The Urubamba brown titi monkey, Callicebus urubambensis
The Urubamba brown titi monkey (Callicebus urubambensis) was described in 2015 by Vermeer and Tello-Alvarado, based on observations in the wild, the collection of a holotype and museum specimens. Specimens of Peruvian brown titi monkeys, collected in 1927 near the Río Urubamba and present in the collection of the American Natural History Museum (New York) were identified by Hershkovitz as C. brunneus. However, the additional research by Vermeer and Tello-Alvarado revealed that the Urubamba brown titi monkey differs from the Brazilian brown titi monkey and is a valid species.
The species is restricted to the western (left) side of the Río Urubamba and the Manu National Park, Peru.