Old World Monkeys Stephen R Frost, University of Oregon, Eugene, Oregon, USA Alfred L Rosenberger, Brooklyn College-City University of New York, Brooklyn, New York, USA Walter C Hartwig, Touro University, Vallejo, California, USA Based in part on the previous version of this Encyclopedia of Life Sciences (ELS) article, Old World Monkeys by Walter Carl Hartwig and Alfred L Rosenberger. Old World monkeys, or cercopithecoids, are a diverse and widespread group of primates found throughout Africa and Asia. They are characterised by their specialised molar teeth, quadrupedal running behaviour, often spending more time on the ground than other primates, as well as their often large and complex social groups. They survive in the widest range of habitats of any nonhuman primates, with some species restricted to humid tropical forests whereas others are found in mountains and deserts. There are two main groups: the cercopithecines, which have cheek-pouches and include macaques, baboons, manga- beys, vervets and guenons; and the colobines, character- ised by complex stomach anatomy that allows them to digest leaves and which include langurs, proboscis mon- keys, doucs and snub-nosed monkeys and colobus mon- keys. Although they are termed ‘monkeys’ they are more closely related to apes and humans (hominoids) than they are to the monkeys of Central and South America. Introduction Old World monkeys, technically termed cercopithecoids, are the most successful evolutionary radiation of nonhu- man primates in the world (Grubb et al., 2003; Brandon- Jones et al., 2004). They live in the tropical and temperate regions of Africa and Asia along with many adjacent Islands. Relative to other primate groups they are geo- graphically widespread, taxonomically diverse, and eco- logically flexible. They have spread to occupy higher latitudes and altitudes than any other primate excluding humans. Scientists currently recognise 20 different living genera divided into two distinct adaptive radiations: the cercopithecines, who live in terrestrial and arboreal habi- tats and forage for a variety of foods, but mostly fruit; and the colobines, who live in arboreal habitats and rely upon leaves and seeds for major portions of their diet. Interest- ingly, cercopithecoids have achieved this diversity in spite of being less varied anatomically and in their social behaviour than other primate groups (Szalay and Delson, 1979; Di Fiore and Rendall, 1994; but see Fleagle et al., 2010). Cercopithecoids also have an extensive fossil record, especially in Africa, which shows that Old World monkeys are both a relatively recent adaptive radiation and that in the past they were even more diverse and occupied an even greater geographic, taxonomic and ecological range (Jablonski, 2002; Jablonski and Frost, 2010). Basic Biology Old World monkeys are catarrhine primates, and as such share anatomical features with modern apes and humans (hominoids) but are distinct from the New World monkeys, which are a separate radiation of anthropoid (Szalay and Delson, 1979; Fleagle, 1999). These catarrhine features include narrow and downward-facing nostrils, two pre- molar teeth, a complete bony auditory tube (tympanic bone) extending from the middle ear to the external ear, trichromatic colour vision, and ischial callosities, or ‘sitting pads’. Old World monkeys are further distinguished from other catarrhines by their specialised molar teeth, termed ‘bilophodont’ for the two parallel transverse ridges that cross the width of each crown and link the four cusps as paired sets. These lophs are not independent crests; rather, they are the effect of altering, or folding, the normally rounded surfaces of the inner sides of each cusp into ridges. Old World monkeys also have specialisations of their body for quadrupedal running. As primates, they are medium to large in size, ranging from the talapoin monkey, the smallest modern catarrhine at slightly more than 1 kg, to male mandrills and baboons at 30 kg (Delson et al., 2000). They are also often highly sexually dimorphic with males being much larger than females and Introductory article Article Contents . Introduction . Basic Biology . Diversity . Habitats and Abundance . Habits and Life Histories . Fossil History . Phylogeny Online posting date: 15 th August 2011 eLS subject area: Evolution & Diversity of Life How to cite: Frost, Stephen R; Rosenberger, Alfred L; and Hartwig, Walter C (August 2011) Old World Monkeys. In: eLS. John Wiley & Sons, Ltd: Chichester. DOI: 10.1002/9780470015902.a0001561.pub2 eLS & 2011, John Wiley & Sons, Ltd. www.els.net 1