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MONKEYS
ANTHROPOID PRIMATES
monkey
monkey

     The earliest group of anthropoid primates are the Oligopithecines known from the Late Eocene which include Oligopithecus savagei, Catopithecus browni, and Proteopithecus sylviae.  Fossils of teeth are similar to those primates which feed on insects and fruit.  The large separation between the orbits (the interorbital distance) is similar to that of prosimians which rely more on their sense of smell than the smaller distance observed in all other anthropoids.  Although the braincase of Catopithecus was crushed, it appears that its brain size tobody size ratio was smaller than modern anthropoids (Rasmussen, 1992).  The incomplete fossil of Algeripithecus suggests that simians existed in North Africa by the early to mid Eocene and the eleven known simian genera of the Fayum deposit in Egypt (including Catopithecus ) date from the boundary between the Eocene and Oligocene.  One of the Fayum simians, Plesiopithecus, may have lacked incisors in the lower jaw (Martin, 1993).

CATOPITHECUS

     Catopithecus browni was an Upper Eocene primate which may be near the base of the anthropoid tree.  Catopithecus was a small monkey outwardly similar to a marmoset. It possessed forward facing eyes, bifocal vision, a larger brain, and a monkey-like face (Kingdon, 2003). A number of specimens have been found including a virtually complete skeleton.  Catopithecus possesses several prosimian characteristics but is thought to be near the base of the anthropoids.  Its upper central incisors are larger than the lateral incisors as in anthropoid primates.

Although the lower central incisors are smaller than the lateral incisors (this is an adapid characteristic; see illustration below); the incisors are similar to those of anthropoids rather than prosimians (such as Arsinea) (Simons, 1995; Culotta, 1995).

teeth

     In Catopithecus, there was sexual dimorphism in the canine structure, a trait which is unknown in prosimians.  Unlike most other Eocene primates, the roots of the central upper incisors fit closely like those of the anthropoids.  In Catopithecus, there is the first appearance of anthropoid-like suture in the lower jaw.  The postorbital closure of the eye region is equivalent to that of the anthropoid Aegyptopithecus and is not found in prosimians.  This protects the eye and relieves the stress from chewing.  The ectotympanic circles of the auditory opening are similar to Aegyptopithecus (and some prosimians).  The foramen magnum and carotid foramen are similar to those found in higher primates.  Catopithecus seems to be related to Proteopithecus and later Oligopithecus which are anthropoids.

monkey

     It is possible that higher primates evolved in Asia.  Eosimias sinensis, Eosimas centennicus have been classified as higher primates and it is possible that Pondaungia coutteri and Amphipithecus are as well (Hollingham, 2004; Marivaux, 2003).   The family Eosimidae includes Eosimias, Phileosiminas, Bahinia, and Phenacopithecus (Marivaux, 2005). Amphipithecus was a gibbon-sized anthropoid primate which lived 40 million years ago in Burma.  It had a 2-1-3-3 tooth arrangement (incisors-canines-premolars-molars) like prosimians, but unlike prosimians, the two halves of mandible fused as in higher primates.  The teeth are like those of fruit eating apes.  Hoanghonius is also an early Asian anthropoid (Chaimanee, 1997).  Bugtipithecus was a tiny primate classified with Amphipithecus in the family Amphipithecidae (Marivaux, 2005).Serapea eocaen seems to be related to Parapithecus.

OLIGOCENE PRIMATES 

NEW WORLD MONKEYS (platyrrhines)

monkeys

howler monkey howler
teeth
     Among other features, New World monkeys still retain 3 premolars (see illustration below) as in the prosimians while the catarrhines (old world monkeys and apes) have only two.
paralouatta

     The platyrrine lineage diverged from that of Old World monkeys and apes while South America and Africa were close to each other.  South America and Africa had been joined for millions of years in the supercontinent Gondwanaland but this supercontinent separated in the early Tertiary Period.  It is thought that New World monkeys migrated to South America from Africa just as the two continents were separating (perhaps even as a result of being washed onto South America from floating logs).  The only alternative explanation is that they descended from North American primates in the earliest of Tertiary times.  This second hypothesis doesn’t explain the homologies between New World Monkeys and fossil primates already described and no North American fossils suggest such a relationship.

