Researchers have discovered a new species of river dolphin in Brazil, named the "Araguaian boto," the first such finding in nearly 100 years. Genetic work shows that it diverged from other river dolphins more than 2 million years ago. The animals live in the Araguaia River, which is not a tributary of the Amazon River and separated from that watershed about the time the animals diverged from the common ancestor they share with Inia geoffrensis, the Amazon river dolphin.  

This species, named Inia araguaiaensis, becomes the fifth true river dolphin, amongst the rarest and most endangered animals. The last river dolphin species to be described, in 1918, was the Chinese baiji, which went extinct in about 2006. Three of the four previously known species are all threatened with extinction, according to the International Union for Conservation of Nature.