Pristimantis malkini Malkin’s Rain Frog
Some other names for this species:
Rio Ampiyacu Robber Frog
Madre Selva Biological Station, Loreto, PeruJanuary 16, 2014
Malkin’s Rain Frog (Pristimantis malkini)
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.

Madre Selva Biological Station, Loreto, PeruFebruary 4, 2016
Malkin’s Rain Frog (Pristimantis malkini)
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:
Printed references: