Roosmalen et al., 2002
Type locality: Unknown. Holotype said to be caught somewhere along the middle to upper Rio Purús together with the paratypes. The holotype is an adult female, entire animal preserved in alcohol, Mammal Collection of the National Institute for Amazon Research, INPA no. 4030, alive weighing 725 g, brought to M.G.M. van Roosmalen by fishermen on June 20, 2000. Paratypes: Four individuals, brought to M.G.M. van Roosmalen by fishermen, said to be caught along the middle or upper Rio Purús.
Distribution: Since the new species seems to be phenotypically most closely related to both C. caligatus and C. dubius, we assume Callicebus stephennashi should occur along the right bank of the Rio Purús in between the distributions of C. caligatus and C. dubius. As a possible distribution, we suggest the interfluve delineated by the Rios Purús/Ipixuna/Madeira/Mucuím.
Description: Forehead, superciliary vibrissae, and anterior portion of crown black, sharply contrasting with posterior portion of crown, nape, dorsum and rump which are silvery or buffy mixed with brownish agouti or brownish-black; ears blackish; lower arms and legs bright red, sometimes dark red as in C. caligatus and C. baptista, like sideburns, under parts, and inner sides of limbs, contrasting with silvery or buffy mixed with brownish agouti upper and outer parts; upper surface of cheiridia silvery buffy to white, the proximal third of foot red like lower legs, the hands entirely silvery or white; proximal portion of tail silvery mixed with brownish agouti to blackish brown, then black mixed with white or buffy, and distal half to two-third entirely white or buffy. Distinguished from C. caligatus by black superciliary vibrissae, forehead and anterior portion of crown sharply contrasting with silvery agouti remainder of crown, nape and upper parts of body, by bright red instead of dark red-brown lower arms and legs, by white or buffy instead of blackish cheiridia, and almost entirely white or buffy tail; from C. dubius by black forehead and anterior portion of crown, lacking a white blaze, by white or buffy cheiridia instead of white digits only, and almost entirely white or buffy tail; from C. cupreus by black frontal blaze contrasting sharply against a silvery crown and nape, almost entirely white or buffy tail instead of an overall dark tail with white pencil, and by white or buffy instead of brown agouti cheiridia; from C. brunneus by its bright red sideburns, lower arms and legs, and under parts, white or buffy cheiridia, and silvery agouti to silvery brown upper parts and sides of body.
Measurements: See publication at http://www.primate-sg.org/PDF/NP10.S.pdf
Description of holotype: Black of forehead and superciliary vibrissae continuing over anterior portion of crown as in C. caligatus, but sharply contrasting with posterior portion of crown, nape, back and rump which are buffy to silvery mixed with brownish agouti, the lax hairs cresting against shorter black hairs in front and longer raised nuchal hairs behind; ears blackish; hairs of dorsum and sides of body silvery mixed with brownish agouti, the individual hairs 4 cm long, six-banded as follows: proximal 1.5 cm brownish agouti to black-brown, then 3 white or silvery bands each alternating with a brown or blackish band, the tip of each hair silvery; lower arms and legs uniformly bright red like sideburns, sides of head, beard, under parts, and inner sides of limbs, contrasting with upper arms and thighs which are buffy to silvery mixed with brownish agouti; upper surface of cheiridia silvery white to buffy, the proximal (ankle) part of foot (3 cm) red like lower legs, the remaining 6 cm silvery white to buffy, upper surface of entire hands including wrists silvery or white; basal (proximal) one-sixth (ca. 8 cm) of tail same colour as lower back and rump, next one-sixth (ca. 8 cm) black mixed with white or buffy (black hairs with 1 cm long white tip), remainder two-third entirely white or buffy; hairs of sideburns, throat, chest, belly, and inner side of limbs not banded red; blackish face naked except for fine buffy hairs surrounding lips and between nostrils.
van Roosmalen, G.M.; van Roosmalen, T. and Mittermeier, R.A. (2002). A taxonomic review of the titi monkeys, genus Callicebus Thomas 1903, with the description of two new species, Callicebus bernhardi and Callicebus stephennashi, from Brazilian Amazonia. Neotropical Primates 10(Suppl.): 1-52.
Röhe and Silva Jr., 2003
Distribution: During our survey, we did not observe Callicebus stephennashi, confirming its restriction to the area between the left bank of the Rio Ipixuna and the right bank of the Rio Mucuim.
Localities: AM Interfluvio R. Ipixuna e Mucuim no Purus (06°30’S 64°00’W); AM médio e alto rio Purus (05°30’S 63°00’W).
Auricchio, P. (2010). A morphological analysis of some species of Callicebus. Neotropical Primates 17(2): 47-58.