
Humboldt’s Squirrel Monkey / Ecuadorian Squirrel Monkey, Sani Lodge, Ecuador
Some taxonomy notes:
Humboldts squirrel monkey (Saimiri cassiquiarensis) used to be considered a subspecies of the Common squirrel monkey (Saimiri sciureus) but has been elevated to full species status.
There's also the Ecuadorian Squirrel Monkey, which is now considered to be a subspecies of the Humboldt's squirrel monkey. Thus the species on the photo is Saimiri cassiquiarensis ssp. macrodon.

Humboldt's squirrel monkey is a species of squirrel monkey from Brazil, Colombia, Ecuador, Peru and Venezuela. It had previously been considered a subspecies of the common squirrel monkey, "S. scuireus", but was elevated to full species status based on a genetic study by Carretero-Pinzón in 2009.