A Graveyard for flying reptiles
In the Araripe Basin of northeastern Brazil lies a geological unit called the Romualdo Formation. Dating to the Early Cretaceous period, approximately 110-113 million years ago, its layers hold one of the world's most detailed collections of pterosaur fossils. This location is a Lagerstätte, a sedimentary deposit with extraordinary fossil preservation. The unique conditions of a coastal lagoon, with low-oxygen water and rapid mineralization, preserved bone and soft tissues as well.
The most famous pterosaur from this formation is Anhanguera, a genus of fish-eating flying reptiles. The name comes from the Tupi language and means "old devil." The type species, Anhanguera blittersdorffi, had a wingspan of about 4.5 meters (15 feet). Its long skull, up to 60 cm in length, featured distinctive semicircular crests on the top and bottom of its snout and a fearsome set of conical teeth perfect for snatching fish from the proto-Atlantic ocean. These pterosaurs are found encased in limestone nodules, which miners and paleontologists split open to reveal the three-dimensionally preserved skeletons inside.
Preserved in stone
The preservation quality in the Romualdo Formation is exceptional. Paleontologists have identified fossilized muscle fibers, collagen-like fibers, and even the impressions of blood vessels on wing membranes. This level of detail shows the biology of these flying animals. Recent studies have detected traces of steroids, a type of organic molecule, within a 113-million-year-old pterosaur wing fragment.
This molecular evidence confirms what the skeletal anatomy suggests: Anhanguera had a diet of marine life. Carbon-isotope measurements point to a diet of fish and cephalopods, like squid. The ultimate proof of their diet comes from fossilized stomach contents, known as bromalites, and even fossilized vomit, or regurgitalites. One such fossilized regurgitation from an unidentified predator contained the remains of two small filter-feeding pterosaurs and four fish, recording a Cretaceous food web. Besides Anhanguera, the formation has yielded other pterosaurs like the massive-crested Thalassodromeus and Tupuxuara, showing a diverse pterosaur ecosystem.