The power of reptilian flight
Hello everyone! When I first started writing this, I went down a pretty big rabbit hole as I wanted to talk about the origins and development of flight. Ultimately, that is a BIG topic and as I went through my deep dive into deep time, I realized I could focus on one story of flight. Did you know that REPTILES were the first vertebrates to take to the air?
So, while today, the only flighted vertebrates we have around are birds and bats, before those groups of animals were around, reptiles successfully experimented with powered flight. These were the pterosaurs, which are NOT flying dinosaurs, contrary to popular depictions (birds ARE flying dinosaurs). Pterosaurs are a part of the Archosauria, the major group of reptiles that includes not only the pterosaurs, but dinosaurs (both avian and non-avian); modern crocodilians; the phytosaurs (crocodile-like semi-aquatic predators); aetosaurs (think of crossing a pig, a crocodile, and a spiky armadillo); the ornithosuchids (which have similarities to some carnivorous dinosaurs); and the diverse rauisuchids. Also, if you caught that in there and didn’t already know it, yes, the birds and crocodiles are each other’s closest living relatives!
Pterosaurs first appeared in the fossil record roughly 215-220 million years ago (mya) in the Triassic Period and were pretty small. Birds did not begin to appear until much later in the fossil record in the upper Jurassic (roughly 150 mya). Much like the dinosaurs on the ground, the pterosaurs really increased in diversity during the Jurassic and Cretaceous. By the time of their extinction along with the non-avian dinosaurs at the end of the Cretaceous, pterosaurs were the largest living animals before or since with the power of flight (wingspans of over 10 meters [~30 ft] have been estimated for some species).
So, they could fly, big deal! Birds and bats do it, what is so special? Well, I’d argue the first thing so special is that they, well, did it first! They also did it in a different way. Birds have hands (yes, they have hands…of a sort) that are essentially made up of fused finger and hand bones (to put it very simply). Lift is provided by their feathers (again, to put it VERY simply). Birds also have a distinctly lightweight skeleton that helps with flight (it’s actually a little more complicated than that … but I’ll let the bird folks field those questions). Bats utilize a thin skin membrane stretched over their arms and massively extended fingers to provide the lift to keep them aloft without feathers. The main structure of a pterosaur’s wing was their extremely long fourth finger (our “ring finger” if you will), while the other clawed fingers were still there to aid in terrestrial locomotion (non-flying pterosaur locomotion has been a subject of intense debate so we’ll just skip that for now). Stretched from the arm along this finger down to the rear limb was a membrane of skin that was strengthened by stiff fibers, as well as having muscle fibers that could adjust the tension and shape of the wing. Like birds, they also had incredibly lightweight skeletons. And just for fun and to add to how strange they are, they were covered in “pycnofibers.” What are pycnofibers? Well, they are the hair and/or feather-like covering of pterosaur skin. They’re not quite fur and they’re not quite feathers (although, there is some recent fossil evidence that they may in fact be a form of “proto-feather”) and they’re pretty unique to pterosaurs. NEAT!
I wish I had more time to talk about all of the really cool and strange features of pterosaurs in more detail, but this will have to do for now! I also wish we had some live pterosaurs to see, but luckily we do have a variety of other reptiles to see inside Scaly Slimy Spectacular!
Robert L. Hill
Associate Curator of Herpetology