Have you ever heard a creationist bring up the "sudden appearance" of bats in the fossil record, and complain about how there are no "transitional" forms between bats and small mammals? Evolutionists usually have to chalk the lack of bat fossils up to the poor preservation of the fragile animals or the incompleteness of the fossil record as a whole. That's beginning to change. Recently a 52 million year old bat fossil was found which lacked the ability to echolocate. The article states that it was probably an "agile climber" due to its long hind limbs. That is another sign that this is a transitional fossil. I can picture a small, mouse-like mammal scurrying up trees, and later evolving skin flaps and long limbs to glide down from the them. We will have to wait and see if fossils like that are found.
For more, see:
How to Make a Bat