Editing Old World monkey (section)

== Characteristics ==

Old World monkeys are medium to large in size, and range from [[arboreal]] forms, such as the [[Colobus|colobus monkeys]], to fully terrestrial forms, such as the baboons. The smallest is the [[talapoin]], with a head and body 34–37&nbsp;cm in length, and weighing between 0.7 and 1.3 kilograms, while the largest is the male [[mandrill]] (the females of the species being significantly smaller), at around 70&nbsp;cm in length, and weighing up to 50 kilograms.<ref name="EoM370-405" />

Most Old World monkeys have tails (the family name means "tailed ape"), unlike the tailless apes.  The tails of Old World monkeys are not [[prehensile tail|prehensile]], unlike those of the [[New World monkey]]s (platyrrhines).

The distinction of catarrhines from platyrrhines depends on the structure of the [[rhinarium]], and the distinction of Old World monkeys from apes depends on [[dentition]] (the number of teeth is the same in both, but they are shaped differently). In platyrrhines, the nostrils face sideways, while in catarrhines, they face downward. Other distinctions include both a tubular ectotympanic (ear bone), and eight, not twelve, premolars in catarrhines, giving them a [[dentition|dental formula]] of: {{DentalFormula|upper=2.1.2.3|lower=2.1.2.3}}

Several Old World monkeys have anatomical oddities. For example, the [[colobus]] monkeys have stubs for thumbs to assist with their arboreal movement, the [[proboscis monkey]] has an extraordinary nose, while the [[snub-nosed monkey]]s have almost no nose at all.

The [[penis]] of the male [[mandrill]] is crimson and the [[scrotum]] is [[Lilac (color)|lilac]]; the face is also brightly colored. The coloration is more pronounced in dominant males.<ref>{{cite journal|title= Developmental variables and dominance rank in adolescent male mandrills (''Mandrillus sphinx'')|year=2002 |pmid=11793410 |doi= 10.1002/ajp.1060|last1=Setchell |first1=Joanna M. |last2=Dixson |first2=Alan F. |journal=American Journal of Primatology |volume=56 |issue=1 |pages=9–25 |s2cid=25762754 }}</ref>