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Perhaps THE hallmark of bat anatomy is the wing--a thin sheet of membranous skin attaching four of five fingers. But compared to another group of skin-winged fliers, that's pretty much it.

According to recent fossil evidence, pterosaur wings were not simple sheets of skin like bat wings were.

The pterosaur wing was unique. The main surface was a membranous structure, made up of muscle, skin, blood vessels and stiffening fibers.

Could this sort of anatomical complexity serve the batwing design more efficently, or would it be too much baggage?

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No, bats wings evolved specifically for them and their wings are very efficient already, some bats fly long ranges every day such as the local fruitbats here. Sizes of bats range from a tiny one in asia about the size of a large bumblebee which lives in bamboo to large fruit bats which can glide.

In this link there are bats that fly up to 250 miles (402 km) in a single night. They can fly up to 10,000 feet (3,048 m) high and reach speeds up to 60 miles per hour (97kph)

No advantage would be gained by making their wings heavier or changing their shape or composition to be like a pterosaur.

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Probably not.

Given that the mechanism of flight differs between pterosaurs and bats, the structural considerations also differ. Bats fly by constantly flapping their wings. The lightweight membrane between their wings needs to be as light as possible for this to be efficient. Extra rigidity provided by a thicker wing just adds extra weight for no benefit.

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Bat wings aren't as simple as you suggest- they too have fibres and muscles. Here's a scientific paper investigating the fibres in bat wings. The introduction to the paper describes what the various parts of the bat membrane are and their function in aerodynamics, such as modifying wing shape during flight.

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More generally, the question you are asking is about convergent evolution. A number of taxa have developed controlled flight (insects, pterodactyls, birds and bats).

In vertebrates, the defining point is where they came from (see here for a little comparison): they all used the fore limbs, but pterodactyls used the last bone of the finger, birds the whole series of bones of the limb, while bats used the five fingers. That puts of course structural limitation to how they would look like; but not necessarily what they would be able to achieve.

To answer your specific question, no the bats would not resemble the pterodactyls in structure. But supposing bats met a new environment where they needed more complex wings, it stands to reason they would develop them. The question is: what would this new environment be? Right now, the bats seem quite happy how they are, including in urban areas.

Here starts my speculation: perhaps, if they had to grow bigger for some reason, then it would have to change the mechanics of powered flight (with the principle that if you increase mass, you have to keep up with a stronger engine or you have to become more efficient).

Animals in colder climates would tend to get more massive (Bergman's rule) and more compact (Allen's rule), so as to minimize heat loss. Furthermore, bats hibernate in winter; in case of a glaciation period, bats would not have the opportunity to do so (it would always be cold), so they would have to undergo quite a mutation if they were to survive: they would have to develop a way to retain heat while generating enough surplus energy to power their flight. That would be quite a trick.

Going even further in speculation, a solution for bats would be to become cunning predators, attacking and killing animals with a minimal amount of struggle; since bats would remain gregarious, it would be better if a) those prey animals traveled in herds b) the prey they were very big, providing the bats found an efficient way to kill them, e.g. by causing many bleeding wounds, possibly with a venomous bite or a poisoned claw (imagine a swarm of killer bats attacking a polar bear). Unless they became scavengers.

In any case, the bats might have to change their operation basis, by redeveloping long distance sight (which they are notoriously lacking) as echolocation might become less efficient at large distances and high speeds... unless their preys are really slow or already dead.

Bottom line, a change in their sensory system would probably lead to a corresponding change in their nervous system, and then in the way they handle their wings. We might see refinements of their wings and body structure to achieve feats that the pterodactyls were able to achieve (notably huge size and lifting fairly heavy weights); but structurally they would be different.

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  • $\begingroup$ Where did you get the "dactyl"? $\endgroup$ – JohnWDailey Jun 16 '17 at 12:26
  • $\begingroup$ Good point. I'm not a biologist, but I used it there absent-mindedly it as the original, unscientific name for pterosaurs (for a proper definition, see American Heritage). Perhaps because -dactyl stands for "finger". I am quite willing to correct my answer, if that doesn't come across right. $\endgroup$ – fralau Jun 17 '17 at 6:28

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