Re: I'm having trouble finding info on the coevolution of bats

I don't quite understand your question here. 

My first problem is your use of the term "coevolution." Coevolution usually 
refers to correlated changes within two ecologically related species, such 
as predator and prey or host and parasite. You seem to be using the term to 
refer to two aspects of the same of the same creature. Most evolutionary 
scientists prefer to examine the "total morphological pattern," which means 
that you wouldn't examine just one aspect of an animal without considering 
its interactions with all its other parts.

You seem to be asking about the relationship between flight and 
stereoscopic vision. I too can only give you opinion, but I can tell you 
that stereoscopic vision seems to be an important part of arboreal 
(tree-living) existence. To me, that would suggest that vision came first, 
flight came second.

Some resources you might want to check:

Romer, AS (1966) Vertebrate Paleontology. 3rd edition. University of 
Chicago Press: Chicago.

Carroll, RL (1988) Vertebrate Paleontology and Evolution. WH Freeman and 
Company: New York.