In this monograph, was studied non-geographic and geographic variation of taxa of Howling Monkeys, genus Alouatta Lacépède, 1799, occuring in Brazil, in order to solve the taxonomy of the group. For the morphological analysis, were examined a total of 1,286 specimens kept in five Brazilian and two North-American museums. The material consisted mostly of skin, skull and hyoid bone; skeleton or fluid-preserved specimens were scarse. The study was based on qualitative analysis of the morphological complexes in addition 18 morphometric characters of the skull and hyoid bone. Prior to making taxonomic decisions, was conducted a study of geographic, sexual, ontogenetic, and individual variation. Were recognized ten species of Alouatta occuring in Brazil and most of them were defined by discrete, but diagnostic characters. The species are: Alouatta caraya (Humboldt, 1812), A. fusca (Geoffroy Saint-Hilaire, 1812), A. clamitans Cabrera, 1940, A. belzebul (Linnaeus, 1766), A. discolor (Spix, 1823), A. ululata Elliot, 1912; A. juara (Linnaeus, 1766), A. macconnelli (Humboldt, 1812), A. puruensis Lönnberg, 1941, and A. nigerrima Lönnberg, 1941. Alouatta macconnelli and A. clamitans showed noticeable geographic variation on pelage coloration and some morphometric characters (polymorphism) difficulting their definition and geographic limits. Alouatta belzebul presented an accentuated geographic mosaic variation on coat coloration. Alouatta ululata and A. puruensis were defined in presenting sexual dicromism on pelage, but this character can be an artefate due the small sample and both taxa need further studies to confirm their validity. Alouatta belzebul mexianae Hagmann, 1908 was sinonimized with A. discolor; and the validity of Alouatta seniculus amazonica Lönnberg 1941 was not considered.
Brazilian species; howling monkeys; morphology; taxonomic revision; variation
