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The scientists suggest that the discovery will have widespread implications on how we look at aquatic ecosystems.

“We anticipate that this study will provide an impetus for the taxonomic and conservation reanalysis of other taxa shared between the Araguaia and Amazon aquatic ecosystems, as well as stimulate historical biogeographical analyses of the two basins,” the study said.

The scientists estimate that there are about 1,000 of the creatures living today.

River dolphins are quite different from their sea-based cousins, having much longer snouts used to hunt for fish and other food buried in river mud.

The reason the dolphins haven’t been discovered before is because people just haven’t looked, the researchers say.

“It is very similar to the other ones,” lead author Dr. Tomas Hrbek, from the Federal University of Amazonas, told the BBC. “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.”

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

The distinction between the two species was determined through analysis of their DNA. There are some claims, however, that the new dolphins really aren’t that different than the traditional Amazon river dolphins.

“In science you can never be sure about anything,” Dr. Hrbek said. “We looked at the mitochondrial DNA, which is essentially looking at the lineages, and there is no sharing of lineages.”

River dolphins are heavily endangered, with many species very much at risk of extinction. One of the reasons behind this is fishing.

“The dolphins are at the top of the line, they eat a lot of fish,” Dr. Hrbek told the Daily Mail. “They rob fishing nets so the fishermen tend to not like them — people shoot them.”