Pterosaurs flew before birds—and wore fuzzy pycnofiber coats
Pterosaurs were warm-blooded flying reptiles of the Late Triassic to end-Cretaceous (about 228–66 million years ago)—the earliest vertebrates known to evolve powered flight. They are not dinosaurs, though closer to birds and other dinosaurs than to lizards, and popular media still mislabels them “flying dinosaurs.”
Pterosaurs flew through most of the Mesozoic, spanning the Late Triassic up to the Cretaceous's end, about 228 to 66 million years ago, and were the first vertebrates known to achieve powered flight. Each wing was a membrane of skin, muscle and other tissue stretched from the ankle to an enormously elongated fourth finger. Popular culture calls them flying dinosaurs or pterodactyls, but dinosaurs are defined as descendants of the common ancestor of Saurischia and Ornithischia, which leaves pterosaurs out. Their lineage sits nearer to dinosaurs and birds than to crocodiles or other surviving reptiles, yet they did not give rise to birds; strictly, pterodactyl refers to the genus Pterodactylus or the suborder Pterodactyloidea.
Palaeontologists traditionally sort them into two grades. The early, non-pterodactyloid forms were modest, with wingspans up to two metres, teeth along the whole jaw and usually long tails, and their broad wing membranes probably joined the hind legs. Short hand bones gave them a clumsy sprawl on the ground, but strong claws made them good climbers, and some may have lived in trees. They ate insects, fish and small land animals.
Later pterodactyloids diversified into many sizes and lifestyles. They had narrower wings leaving the hind legs free, tiny tails and big heads on long necks. Long hand bones let them walk well on all fours with an upright stance, flat on the hind feet, the wing finger folded up out of the way.
Their bodies and parts of their wings were covered in hair-like pycnofibres, from simple strands to branching down that may share an origin with dinosaur feathers, hinting that early feathers arose in the pair's common ancestor, possibly for insulation. They were warm-blooded, with efficient one-way breathing through air sacs that hollowed their bones. Adult sizes ranged from the tiny anurognathids to Quetzalcoatlus and Hatzegopteryx, whose wingspans reached at least nine metres, the largest flying animals known.
Source: Pterosaur
