Certainly a free-tailed bat; need to look at various books such as Mammals of Africa to see if it can safely be narrowed down further...
Thanks! Helpful to know my wife was in the right ballpark.
Wikipedia shows only four free-tailed bat species in Chad:
https://en.wikipedia.org/wiki/List_of_mammals_of_Chad#Order:_Chiroptera_(bats). Gland-tailed, Nigerian, Little, and Midas'.
The only thing that seems fairly certain is that it's not Gland-tailed. The diagram on the bottom right of p. 497 here (
http://www.academia.edu/16901999/Tadarida_bemmeleni_Gland-tailed_free-tailed_bat) shows visible glands to either side of the tail, which is not visible in our tail photo.
Most of the descriptions I could find of Midas' (e.g.,
http://tsammalex.clld.org/parameters/mopsmidas) have it with whitish underparts, which ours did not.
Both Little and Nigerian are dark. We didn't stretch out the wings or flip it over to be able to see the white stripes discussed here (
https://www.researchgate.net/publication/232675210_Chaerephon_nigeriae) that would help confirm.
It may have been a Little. Littles are smaller, and this one was certainly quite small. (Then again, it could have been a juvenile Nigerian.) This site (
http://animaldiversity.org/accounts/Chaerephon_pumilus/) also says that "These bats hunt by themselves and return to their roosts after feeding," which could have explained its solo presence in our shower.
So I'm going to say it was most likely a Little Free-tailed Bat, leaving open the possibility that it might almost as well have been a Nigerian F-t B.
Anybody agree / disagree?