Alouatta nigerrima Lönnberg, 1941

3.3.4.8 Alouatta nigerrima Lönnberg, 1941 View in CoL

Type: Originally in the Stockholm Museum (none of the seven specimens was designated as holotype in the original description [ da Cruz Lima 1945]). Lectotype in the Swedish Museum of Natural History NRM A63 3316 (indicated by Cabrera [1957], and officially designated by Gregorin [2006]).

Type locality: The left margin of the Rio Tapajós (restricted by Cabrera [1957] to Patinga, state of Pará, Brazil).

Common name: Amazonian black howler.

Alouatta nigerrima is endemic to Brazil, with a geographic range that extends between the rios Madeira and Tapajós, north to the Rio Amazonas ( Fig. 3.1 View Fig ). A few specimens have also been collected in the northern margin of the Rio Amazonas, in the regions of Oriximiná and Obidos, in the state of Pará ( Gregorin 2006).

Lönnberg (1941) described A. nigerrima as a full species, distinct from its neighbor A. belzebul tapajoensis (here A. discolor , see above), and considered that these two forms were phylogenetically close. One of the most important distinctive characters described by Lönnberg (1941) as diagnostic of A. nigerrima is related to the morphology of the hyoid bone, which clearly distinguishes it from A. discolor ( Gregorin 2006) . Cruz Lima (1945) also considered A. nigerrima to be a distinct species, but Hershkovitz (1949) placed it as a subspecies of A. belzebul (although recognizing that the morphology of the hyoid bone could place it closer to A. seniculus than to A. belzebul ). Cabrera (1957) and Hill (1962) followed Hershkovitz in listing nigerrima as a subspecies of A. belzebul .

Armada et al. (1987) studied the karyotypes of 10 A. belzebul individuals captured on the left margin of the Rio Tocantins, state of Pará, Brazil, and of one captive individual of unknown origin tentatively identified as A. belzebul nigerrima , based on pelage coloration. They found considerable differences in the karyotypes of these two forms, and suggested a taxonomic reevaluation of these taxa. Oliveira (1996) noted that the g-banding pattern of A. b. nigerrima presented by Armada et al. (1987) was more similar to the one observed in A. seniculus than in A. b. belzebul . Bonvicino et al. (2001) analyzed mitochondrial sequence data of seven Brazilian Alouatta species, including a sample from the same individual identified as A. belzebul nigerrima by Armada et al. (1987), and found that it was phylogenetically closer to A. macconnelli and A. seniculus than to A. belzebul .

Gregorin (2006) analyzed the pelage coloration and cranial morphology of 98 specimens of nigerrima , and found that the distinctive black pelage was invariable across most of the specimens he analyzed. He also noticed that the morphology of the hyoid bone was distinct from any other Brazilian howler (confirming the observations previously made by Cruz Lima [1945]), but that it is more similar to the hyoid of A. macconnelli than to that of A. belzebul .

These morphological and genetic studies have supported the early recognition of A. nigerrima as a distinct species from A. belzebul and phylogenetically closer to the seniculus group. The genetic analyses have, however, been based on a single individual of unknown origin. Given its proximity to A. macconnelli and the fact that this latter taxon presents great variation in pelage coloration that includes individuals that are completely black (see Gregorin 2006), the question arises as to whether this specimen really originates from the range of A. nigerrima or is in fact a dark phase individual of A. macconnelli . Further genetic studies from individuals of known origin are needed to discard this possibility and validate the status of A. nigerrima .