for National Geographic News
A 66-million-year-old tooth found in India has paleontologists questioning their theories about the rise and spread of hoofed mammals.
The tooth may have belonged to one of the condylarths, according to a new study led by Guntupalli Prasad of the University of Jammu in India.
This group of primitive mammals included the ancestors of modern hoofed animals such as goats, horses, cows, sheep, and deer.
But the newfound molar is about three million years older than the earliest known condylarth specimen.
This places it on the Indian subcontinent at a time when the landmass was a drifting island that had just broken away from the supercontinent called Gondwana.
The find, described in this week's issue of the journal Science, may help fuel a controversial theory that what is now India was the prehistoric source of many plant and animal species.
"The fossil record shows [for example] that the Indian subcontinent was the center of origin for whales" 55 million years ago, Prasad said.
"Similarly, many researchers had postulated that mammalian groups may have originated from basal Gondwanan stocks during the northward flight of India and finally dispersed to Asia when India collided with the Asian mainland around 55 million years ago."
But the tooth's ultimate identification is far from certain.
J. David Archibald, an evolutionary biologist at San Diego State University, believes that the molar certainly belonged to an ancient mammal, but that we cannot be certain what type.
"It has interesting biogeographic implications, whatever it is," he said.
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