Thirteen million years ago, a group of medium-sized monkeys known for guarding their territory among the treetops with fearsome "howls" started doing something new. These monkeys, among the oldest ...

Thirteen million years ago, a medium-sized monkey known for guarding its territory among the treetops with a fearsome "howl" started doing something new. This monkey, one of the oldest known ancestors ...

A black howler monkey sits on a tree branch in the Amazon Rainforest, Brazil. The surrounding forest shows dense vegetation and tall trees. Wildlife like this monkey is common in the forests of the ...

13.3-million–13.6 million-year-old fossils from an extinct relative of the howler monkey show signs of being the first leaf-eating primate in South and Central America. Fossils from jaws of Stirtonia ...