River Dolphin Discovered In Brazil Marks The First New River Species Since 1918; Sadly, It's Already Endangered

By Josh Lieberman on January 23, 2014 3:50 PM EST

dolphin skull
A new river dolphin species has been discovered in Brazil, the first new river dolphin species since 1918. (Photo: PLoS One)

A new species of river dolphin has been discovered in the Araguaia River basin in Brazil, marking the first new river dolphin species discovery since 1918. With only five known species of river dolphin in the world, three of which are now known to inhabit the Amazon basin, river dolphins are "some of the rarest and most endangered of all vertebrates," the researchers write in a study published yesterday in PLoS One. 

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The new river dolphin species, Inia araguaiaensis, was already known to live in the Amazon waters, but scientists weren't sure it was a separate species from the other Amazon dolphins. Since the new species is cut off from the other river dolphin species by rapids, scientists suspected that they might be a unique species. 

Led by Tomas Hrbek, an evolutionary biologist at the Federal University of Amazonas in Manaus, Brazil, the researchers compared nuclear and mitocondrial DNA of all three Amazon river dolphin species and found that the DNA was indeed different among the three. The researchers also compared skulls from the three river dolphin species, which turned out to be slightly different sizes and contained differently shaped teeth. Hrbek and his team concluded that they had a new species on their hands, once which became isolated from the other river dolphin species for over 2 million years, after the river's pattern shifted and changed.        

"[The new dolphin] is very similar to the other ones," said Hrbek. "It was something that was 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."

What's less exciting is the fact that there are very few of the new species in existence, according to Hrbek, and that construction of dams on both the Araguaia and Tocantins rivers could kill off the newly discovered river dolphin. "Its future is pretty bleak," said Hrbek. "The Araguaia-Tocantins basin suffers huge human disturbance and there are probably less than 1000 I. araguaiaensis in existence." 

River dolphins differ from their more populous and well-known cetacean cousins in a number of ways. River dolphins have snouts that are four times as long as marine dolphins, a useful thing when extracting fish from logs and other hiding places. River dolphins have worse vision than the marine variety, a result of living in dark and muddy waters. They also lounge around more than marine dolphins.

In 2006, the Chinese river dolphin, or baiji, was declared "functionally extinct" (meaning that the few remaining members of the species could not repopulate it) following decades of industrialization of the Yangtze River, the dolphin's only habitat. A month-long survey of the river in 2006 turned up no individuals. If the the baiji is in fact extinct, it has the unfortunate distinction of being the first known aquatic mammal to become extinct since the 1950s, and would be the first cetacean species to ever become extinct as a result of direct human actions.

In order to avoid ending on such a depressing note, here are some pictures of a rare bubblegum pink Amazon river dolphin.

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