http://en.wikipedia.org/wiki/Gelada

[ancestor may have been much larger, see theropithecus oswaldii,
gorilla sized, compare it to gigantopith and panda with "extra" thumb
bone for manipulating bamboo.]

Theropithecus, while restricted at present to Ethiopia, is also known
from fossil specimens found in Africa and the Mediterranean into Asia,
including South Africa, Malawi, the Democratic Republic of the Congo,
Tanzania, Uganda, Kenya, Ethiopia, Algeria, Morocco, Spain, and India.

Theropithecus gelada can be physically distinguished from baboons by
the bright patch of skin on its chest. This patch is hourglass-shaped,
and on males, bright red and surrounded by white hair. On females the
patch is far less pronounced. However, when in oestrus, the female's
patch will brighten, and a "necklace" of fluid-filled blisters forms
on the patch. This is thought to be analogous to the swollen buttocks
common to most baboons experiencing oestrus. This modification likely
came about due to the Gelada's unique mode of feeding - it spends most
of its waking hours grazing from an upright sitting position, rump
hidden beneath and so unavailable for display. The male Gelada's tail
is about as long as the body and densely tufted at the tip; it also
has a long and flowing mantle and mane.

[compare to sitting gorillas in water, bare chest but elsewhere
haired, loss of tail due to both sitting habit in shallow water and
laryngeal air sacs for both flotation and vocalization. also compare
chest estral color in female to scent sternal pit of siamang and
orangutan.]

The Gelada is exclusively herbivorous but is specialised as a
grass-eater, consuming every part of the plant (but favouring one part
over the others depending upon season), from green blades (in the wet
season) to seeds to rhizomes (in the dry season) to stalks, flowers,
and fruits. It has the most opposable thumb of any of the catarrhine
primates (not including humans), allowing it to pick apart grasses
with great dexterity to select the most nourishing meal. It is one of
the only true grazing monkeys.[7]

[this fits with C4 consumption in ancient hominids, and Falasha's
papyrus idea.]

Hunting and habitat destruction have forced the Gelada into areas
formerly inhabited only by the Olive Baboon, and hybridisation between
the two species has been observed.

[Note large canines, lack of paranasal sinuses, no air sac. not a
wetlands feeder.]

http://blogs.scienceforums.net/evoanthro/2008/02/09/meet-an-ancestor-theropithec\
us-oswaldi/
T oswaldii was at gallery forests, compatriot to H ergaster and
apiths. Replaced by baboons, perhaps during climate changes.