fewer teeth and are more sexually dimorphic in terms of body size and anatomy.

The traits that separate New World simians from Old World simians are the nostrils and their dentation (teeth). New World simians have broad noses with forward facing nostrils and three premolars in each quadrant of the mouth, while Old World simians have narrower noses with downward facing nostrils and a narrow septum and only have two premolars.