By Will Dunham WASHINGTON (Reuters) – To 19th century British naturalist Charles Darwin, they were the strangest animals yet discovered, one looking like a hybrid of a hippo, rhino and rodent and another resembling a humpless camel with an elephant's trunk. Ever since Darwin first collected their 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. Researchers said on Wednesday a sophisticated biochemical analysis of bone collagen extracted from fossils of the two mammals, Toxodon and Macrauchenia, demonstrated that they were related to the group that includes horses, tapirs and rhinos. Some scientists previously thought the two herbivorous mammals, the last of a successful group called South American ungulates, were related to mammals of African origin like elephants and aardvarks or other South American mammals like armadillos and sloths.
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