3.3.3.2 Alouatta discolor (von Spix, 1823) Type: Juvenile male, Munich Museum. Type locality: Forte Curupá (= Gurupá), south margin of Rio Amazonas, between Rio Tapajós and Rio Xingu, state of Pará, Brazil. [Not the Island of Gurupá]. Common name: Spix’s red-handed howler monkey. This species is distributed from the right bank of the rios Tapajós and Juruena to the rios Xingú and Irirí (Gregorin 2006; Glander and Pinto 2013) (Fig. 3.1). Elliot (1913) regarded this taxon as a synonym of A. belzebul given that he considered that the type (a juvenile with a darker pelage) presented pelage coloration within the range of this species. Lönnberg (1941) described a new subspecies of A. belzebul to the east of the Rio Tapajós, naming it A. b. tapajozensis, but Cruz Lima (1945) argued that Lönnberg’s tapajozensis was a synonym of Spix’s discolor. He included this form as a subspecies of A. belzebul (A. b. discolor). Later authors (e.g., Cabrera 1957; Hill 1962) followed Cruz Lima in recognizing the form discolor as a subspecies of A. belzebul. Groves (2001, 2005) considered discolor as a synonym of a monotypic A. belzebul, but Gregorin (2006), after a detailed analysis of morphometric data and pelage coloration patterns of over 70 individuals from Pará, concluded that the diagnostic characters of the hyoid bone and pelage coloration clearly distinguish A. discolor from the other two phylogenetically close taxa (A. belzebul and A. ululata) and are sufficiently trustworthy to validate its specific status. To date, there are no genetic data from individuals of this region, so we only tentatively consider A. discolor as a full species following Gregorin (2006).

Published as part of Cortés-Ortiz, Liliana, Rylands, Anthony B. & Mittermeier, Russell A., 2015, Howlec MonSeys Adaptive Radiation, Systematics, and Mocphology, pp. 49-84 in The Taxonomy of Howler Monkeys: Integrating Old and New Knowledge from Morphological and Genetic Studies, New York Heidelberg Dordrecht London :Springer on page 72, DOI: 10.1007/978-1-4939-1957-4, http://zenodo.org/record/17352914