Twan Leenders, biologist and author of the Guide to the Amphibians and Reptiles of Costa Rica (and some other books on reptiles and amphibians in Costa Rica), helped me identifying this species.
I met Twan during my visit at the Biological Station Rara Avis (now an Eco Lodge) in the Braulio Carrillo National Park in Costa Rica in 2003, where he showed me this rather rare species that he found that morning in the rainforest.
This species is sometimes also called Berthold's Bush Anole.

Rara Avis, Braulio Carrillo National Park, Costa Rica, March 2003