A new species of river dolphins were reportedly found swimming in Araguaia River Basin in central Brazil.

For more than 12 weeks, researchers from the Universidade Federal do Amazonas in Manaus, Brazil, led by Tomas Hrbek, studied and observed about 120 river dolphins or botos. These botos are proposed to be named Araguaian boto or inia araguaiaensis.

During that period, they tested the dolphins' DNA and concluded that the Araguaian botos are different from other species of botos. They presented some undeniable size differences in the cranial features the number of teeth of these new species.

These physical and genetic differences strongly suggest that the new river dolphins have been separated from other dolphin species for roughly two million years now.

The researchers have made "a strong case based on the data," said Howard Rosenbaum, the director of Wildlife Conservation Society's Ocean Giants program in New York to National Geographic. It is "amazing because we're starting to get insights into how these animals become distinct species."

The river dolphins are one of the most endangered species in the world. There were only four known species and three of those are listed by the International Union for Conservation of Nature (IUCN) as "threatened."

The researchers wrote in their report that the Araguaian boto should be listed as "vulnerable" by IUCN. They wrote, "This discovery highlights the immensity of the deficit in our knowledge of Neotropical biodiversity, as well as vulnerability of biodiversity to anthropogenic actions in an increasingly threatened landscape."

Nonetheless, all river dolphins face many threats that limit their reproduction opportunities. These threats include dam constructions and fishermen who kill dolphins.

The Araguaia River basin has been experiencing major pollution brought by the human's agricultural and ranching activities over the last five decades. One of it was the construction of the hydroelectric dams which caused a major disruption on the ecosystem affecting the animals living in the river.

However, Rosenbaum said that extensive research needs to be carried out first before we can fully debate on how these threats may affect the survival of these species.

The study was published in the Jan. 22 issue of PLOS ONE.