Dalponte et al., 2014
Callicebus miltoni, sp. nov.
Type locality: Curva do Cotovelo (08°59’45.21”S, 60°43’42.72”W), region of the mouth of the Pombal stream, Reserva Extrativista Guariba-Roosevelt, right bank of the upper Roosevelt River, municipality of Colniza, Mato Grosso, Brazil.
Holotype: MPEG 42654; Field number JD 550; Skin, skull and complete skeleton; Adult male; Collected by local hunter and then retrieved by J.C. Dalponte at the type locality. December 2010.
Paratypes: MPEG‑42810; Field number FES 04; Adult male; Collected by Felipe Ennes Silva in secondary forest near the confluence of the Guariba and Aripuanã rivers (left bank of the Aripuanã River and right bank of the Guariba River: 07°42’42.10349”S, 60°35’31.47013”W), municipality of Novo Aripuanã, Amazonas, Brazil; January 27, 2013.
MPEG‑42811; Field number FES 05; Adult male; Collected by Felipe Ennes Silva in secondary forest near the confluence of the Guariba and Aripuanã rivers (left bank of the Aripuanã River and right bank of the Guariba River: 07°43’14.05081”S, 60°35’17.78161”W), municipality of Novo Aripuanã, Amazonas, Brazil; January 28, 2013.
MPEG‑42812; Field number FES 06; Adult female; Collected by Felipe Ennes Silva in secondary forest near the confluence of the Guariba and Aripuanã rivers (left bank of the Aripuanã River and right bank of the Guariba River: 07°43’04.16976”S, 60°35’14.70891”W), municipality of Novo Aripuanã, Amazonas, Brazil; January 28, 2013.
MPEG 42991; Field number FES 12; Adult male; Collected by Felipe Ennes Silva and Raimundo Rodrigues da Silva in secondary forest in the left bank of the Aripuanã River, mouth of the Igarapé Jatuarana (07°44’12.24240”S, 60°31’16.16160”W), municipality of Novo Aripuanã, Amazonas, Brazil; August 23, 2013.
MPEG 42992; Field number FES 13; Adult female; Collected by Felipe Ennes Silva and Raimundo Rodrigues da Silva in secondary forest in the left bank of the Aripuanã River, mouth of the Igarapé Jatuarana (07°44’12.24240”S, 60°31’16.16160”W), municipality of Novo Aripuanã, Amazonas, Brazil; August 23, 2013.
MPEG 42993; Field number FES 14; Adult male; Collected by Felipe Ennes Silva and Raimundo Rodrigues da Silva in secondary forest in the left bank of the Aripuanã River, mouth of the Igarapé Jatuarana (07°44’11.17680”S, 60°30’54.83520”W), municipality of Novo Aripuanã, Amazonas, Brazil; August 24, 2013.
Geographic distribution: The records of Callicebus miltoni sp. nov. occurred in the lowlands of the Roosevelt-Aripuanã Depression, an area previously considered by Roosmalen et al. (2002) and Veiga et al. (2008) as part of the distribution of C. cinerascens. The geographic distribution of the new species coincides with the interfluvial region of the Roosevelt and Aripuanã rivers, states of Mato Grosso and Amazonas, Brazil, and these rivers form the western (Roosevelt), eastern (Aripuanã) and northern limits of its distribution. Callicebus miltoni was observed along the right bank of the Roosevelt River, replaced by C. bernhardi which occurs at the left bank of this river (FES, pers. observation). The series of hills resulting from the contact of the Dardanelos plateau and the Roosevelt-Aripuanã Dissected plateau whose declivity acts as an effective terrestrial barrier and represents the southern limit of the distribution of C. miltoni. These formations have abrupt contact with steep ledges, with the Roosevelt-Aripuanã Depression at its north face, and gradual contact with the Parecis plateau and part of the residual plateaus of Madeira-Roosevelt at the south (Brasil, 1980).
Description of the holotype: Dark-ocher (orange-brown) sideburns, withthe individual hairs showing two colored stripes, one basal orange and one distal dark-ocher; forehead with a white (light gray) stripe contrasting with the dark agouti-gray crown; ears colored similarly to crown, but with white (light gray) edges and a discrete white (light gray) tuft; white vibrissae and beige eyelids (in natura); superior part of the body, flanks and external sides of members a uniform gray-agouti, which extends to approximately 1/10th of the tail on the anterior-superior portion; white (light gray) hands and feet, in the same tone of the forehead stripe and ear edges, contrasting with the gray-agouti of the external parts of the members; throat in the same tone as sidesof the face (dark-ocher); chest, belly and internal parts of the members light orange, visibly contrasting with the dark orange of the sideburns and throat; tail (except 1/10th of the anterior-superior portion) uniformly light orange, though the individual hairs show two stripes, one basal light orange and one distal reddish-orange.
