Fossils show that howler monkey ancestors were eating leaves 13 million years ago, shaping body size and evolution.

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 ...

Key Facts 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 ...

The “big truck, small man” phenomenon is also seen in the animal kingdom. The loudest howler monkeys were found to have the smallest packages. Hyoid bone size, which is responsible for vocalizations, ...