A new river dolphin species has been discovered in Brazil—the first such discovery in nearly 100 years.
Scientists made the rare finding in the waters of the Araguaia River Basin and officially made its existence known in a study posted by the PLOS ONE scientific journal.
"It was an unexpected discovery that shows just how incipient our knowledge is of the region's biodiversity," biologist Tomas Hrbek, the study's lead author of the Federal University of Amazonas in Manaus, Brazil, told Phys.Org. "River dolphins are among the rarest and most endangered of all vertebrates, so discovering a new species is something that is very rare and exciting."
Hrbek told Phys.Org that scientists concluded the large dolphin was a new species by analyzing and comparing DNA samples of several types of dolphins from the Amazon and Araguaia river basins.
"The Araguaia dolphin is very similar to its Amazon river cousin, although somewhat smaller and with fewer teeth," Hrbek told Phys.Org, adding that National Geographic reported that the new species in central Brazil was isolated from other river dolphins (Inia geoffrensis and Inia boliviensis) in the adjacent Amazon Basin to the west by a series of rapids and a small canal. According to the study, they've been separated for more than 2 million years.
The new species was named Araguaian boto (boto means river dolphin) or Inia araguaiaensis. Hrbek said there were only about 1,000 living in the 1,630 miles of river.
From the study posted at PLOS ONE:
The species is diagnosable by a series of molecular and morphological characters and diverged from its Amazonian sister taxon 2.08 million years ago. The estimated time of divergence corresponds to the separation of the Araguaia-Tocantins basin from the Amazon basin.
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.
We anticipate that this study will provide an impetus for the taxonomic and of other taxa shared between the Araguaia and Amazon aquatic ecosystems, as well as stimulate historical biogeographical analyses of the two basins.
The last discovery of a true river dolphin was the Chinese river dolphin (Lipotes vexillifer) made in 1918 in the Yangtze River. It is now said to be extinct.
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