Scientists in Brazil have discovered the first new river dolphin species since the end of World War One.  Named after the Araguaia river where it was found, the species is only the fifth known of its kind in the world.  Writing in the journal Plos One, the researchers say it separated from other South American river species more than two million years ago.  There are believed to be about 1,000 of the creatures living in the Araguaia river basin.  River dolphins are among the world’s rarest creatures.