PBS Eons has a new episode about bats.  Bats are very rare in the fossil record and thus we still have much to learn about their evolutionary history.  What came first flight or echo-location?

Bats pretty much appear in the fossil record as recognizable, full-on, flying bats. And they show up on all of the continents, except Antarctica, around the same time. So where did bats come from? And which of the many weird features that bats have, showed up first?