Athena Review Vol. 5, no. 1
Records of Life: Fossils as Original Sources
38. Old World Monkeys: Miocene and Pliocene
Miocene Cercopithecoids
Victoriapithecus
Victoriapithecus macinnesi was a Middle Miocene Old World Monkey (Cercopithecoid) known from a single fossil of a male skull found near Lake Victoria in Kenya by Brenda Benefit (fig.1). This is the earliest Old World Monkey fossil found to date. It is closely related to the extinct Prohylobates species.
The
postcranial remains of V. macinnesi indicate had an average body mass
of around 7 kg (15 lb) and that it was quadrepedal (i.e., walked on all
fours). On the forelimbs, the distal end of the humerus shows a narrow
articulation and a deep ulnar notch. Victoriapithecus shares various craniofacial features with the Oligocene
catarrhine Aegyptopithecus zeuxis and early Miocene hominoid Afropithecus turkanensis. One of the strongest points of similarity is the structure of the frontal bone, part of a primitive trait complex related to small brain size, which is also observable in Aegyptopithecus (Simons et al. 2007). Based on the single known skull fossil, the volume of the Victoriapithecus brain was 36 cm3.
Fig.1: Skull of Victoriapithecus macinessi (Mus.Nat.Hist.Paris, cast)
Victoriapithecus has a moderately long, muzzle and midfacial region, a long and forward- tapering premaxilla, broad upper central incisors with long roots, and a deep cheek region relative to facial height (Benefit and McCrossin 1991) . It had a dental formula of 2:1:2:3 on both the upper and lower jaws. Its lower molars are bilophodont with low cusps. The canines show sexual dimorphism, with a large upper left canine in the extant male fossil skull.
Mesopithecus
Mesopithecus ("middle monkey") was a Late Miocene Old World monkey (Cercopithecoid) living in Europe and western Asia 7-5 mya. Once considered a possible ancestor of the grey langur, a more recent study by Pan et al.
(2004)
suggests that they are more closely related to the snub-nosed monkeys
and doucs.Mesopithecus pentelicus had a body length of about 40 cm (16 in), with considerable sexual dimorphism beween males and females in body and skull sizes (fig.2). It had a slender body with long, muscular limbs and flexible fingers, and was well adapted to both walking and climbing. Its teeth suggest that it primarily ate soft leaves and fruit. It is thought to have resembled a modern macaque or colubine monkey.
Fig.2: Male and female skulls of Mesopithecus pentelicus (Mus.Capellini Bologna, casts)
Pliopapio
Pliopapio ("pliocene baboon") was an early baboon from the Late Miocene to Early Pliocene whose fossils were discovered in the Afar region of Ethiopia. The type species, Pliopapio alemui, was discovered among a group of fossils at Aramis in the Middle Awash Valley, dated by argon/argon to 4.4 mya. It has also been found at Gona from the same time frame. Earlier fossils found subsequently in the Middle Awash region date to 5.3 mya, pushing the date range of this taxa back into the Late Miocene (Frost 2001).
Pliopapio resembles other members of the Papionini, a tibe of monkeys which includes the macaques of North
Africa and Asia, as well as the baboons, geladas, mangabeys, kipunji,
drills, and mandrills, which are essentially from sub-Saharan Africa. In size Pliopapio was similar to the larger macaques and smaller baboons. Its teeth are similar to most papionin monkeys, but the molar teeth are somewhat narrower and taller. Its molar surfaces showed microwear consistent with a diet of fruits and or
leaves, and especially softer food items.Fig.3: Skull of Pliopapio alemui (after Frost 2001).
Based on dentition, the male body weight of Pliopapio averaged 12 kg., and female body wight 8.5 kg., showing a degree of sexual dimorphism. Pliopapio possessed an elongated, narrow muzzle, and lacked sagittal or nuchal crests. The few known limb fragment indicate it was a semi-terrestrial quadrupedal monkey, more adapted to arboreal locomotion than baboons, but less than mangabeys.
Theropithecus
Theropithecus brumpti ("wild beast ape") was a Pliocene baboon-like monkey who lived in the Omo Valley of Ethiopia 3 million years ago. Their descendents are the gelada (Theropithecus gelada), who live today in the high grasslands of Ethiopia. Both T. brumpti and T. gelada belong to the Papionini, and are related to the baboon.
Theropithecus brumpti was a quadripedal, ground- dwelling monkey
who lived in riverine forest habitats, and ate grass and other ground- level vegetation. Their molars had
unusually high crowns with complex surfaces which allowed them to chew
nuts as well as tough plant fibers with silica content and grit. T. brumpti had dexterous, manipulative hands. Males
grew very large, up to 45 kilograms. in weight, compared to modern male
geladas whose weight averages around 20 kilograms. The species
displayed a high degree of sexual dimorphism in size and dentition.
Like most papionins, the male possessed large canine teeth. Their skulls (fig.4) are
notable for forward-protruding cheekbones. Fig.4: Skull of Theropithecus brumpti, frontal and side views (American Museum of Natural History cast; photo: Athena Review).
Theropthecus brumpti fossils are mostly known from skulls and mandibles found in Pliocene deposits excavated in the Shungura Formation, at the Omo River, Ethiopia. This specimen was recovered by N. Boaz in 1973.
Paracolobus
Paracolobus ("near colobus") is a Cercopithecoid or Old World Monkey from Kenya in East Africa, dating from the Late Miocene and Pliocene periods
(6-3 mya). It is considered an ancestor of today`s colobine
monkeys. Paracolobus was one of largest colobine (leaf-eating) monkeys ever known. Like the present-day proboscis monkeys, Paracolobus lived mainly in trees.
