The cranium of C. lomamiensis is similar to that of C. hamlyni in
possessing a distinctive nasal profile (adult males, in particular) that
distinguishes crania in this clade from other Cercopithecus species.
On the basicranium, C. lomamiensis and C. hamlyni both seem to
exhibit distinctive and well-excavated fossae anterior to the
foramen magnum (for longus capitis).
The variably prominent white to cream colored vertical nose
strip shared by C. hamlyni and C. lomamiensis is found in no other
Cercopithecus species. The pelage of both species includes hairs that
are gray at the base with light and dark band pairs moving distally.
The limbs of both species, including the back of the thighs and
perianal region, are black with admixture of gray/silvery hairs.
Males and females of both C. lomamiensis and C. hamlyni have
a prominent facial mane of elongated hairs on the cheeks and
crown, a feature unique to these two species.
The blue perineum, buttocks and scrotum displayed by adult
males are comparable in size and coloration in C. lomamiensis and
C. hamlyni (Fig. 7), and are more extensive than genital patches in
any other Cercopithecus. It is comparable in extent to the buttocks
and genital patch displayed in adult male mandrills (Mandrillus
sphinx).
In both species, the juvenile is pale, uniformly colored and
differs markedly from adults (Fig. 6). The nose stripe is variably
present in juveniles of both species, and is often absent or
indistinct.