A Cretaceous congregation
In the arid interior of northeastern Brazil lies the Araripe Basin, a geological depression containing one of the world's most important fossil deposits. The rocks here, specifically the Crato and Romualdo Formations of the Santana Group, date back to the Early Cretaceous period, around 113 to 110 million years ago. This basin was once a complex system of lakes and lagoons, and the unique chemical conditions of the water led to the exceptional preservation of countless organisms. This type of fossil site is known to paleontologists as a Lagerstätte.
The Araripe Basin is known for its diversity of pterosaurs, the flying reptiles of the dinosaur era. Fossils of species like Tapejara and Thalassodromeus are found here, often with soft tissues like crests and membranes preserved. The strongest evidence of pterosaur social life comes from finds that strongly suggest colonial nesting. Discoveries of concentrated eggshell fragments and the scattered bones of very young, juvenile pterosaurs in specific layers indicate these areas were nurseries. This suggests that, much like modern seabirds, some pterosaur species gathered in large groups to lay eggs and raise their young.