On pterosaur wing development
So, with Mark Witton’s book out, and with my idea in restrospective failing on the account that warm blooded metabolisms would have probably been necessary prior to flight itself, I still have one thing to say about how pterosaurs went up in the air.
It seems very likely that gliding altogether was probably not how flight evolved in tetrapods, as bats seemingly began as flutters and early birds don’t seem particularly adapted for climbing. Pterosaurs, of course, coud had been the exception; after all, what else would motivate a glider to fly than the dry environments of the Triassic?
Nonetheless, in previous discussions, the idea that the wing finger actually began as a display device rather than something used for gliding has intrigued me. It would explain the unique wing finger retraction in pterosaurs – rather than an adaptation acquired to deal with progressively larger wing fingers, it would have predated flight as a way to keep the displaying membrane safe – and why flight would have evolved how it did: as the membrane expanded up the arm, the fifth finger, if still present, would be excluded and removed, and the presence of muscles in the membrane would have started since the very beginning, as means to expand and retract the signals in the membrane. It would also explain why pterosaurs took to the air so quickly: with such exadaptations, all you’d need would be extending the membrane along the body.