led to the rapid formation of phosphate minerals.

One mineral in particular, called fluorapatite, forms in and around bones, stabilizing delicate features before they are lost. Under a microscope, we can still see the microscopic channels that once carried nutrients through living tissue.

Mineralogical analysis revealed evidence of microbial activity. We discovered barite and celestite, minerals associated with bacteria that use sulfur. These microbes drove chemical reactions that helped create the conditions necessary for preservation.

In other words, ancient microbes not only decomposed the body, but also helped preserve it for science.

A metal vault for ancient molecules

After early phosphate minerals stabilized the bone, a series of calcite layers gradually formed in and around the bone. These are largely derived from carbon released during the breakdown of adipose tissue.

First, a thin layer of fine-grained calcite forms along the bone surface, followed by a second, slightly coarser-grained layer. Over a longer period of time, larger calcite crystals formed, eventually filling the bone cavity.

Analysis showed that this calcite contained a low percentage of an isotope called carbon-13, suggesting that it came partly from organic carbon sources, such as fatty lipids and residual bone material. In contrast, any organic matter remaining in bones appears to contain relatively high levels of carbon-13.

The multi-layered mineral barrier served as a geological vault, protecting delicate structures and organic compounds trapped in the bones from chemical decomposition for millions of years. This protection allowed molecular tracers such as steroid biomarkers and collagen fiber patterns to survive, giving us a rare window into the biology and diet of these ancient flying reptiles.

Molecular traces of ancient life

Within this mineral structure, we discovered molecular traces of life called steranes, which are derived from steroid lipids that were once present in living cells. To our knowledge, this is the first time steroid biomarkers have been reported from a pterosaur fossil.

What’s even more exciting is that these molecules carry nutritional clues. Carbon isotope analysis of cholesterol-derived compounds suggests that this pterosaur likely fed on it Fish or squid-like marine animalsThis is what we expect from the shape of its teeth and skull.

The fossil also preserves microscopic structures Similar to collagen fibersThe protein framework that strengthens bones. Although they have changed chemically over millions of years, Fiber patterns remain visible They resemble those found in modern birds, which are distant relatives of pterosaurs.

Reading fossils in new ways

Discoveries like this change the way we study fossils. Instead of examining only bone shapes, we can now recover chemical and molecular signatures as well.

Understanding how these exceptional fossils formed may help identify other specimens capable of preserving ancient biomolecules. More broadly, our findings show that, under the right conditions, molecular traces of life can persist for more than 100 million years.

Even after millions and millions of years, ancient life could still leave behind chemical clues waiting to be discovered. As analytical techniques continue to advance and unusual preservation methods are better understood, there is an increasing potential to recover previously inaccessible information.

In the future, we may be able to discover ancient fragments of DNA or other molecular remains in exceptionally preserved fossils, including dinosaur and pterosaur fossils.