Spanning more than 160 million years across the fossil record, Pterosaurs were a diverse group of flying reptiles that dominated the skies of the Mesozoic Era. Juveniles of some species were as small as a bat or a modern bird, and others, such as Quetzalcoatlus, were the size of a giraffe with a wingspan topping out at 33ft (10m). Fossil evidence shows that at least some pterosaur species grew furlike "pycnofibers," or bristles, perhaps suggesting that these creatures were warm-blooded.

Pterosaurs have traditionally been roughly divided into two major categories or suborders: the rhamphorynchoids now often called basal pterosaurs, and the more advanced pterodactyloids. Rhamphorynchoids were small, short-necked, and long-tailed, while pterodactyloids were short-tailed, long-necked, longer-forearmed pterosaurs exhibiting a broader size range.

By the Late Jurassic Period, birds and pterosaurs overlapped extensively in many ecosystems. Some interpret this to suggest niche partitioning limited direct competition, while other scientists speculate that the decline of smaller pterosaurs coincided with a radiation of comparably sized birds during that interval which could indicate direct competition. This may also explain the larger body sizes seen among Pterosaurs of the Late Cretaceous, a change that may have doomed pterosaurs to extinction.