Never mind bats and birds, pterosaurs were the first real evolutionary heroes who gained the ability of powered flight. While often mistaken for dinosaurs, pterosaurs are actually more like their cousins. Being a bit of an evolutionary marvel, with their thin membranous wings, fragile skeletons, and long, pointed beaks, they have become quite a fascinating group to study the ecology of.
One of the most fascinating things that the fossil record can show us is evidence of feeding relationships. If you think about it, this is far more exciting than just finding skeletons. While the bones of animals might tell us more about how an animal died, it is the study of trace fossils – like trackways or burrows – that tell us what an animal was doing while it was actually alive.
For pterosaurs, such evidence in the fossil record is extremely rare, and we only have small glimpses into how these animals actually behaved. When it comes to diet, we know very little. Previously, researchers have carefully reconstructed the anatomy of pterosaurs and compared them with modern animals like birds to carefully infer what they might have fed on. For example, having long spiky teeth would have made perfect fishing hooks. Beyond inference though, there is little direct evidence of what they fed on. Some giant pterosaurs might have even fed on small dinosaurs!
Now for the first time, the fossilised poop (coprolite) of a pterosaur has been discovered with direct and identifiable remains of other animals. They come from the Wierzbic Quarry in Poland, near to the Holy Cross Mountains, and date to the Late Jurassic period around 160 million years ago.
Researchers fired up a powerful visualisation tool called a synchrotron, which is able to help measure and view even the smallest particles within materials. In this case, fossil poop. The details it produces are exquisite, allowing researchers to visually reconstruct the contents of the pterosaur’s pre-poop meal.
What the researchers found was a small medley of marine animals. The digested remains of bivalves, ostracods, gastropods, and other small crustaceans and arthropods were discovered. As well as some small bristles that might have belonged to polychaete worms.
Intriguingly, these fragments were contained within a poop-matrix comprising mostly foraminifera – small, microscopic and shelled protists. And too many of them just to be there by mistake, suggesting that our little flying friend was consuming them deliberately.
As such, this provides the first direct evidence of a pterosaur that probably utilised filter feeding as a feeding mode. Possibly species known from the same region include Gnathosaurus and Ctenochasma. Both of these show anatomical evidence that could indicate filter feeding, including an elongated beak, and many closely-spaced teeth to act like a sieve.
Such a feeding style is also known for the modern flamingo, whose droppings have also been examined (for science) and with evidence of foraminifer found.
“The similar contents of the droppings of these flamingos and the pterosaur coprolites could be explained by similar feeding environments and mesh sizes of the filter-feeding apparatus. It appears therefore that the pterosaurs which produced the footprints and droppings found in Poland were indeed the flamingos of the Late Jurassic,” says Martin Qvarnström, lead author of the study.
So, for any palaeoartists reading this, you now have full scientific license to start painting pink pterosaurs.
2019. Filter feeding in Late Jurassic pterosaurs supported by coprolite contents. PeerJ 7:e7375 https://doi.org/10.7717/peerj.7375