The average body mass for both the male and female dusky titi is about 1 kilogram. The canines are sexually monomorphic for this species (Kinzey, 1972). The tail of this New World species is non-prehensile (Hershkovitz, 1988). The dental formula for this species is 2:1:3:3 on both the upper and lower jaws (Ankel-Simons, 2000). This species has a pelage coloration that is buffy or grayish agouti to pale brown agouti on the dorsal side of the head, trunk, and limbs (Hershkovitz, 1990). The ventral side, inner side of the limbs, and the sideburns of the face are orange in color (Hershkovitz, 1990). The tail is colored blackish agouti terminally and orange or buffy basally (Hershkovitz, 1990).
The dusky titi is found in the country of Brazil in the states of Para, Mato Grosso, and parts of Amazonas and Rondonia (Hershkovitz, 1990). In the state of Para this species is found from the west bank of the Tocantins-Araguaia River west to the east bank of the Tapajos River, and south to the headwaters of the Araguaia, Xingu, and Tapajos in the state of Mato Grosso (Hershkovitz, 1990). The range of the dusky titi also extends to the Jiparana and Madeira Rivers (Ferrari and Lopes, 1992). This species lives in forests in swamps and allow river and lake edges in the lower canopy (Kinzey, 1981).
The dusky titi is primarily a frugivorous species, but also eats leaves and insects. The dusky titi has also been known to eat bamboo shoots (Fleagle, 1988). This species feeds in small groups, and groups will feed on the same food at the same time (Kinzey, 1981). The dusky titi begins feeding in the early morning before taking about an hour rest during mid-day (Kinzey, 1981). This species is diurnal and arboreal and rarely comes to the forest floor (Kinzey, 1997).
The dusky titi moves through the understory of the forest quadrupedally as well as by leaping (Fleagle, 1988). This species often uses vertical clinging when feeding (Fleagle, 1988). This species moves on the upper surfaces of supports (Kinzey, 1981).
The dusky titi has a monogamous mating system. Once mated an individual prefers his/her mate over other conspecifics of the opposite sex (Anzenberger, 1986, 1988). The basic group is composed of the breeding pair and their offspring. Grooming is an important activity that serves to strengthen social bonds amongst members of the group. The males participate in caring for the infants. Males will carry the infants, and their role as carrier increases after the first few weeks (Welker et al., 1981). Food sharing with the young after they are finished nursing occurs in the dusky titi for the first year of life of the young (Garber and Leigh, 1997). This species, like members of its genus, are highly territorial (Kinzey, 1997). Pairs of dusky titis have been know to engage in duets with other pairs at dawn (Fleagle, 1988).
tail-entwining: This is used to reinforce bonds amongst pairs. This is where two individuals are sitting and their tails are wrapped around each others.
social grooming: This is when one individual will remove dead skin and parasites from another individual. This is an important behavior for the dusky titi, occurring frequently throughout the day (Kinzey, 1981). This is common between adult males and females, and the young will groom adults and vice versa (Kinzey, 1981).
The dusky titi gives birth to a single offspring. The gestation length for this species is 160 days (Garber and Leigh, 1997). The interbirth interval for this species is about one year (Garber and Leigh, 1997). The birth season for this species is between November and March (Kinzey, 1981). Young are weaned from their mothers at 8 months of age (Garber and Leigh, 1997).