This seemed like a very distinctive frog, but there are so many frogs in Madagascar that many of them haven't been described yet. The frog in The Authority that this one most closely resembles (at least superficially) is frog photo 5a on page 135, listed under "Platypelis spp. (various unidentified species)". That particular photo is of a frog from Ranomafana, which is not too far from Andasibe, but far enough that it is likely to be a different species. (Note that Platypelis was subsequently synonymized with Cophyla.)

Here is a list of all the reptiles and frogs I saw on this 2023 trip to Madagascar.