The Distribution and Taxonomy of Titi Monkeys (<i>Callicebus</i>) in Central and Southern Peru, with the Description of a New Species

Here we report on the results of a study on the distribution and taxonomy of titi monkeys, genus Callicebus, in the central part of Peru. We reinstate Callicebus toppini Thomas, a species described in 1914, but since then neglected by science. It evidently has a wide distribution in southern Peru, western Brazil and northern Bolivia. Based on field observations, analysis of museum specimens, and photographs, we also describe a new species of Callicebus from the Río Urubamba basin, endemic to Peru. Reliable identification of titi monkeys observed in the wild is crucial to avoid confusion and to determine conservation strategies.