New Species of River Dolphin Discovered in Brazil is First in Nearly 100 Years

A rare, new species of river dolphin has been identified for the first time in nearly a century, and the scientists who found it say it should be given endangered status immediately.

Delivering their report on the new river dolphin species in the open-access journal PLOS One, the researchers said their discovery highlights the "immensity of the deficit in our knowledge" in the region's biodiversity.

Working the the Amazon River's Araguaia basin, a team of scientists from the Federal University of Amazonas in Manaus, Brazil, found a group of river dolphins, also known as botos, living separated from other populations in the river. Upon closer examination, they realized that the botos were genetically and morphologically different from other known river dolphin species.

They have proposed naming the new species the Araguaian boto (Inia araguaiaensis).

True river dolphins are among the rarest and most endangered of all vertebrates, the researchers said. This new river dolphin species is only the fifth of its kind known to science. The last time a new river dolphin species was found was 1918. Researchers estimate that there about about 1,000 Araguaian botos currently living in the river basin.

The scientists contend that the Araguaian boto likely separated from other South American boto species more than 2 million years ago.

Compared to related river dolphins, the Araguaian boto is smaller and has a different number of teeth, but most of their differences are genetic.

"We looked at the mitochondrial DNA which is essentially looking at the lineages, and there is no sharing of lineages," the study's lead author Tomas Hrbek said, according to the BBC.

"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.

Based on what the researchers say is low genetic diversity among the specimen samples and a relatively low population, coupled with human activity in their natural environment, Hrbek and his colleagues suggest the species be considered as endangered and - at a minimum - be listed as "vulnerable" on the International Union for the Conservation of Nature (IUCN) Red List. Three of the four previously known river dolphin species are listed as "threatened" on the Red List.