Pterosaurs were a large group of endothermic (warm-blooded) flying reptiles that lived alongside dinosaurs. They had hollow bones and elongated fourth fingers that helped form their wings.

Early pterosaurs were smaller, with toothed jaws, long tails and wings well-suited for active, agile flapping. Later species were larger, with (often toothless) beaks, reduced tails and a wide range of wing designs for different flight styles.