     A middle Miocene fossil owl monkey, Aotus dindensis is similar to modern members of the genus, as fossils Neosaimiri fieldsi and Stirtonia tatacoensis are similar to modern genera Saimiri and Alouatta.  The rate of change in some of the New World lineages was thus less than that of the Old World lineages (Setoguchi, 1987; Gingerich, 1984; Luckett, 1975; Martin, 1990). A cebid monkey from the Early Miocene of Argentina, Killikaike, is a primitive member of the family Cebidae which possesses the enlarged forebrain characteristic of the group but lacks some of the changes of the facial bones (Tejedor, 2006).

     The fossil history of New World primates is sparse.  They had a greater range than do modern South American monkeys, occurring as far south as Patagonia and north to the Greater Antilles.  Three extinct species from the Greater Antilles form a clade: Paralouatta, Xenothrix, and Antillothrix. The Oligocene and Miocene species (Dolichocebus, Tremacebus, Homununculus, and Cebupithecia) are known from Argentina and Columbia.  Branisella is known from Bolivia in the Early Oligocene and is similar to the Late Eocene Proteopithecus of Africa, suggesting that important steps in platyrrine evolution might have occurred before they found their way to South America.  Chiiecebus is known from the Miocene (Flynn, 1998; Horovitz, 1999; Takai, 2000). chiicebus
Below are photos of skull replicas of modern New World monkeys.
marmoset marmoset
skull comparison

OLD WORLD MONKEYS AND APES (catarrhines)

apidium
    Parapithecus and Apidium were fruit eating primates with a 2-1-3-3 tooth pattern of prosimians and New World monkeys.  They may be close to the ancestral stock of both groups of anthropoids.  Unlike New World monkeys, however, they had 5 cusps on lower molars (Simons, 1995).

The early anthropoid Parapithecus was intermediate between prosimians and living anthropoids in its brain size and sensory structures (Bush, 2004)

Oligopithecus savagei lived 35 million years ago.  It possessed some prosimian characteristics in its teeth but it was the earliest primate to have the 2-1-2-3 tooth pattern that distinguishes the cusps on lower molars as in catarrhines (Delson, 1975).
propliopithecus
     Propliopithecus had the 2-1-2-3 tooth pattern but its incisors did not project forward as in modern catarrhines. Its premolars were not one-cusped as in apes and its skeleton suggests a leaping lifestyle.  Some species may have given rise to Aegyptopithecus.   Some feel that Propliopithecus also gave rise to Old World monkeys.  Several species are recognized including P. haekeli, P. markgrafi, P. ankeli, and P. chirobates (Simons, 1995; Delson, 1975).

monkey

Aegyptopithecus

AegyptopithecusAegyptopithecus

Aegyptopithecus zeuxis lived 34-33 million years ago and is considered to be ancestral to both Old World monkeys and apes.  It had dental & facial similarities to the later apes Proconsul and Dryopithecus but still maintains some prosimian aspects of the skull not found in any hominoids.  Its teeth and jaws were apelike yet it had a tail as in monkeys.  There was a large sagittal crest on the top of the skull.  It weighed 9-10 pounds, similar to the size of a gibbon.  Its limb proportions suggest it lived in the trees.  From its brain endocast, it had a small brain but an enlarged visual cortex (Simons, 1995)..

     Most Oligocene primates have tooth form and microwear similar to modern fruit-eating primates.  The teeth of Aegyptopithecus suggest that there was additional coarse material in the diet. The face and teeth of Aegyptopithecus are intermediate between that of primitive and advanced primates (Kingdon, 2003). Aegyptopithecus possessed an ethmofrontal sinus which was once thought to be a feature specific of apes (Rossie, 2002).

aegyptopithecus

     Members of the subfamily Parapithecidae were perhaps ancestral to Old World  monkeys and included Parapithecus fraasi, P. grangeri, Apidium moustafai, A. Phiomense, and Qatrania wingi (Delson, 1975).


     There are a variety of fossil old world monkeys such as those illustrated below.

old world monkeys old world monkeys

The following images are of three Old World monkeys (a Rhesus monkey skull, replicas of vervet monkey and baboon skulls) and the replica skull of the most primitive ape, the gibbon, for comparison.

skull series skull series
skull series skull series