Mystery of Darwin's strange South American mammals solved

Charles Darwin thought they were the strangest animals yet discovered. One creature looked like a cross between a hippo, rhino and rodent; the other resembled a humpless camel with an elephant's trunk.  Ever since Darwin first collected the fossils about 180 years ago, scientists had been baffled about where these odd South American beasts, that went extinct just 10,000 years ago, fit on the mammal family tree.  The mystery has now been solved.  Researchers undertook a sophisticated biochemical analysis of bone collagen extracted from fossils of the two mammals, Toxodon and Macrauchenia, and demonstrated that they were related to the group that includes horses, tapirs and rhinos.