Description of the paratypes: The type series of C. miltoni sp. nov., composed of seven specimens, allowed for an initial evaluation of the intraspecific variation in fur color. The observed variation in the paratypes was small, showing the stability of the set of characters that define the chromatic pattern of the species, and the absence of sexual dichromatism. The gray coloration of the crown was lighter in specimens MPEG 42810, 42811, 42812 and 42991, with effects of the distinctness of the forehead stripe. MPEG 42810 showed a very diffuse stripe, almost imperceptible, and specimens MPEG 42811, 42812 and 42991 showed a less contrasting stripe with the crown than that observed in the holotype and in the other paratypes. Specimen MPEG 42993 showed darker sideburns, with a darkened tone, and MPEG 42812 showed lighter sideburns, slightly orange. Specimens MPEG 42811 and 42812 showed a slight brown tone in the gray color of the dorsum, and MPEG 42992 showed this same coloration only in the posterior part of the dorsum (saddle). Specimens MPEG 42812 and 42992 showed a whitish longitudinal stripe in the flanks. Specimen MPEG 42810 showed a more reddish color in the throat, chest and belly, and specimens MPEG 42812, 42991, 42992 and 42993 showed a darker coloration in these regions, less contrasting with that of the throat. Specimen MPEG 42810 had darker hands and feet, less contrasting with the color of the external surface of the members; specimen MPEG 42992 showed less contrasting hands, in addition to brownish fingers, and MPEG 42812 had ankles with brownish extremities. Specimen MPEG 42812 showed a lighter external surface of the members, contrasting with the dorsum, similarly to MPEG 42811 and 42992, but with less intense contrast. MPEG 42991 showed this same pattern only in the anterior members. Specimens MPEG 42812 and 42991 had darker internal surfaces of the members, similar to that of the sideburns; the same was true for MPEG 42992 and 42993, but only in the anterior members. MPEG 42810 had a blackish tone in 2/3 of the proximal portion of the tail (dorsal side), with the ventral side showing a small black portion separating the base from the remaining of the tail. Specimen MPEG 42811 showed some sparse whitish hairs along the tail. Specimens MPEG 42811, 42810 and 42991 had shorter tails, with shorter and less dense hairs and with the coloration of the basal stripe less contrasting with the distal stripe. MPEG 42991 had the basal part of the tail composed by two pairs of small stripes, alternating between golden-yellow and dark brown. MPEG 42992 showed uniformly colored ears, similar to the color of the crown.
Diagnosis: A species of titi monkey belonging to the Callicebus moloch species group, subgenus Callicebus (sensu Groves, 2005). Callicebus miltoni sp. nov. differs from all other Amazonian species of the genus Callicebus by an exclusive combination of characters. It is easily distinguished from species of the same group, particularly those with adjacent distributions, C. bernhardi and C. cinerascens, by the pattern of fur coloration, especially a contrasting gray stripe on the forehead, orange-brown sideburns and throat, dark gray upper torso and flanks, and orange tail (except 1/10th of the dorsal surface at the base of the tail). The tail turned orange-brown after taxidermy in all specimens of the type series, but this remained an exclusive trait of C. miltoni.
Comparisons: Considering the species as a member of the Callicebus moloch species group, C. miltoni differs from its closest geographically neighbor C. bernhardi by the dark-ocher tone of the sides of the face and throat, contrasting with the chest and belly, rather than the brilliant orange of the latter species; by the gray stripe on the forehead contrasting with the darker gray on top of the head, not apparent in C. bernhardi, and by the uniformly gray mid-dorsal region, without the reddish tone of C. bernhardi. Differs from its also closest geographically neighbor C. cinerascens in all characters, including
the uniform gray pattern of the dorsal region, darkocher sides of the face and light gray extremities, rather than the general dark-gray pattern with reddish mid-dorsum and darker extremities of C. cinerascens. Differs from C. moloch by the dark-ocher sides of the face rather than the brilliant orange, and by the uniformly gray mid-dorsum, without the reddish tone of C. moloch. Differs from C. vieirai in all characters, including dark gray agouti forehead with whitish stripe contrasting with the crown (white or white-agouti in C. vieirai); dark ocher (orangebrown) sideburns (white in C. vieirai); ocher neck, orange-brown chest and light ocher (orange) belly (uniformly light yellow to light orange underparts in C. vieirai); and by the uniformly light ocher (orange) tail (agouti with gray base, blackish middle and whitish tip in C. vieirai). Differs from C. baptista by the gray pattern of the dorsum, flanks and external parts of members (dark gray in C. baptista), graywhite member extremities and light-gray stripe of theforehead (both darkened in C. baptista). Differs from C. brunneus in all traits, especially the gray pattern of the dorsum, flanks and external parts of the members (reddish-brown in C. brunneus), gray-white member extremities (darkened in C. brunneus), and light-gray stripe on the forehead (darkened in C. brunneus). Differs especially from C. hoffmannsi by the darkocher sides of the face and orange ventral parts, rather than the uniform yellowish-white of the latter.
Craniometric variables: The type series of C. miltoni is larger than that of other recently described Callicebus species, comprised of seven specimens. Despite this, the number remains low, hindering an analysis of intraspecific variationand interspecific comparisons of craniometric and external measures within the Callicebus moloch species group. Although all specimens are adults, the number of males (5) exceeds that of females (2). External and craniometric variables of the holotype and paratypes are presented in a table.