A new fossil and DNA analysis traces how dozens of sloth species responded to climate shifts and humans. Just two small tree-dwelling sloths remain today.

An analysis of the sloth family tree suggests three different groups of the animals evolved to gigantic sizes in response to ...

Some species in the genus Arkys are not triangular at all and instead resemble bird droppings as further camouflage. These ...

For the first time, scientists have created a comprehensive evolutionary tree of all known bird species, synthesizing data ...