Racing Dinosaurs with Spoilers

PhilHibbs writes "The BBC is reporting a new theory - dinosaurs flapped their proto-wings to generate downforce for added traction when running up-hill. Another one to add to the many theories of the evolution of flight."

Comments

Re:Insect flight

[Simon Field]

Since evolution is still happening all around us, we can look at some of the "proto-wings" we see today and make some inferences.

We have squirrels that glide out of trees by stretching the skin between their legs.

We have snakes that do something similar.

We have flightless birds that still flap their wings when they run.

We have lizards that stretch membranes much like the flying squirrel. Some of them do it to glide, while others do it to control their temperature.

If feathers were only for flight, the flightless birds wouldn't have them, and flighted birds would only have them on their wings and tails. We use down for insulation in ski jackets for the same reason the goose made it in the first place.

A small, warm blooded dinosaur would need insulation. Insulation is lightweight for its bulk, so it would lower the density of the animal as a whole. This would protect the animal from falls, but it would also make it difficult to run, due to the air resistance overcoming the available traction.

Streamlining would be selected for. Small animals would experience higher Reynolds numbers (the air would seem thicker to them) and so flapping their feathered arms would get them more benefit than a larger animal would get.

It would not surprise me to find out that flight developed in several dinosaurs in parallel, given that we see it evolving in several quite different critters today (insects, reptiles, mammals, fish).

Your idea that flight developed as a side effect of temperature control mechanisms doesn't seem far-fetched to me at all. In fact, one might call it near-fletched, if one were a punning fellow.