Once upon a time I considered becoming an evolutionary bat biologist1. Bats are cool. They’re close to primates on the mammal phylogeny, they have interesting social systems, and some of them have astoundingly sophisticated echolocation systems.
Gareth Jones and Emma Teeling have a paper in TREE: The evolution of echolocation in bats, discussing the phylogenetic history of this trait. It may be quite flexible in the face of ecological constraints and challenges, as there seems to be convergent evolution when different types of calls are mapped onto the molecular phylogenies.
1. Now I just read comics.