That is an artist's depiction. They are going off the fact that primates are monkey looking ape like, so they draw something monkey looking. Just because it looks a monkey, doesn't mean it is. Primates resemble each other a fair amount. Some people call a howler a monkey, but it is not. A howler is part of the great ape family, see how the similar traits confuse people. Now do I need to go back over high school biology; family, genus, species, kingdom, etc.
