Plica plica Collared Tree Runner
This species was formerly placed in the genus Tropidurus, but I'm glad it was separated out, because (A) these lizards seem very distinct from the other Tropidurus I've seen, and (B) "Plica plica" is really fun to say.
Madre Selva Biological Station, Loreto, PeruJanuary 16, 2013
Collared Tree Runner (Plica plica)
These are very interesting lizards, specialized for a life of running quickly up and down tree trunks. They're basically in this position pretty much all the time, even at night when they're sleeping (as here).

Here is a complete list of the herps I saw in the wild on my 2013 MT Amazon Expeditions trip.

Madre Selva Biological Station, Loreto, PeruJanuary 18, 2013
Collared Tree Runner (Plica plica)
And here's one during the day, simultaneously watching for tasty bugs and also watching for scary photographers.
Santa Cruz Forest Reserve, Loreto, PeruJanuary 21, 2014
Collared Tree Runner (Plica plica)
This colorful young Plica plica was perched on a tree behind the Santa Cruz facility's kitchen. It was willing to hold its pose for me as I slowly crept closer and closer. A few minutes later someone approached a little too quickly and it darted up the tree.

Here is a complete list of the herps I saw in the wild on my 2014 MT Amazon Expeditions trip.

Printed references: