Researchers found first new species of river dolphin since World War One.
The Brazilian aquatic animal is believed to have separated from its South American ancestors about two million years ago, the BBC reported.
About 1,000 of the dolphins are believed to live in the Araguaia river basin. There are only four known river dolphin species and three of them are on the IUCN Red List as "critically endangered."
"It was something very unexpected, it is an area where people see them all the time, they are a large mammal, the thing is nobody really looked. It is very exciting," lead author Dr. Tomas Hrbek of the Federal University of Amazonas said, according to BBC News.
The team noticed the Araguaia river dolphin was smaller than other species and had less teeth, but they found the real evidence of a species separation in the animal's DNA.
"In science you can never be sure about anything," Hrbek said, the BBC reported. "The groups that we see, the haplotypes, are much more closely related to each other than they are to groups elsewhere. For this to happen, the groups must have been isolated from each other for a long time.
"The divergence we observed is larger than the divergences observed between other dolphin species," he said.
The researchers plan to name the new species "Araguaian Boto, or Boto-do-Araguaia," the BBC reported.
The team is concerned about the newly-discovered species because it appears to have low "genetic diversity." Humans have been taking over the river, which is also bad news for the dolphins.
"Since the 1960s the Araguaia river basin has been experiencing significant anthropogenic pressure via agricultural and ranching activities, and the construction of hydroelectric dams," the authors wrote in their study, the BBC reported.
The dolphins often rob fishing nets, which encourages fishermen to harm them.
