Pristimantis malkini
—
Malkin’s Rain Frog
Also known as:
Rio Ampiyacu Robber Frog

I had no good guess what frog this might be, but Dick Bartlett helpfully pointed out that it looks like Pristimantis malkini, and indeed it does look just like photos of that species that I found subsequently.
Here is a complete list of the herps I saw in the wild on my 2014 MT Amazon Expeditions trip.

Pristimantis malkini has a particularly large head for a frog of this small size, which is evident here.
My Travelogues and Trip Lists page includes a complete list of the herps I saw in the wild on my 2016 MT Amazon Expeditions trip.
Online references:
- Pristimantis malkini account on AmphibiaWeb
- Pristimantis malkini account on Amphibian Species of the World
Printed references:
- Rodríguez, L. O. and Duellman, W. E. 1994. Guide to the Frogs of the Iquitos Region, Amazonian Peru