Byrne, HazelRylands, Anthony BCarneiro, Jeferson CAlfaro, Jessica W LBertuol, Fabricioda Silva, Maria N FMessias, MariluceGroves, Colin PMittermeier, Russell AFarias, IzeniHrbek, TomasSchneider, HoracioSampaio, IracildaBoubli, Jean P.2016-03-012016-03-011742-9994http://dx.doi.org/10.1186/s12983-016-0142-4http://hdl.handle.net/1885/99882Background Titi monkeys, Callicebus, comprise the most species-rich primate genus—34 species are currently recognised, five of them described since 2005. The lack of molecular data for titi monkeys has meant that little is known of their phylogenetic relationships and divergence times. To clarify their evolutionary history, we assembled a large molecular dataset by sequencing 20 nuclear and two mitochondrial loci for 15 species, including representatives from all recognised species groups. Phylogenetic relationships were inferred using concatenated maximum likelihood and Bayesian analyses, allowing us to evaluate the current taxonomic hypothesis for the genus. Results Our results show four distinct Callicebus clades, for the most part concordant with the currently recognised morphological species-groups—the torquatus group, the personatus group, the donacophilus group, and the moloch group. The cupreus and moloch groups are not monophyletic, and all species of the formerly recognized cupreus group are reassigned to the moloch group. Two of the major divergence events are dated to the Miocene. The torquatus group, the oldest radiation, diverged c. 11 Ma; and the Atlantic forest personatus group split from the ancestor of all donacophilus and moloch species at 9–8 Ma. There is little molecular evidence for the separation of Callicebus caligatus and C. dubius, and we suggest that C. dubius should be considered a junior synonym of a polymorphic C. caligatus. Conclusions Considering molecular, morphological and biogeographic evidence, we propose a new genus level taxonomy for titi monkeys: Cheracebus n. gen. in the Orinoco, Negro and upper Amazon basins (torquatus group), Callicebus Thomas, 1903, in the Atlantic Forest (personatus group), and Plecturocebus n. gen. in the Amazon basin and Chaco region (donacophilus and moloch groups).Surveys were funded by the Sustainable Development of the Brazilian Biodiversity Program – PROBIO / MMA / BIRD / GEF / CNPq, the Zoological Society of San Diego, University of Auckland and National Geographic Waitts grants and a CAPES/FAPEAM grant to JPB. Molecular analyses and six field expeditions were funded in part by FAPEAM/SISBIOTA and CNPq SISBIOTA Program (No. 563348/2010-0) to IF. Funding for this research was also provided by CNPQ (Grants 306233/2009-6 to IS and 305645/2009 to HS) and grants from CAPES AUXPE 3261/2013 Pro-Amazônia project 047/2012 to IS, HS and IF.26 pages© 2016 Byrne et al. Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.CallicebinaeTiti monkeyGenus-level taxonomyMolecular phylogeneticsPlatyrrhiniCallicebusCheracebusPlecturocebusAmazonAtlantic forestenByrne et al.2016-03-0110.1186/s12983-016-0142-42018-11-29