Primates include lemurs, monkeys and apes. We're primates too! There is no single feature that is unique to primates versus other mammals, but there is a combination of characters that set primates apart, including opposable thumbs for grasping, flat nails rather than claws in most species, forward facing eyes, and relatively large brains. Some of the primates here include western lowland gorillas, Sumatran orangutans, ring-tailed lemurs and golden lion tamarins. When you visit the Zoo, you'll find most of the primates at PECO Primate Reserve and The Rare Animal Conservation Center, but there are also some at the Small Mammal House and other locations.