[grey_whiskers]

Perhaps these critters used all four limbs for flight because they had not evolved enough strenght and power to generate lift with just one pair of limbs.

More steroids!

Full Disclosure: That's cool as far as it goes, but then you need *retrograde* evolution of the hind limbs back into legs as the front wings get stronger.

Cheers!

[b_sharp]

"Full Disclosure: That's cool as far as it goes, but then you need *retrograde* evolution of the hind limbs back into legs as the front wings get stronger."

Not a problem. Features lose function all the time. Think Cetacean.

For those that don't know and the lurkers: The measure of evolution is not whether certain features gain or lose function but how much the change, any change, affects future ability to pass on genes. If a reduced function increases the number of successful offspring, that organism has a higher fitness and the reduced function will be retained. As long as the costs of a change are less than benefits of the change that change is an advantage.