Fig.5: Skull of Paracolobus chemeroni (Yale Peabody Museum cast; photo: Athena Review).
The fossil skull of Paracolobus chemeroni (fig.5) was discovered by Richard Leakey and his co-workers at Lake Turkana, Kenya in 1969. The fossil skeleton (fig 6; AMNH 129319) was discovered in the Baringo Basin of Kenya in 1966 by W.W. Bishop. Dating from three million years ago, most of the skeleton is present, with only parts of the hands, feet, ribs, and skull missing.
More recently, Hlusko (2007) has reported an earlier, Late Miocene species of Paracolobus from Lemudong'o, Kenya dating from about 6 mya. Finds include at least three species of colobine. Based on paleoecological reconstruction and the postcranial morphology of the fossils, colobines in this area of Africa were then occupying a relatively closed or forested habitat, and were a primarily an arboreal group
Fig.6: Skeleton of Paracolobus chemeroni (American Museum of Natural History cast; photo: Athena Review).
Cercopithecoides
Cercopithecoides is a genus of medium to very large extinct colobine monkeys from the Late Pliocene to Early Pleistocene period. Four known species vary in size, with the two largest being C. kimeui and C. williamsi (Frost and Delson, 2002). C. williamsi is known from multiple sites in East and South Africa (Freedman and Brain 1972; Leakey 1982; Jablonski 2002). These fossil specimens are dated in the range of 3.0-1.5 mya.
Unlike extant arboreal colobines, the extinct colobines are similar in their postcranial skeltons to more terrestrial cercopithecoids (Leakey et al., 2003). Evidence for sexual dimorphism consists of the presence of a longer, narrower cranium, a larger canine, and a larger P3 in presumed males. The cranium of C. williamsi is similar to that of modern colobines in possessing the wide face, wide interorbital space, and large orbits, but the mandible differs in being shallow with an obliquely oriented ramus.
Two specimens of C. williamsi now at the University of the Witwatersrand (fig.7) include MP113 from the Makapansgat Limeworks and BF42 from Bolt’s Farm (Freedman 1965). BF42 is a nearly complete female cranium including the maxillary dentition. MP113 includes an intact male facial skeleton encompassing the anterior cranial vault and complete maxillary alveoli.
Fig.7: Skulls of two Late Pliocene Cercopithecoides williamsi colobine monkeys, including A) the male skull MP113, and B) the female skull BF42 (after Kuykendall and Rae 2008, fig.1).
Kuykendall and Rae (2008) analyzed the two skulls and their retention of maxillary sinuses. These hollows or sacs in the facial bones on either side of the nasal openings represent an anatomical character that is absent in modern colobine monkeys, and also absent in all modern cercopithecoids except macaques. The trait is also absent in the Middle Miocene cerapithecoid Victoriapithecus (Benefit and McCrossin 1993). Presence of this trait in C. williamsi, meanwhile, shows a more complex evolutionary history, indicating that the possession of maxillary sinuses has both disappeared, and re-emerged several times in the history of Old World monkeys through convergence or homeoplasy.
References:
Benefit, B.R. and M.L. McCrossin 1991. Ancestral facial morphology of Old World higher primates. Proc. Natl. Acad. Sci. 88 (12): 5267–71.
Benefit, B.R. and M.L. McCrossin 1993. Facial anatomy of Victoriapithecus and its relevance to the ancestral cranial morphology of Old World monkeys and apes. Am J Phys Anthropol 92:329–370.
Freedman L. 1965. Fossil and subfossil primates from the limestone deposits at Taung, Bolt’s Farm and Witkrans, South Africa. Palaeontol Afr 9:19–48.
Freedman L and C.K. Brain 1972. Fossil cercopithecoid remains from the Kromdraai australopithecine site (Mammalia: Primates). Ann Trans Mus 28:1–16.
Frost, S. 2001. New Early Pliocene Cercopithecidae (Mammalia: Primates) from Aramis, Middle Awash Valley, Ethiopia . American Museum Novitates. 3350: 1–36
Frost S and E. Delson 2002. Fossil Cercopithecidae from the Hadar formation and surrounding areas, Pliocene of Ethiopia. J Hum Evol. 43:687–748
Hlusko, L.J. 2007. A new Late Miocene species of Paracolobus and other cercopithecidae (Mammalia: Primates) fossil from Lemudong'o. Kenya. Kirtlandia, Cleveland Mus. Nat Hist.
Jablonski N.G. 2002. Fossil Old World monkeys: the Late Neogene radiation. In: Hartwig WC, editor. The primate fossil record. Cambridge: Cambridge Universtiy Press. p255–299.
Kuykendall, K.L. and T.C Rae 2008. Presence of the Maxillary Sinus in Fossil Colobinae (Cercopithecoides williamsi) from South . Anatomical Record 291:1499–1505.
Leakey M.G.1982. Extinct large colobines from the Plio-Pleistocene of Africa. Am J Phys Anthropol 58:153–172.
Leakey M.G., M.F.Teaford, and C.V. Ward 2003. Cercopithecidae from Lothagam. In: Leakey MG, Harris JM, editors. Lothagam: the dawn of humanity in Africa. New York: Columbia University Press. pp 201–248.
Pan, Ruliang; C. Groves,and C. Oxnard 2004. Relationships Between the Fossil Colobine Mesopithecus pentelicus and Extant Cercopithecoids, Based on Dental Metrics. American Journal of Primatology. 62 (4): 287–299.
Simons, E.L., E.R. Seiffert, T.M. Ryan, and Y.Attia 2007. A remarkable female cranium of the early Oligocene anthropoid Aegyptopithecus zeuxis (Catarrhini, Propliopithecidae). Proc.Nat.Acad.Sci. 104, no. 21, pp.8731-8736
Glossary