http://abc.net.au/science/news/ancient/AncientRepublish_1433588.htm

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DNA taken from the teeth of ancient sabertooth cats show they were
cousins of modern cats but not direct ancestors, scientists say.

And they also shot down a theory that cheetahs may have originally
evolved from a similar-looking North American ancestor.

"Our results show that the sabertooths diverge early and are not
closely related to any living cats," write Ross Barnett of the
Henry Wellcome Ancient Biomolecules Centre in Oxford and colleagues
in the latest issue of the journal Current Biology.

Sabertoothed cats went extinct about 13,000 years ago, towards the
end of the last Ice Age, as did many other large cats that once
roamed the North American plains.

These include the Yukon scimitartoothed cat, the American lion-like
cat or Panthera atrox and a cheetah-like cat called Miracinonyx
trumani.

The only large cats that survived in the Western Hemisphere were
the puma and the jaguar.

Separate family
Sabertooths have been placed in a separate family,
Machairodontinae, from modern cats such as lions and tigers.

The researchers, which include Professor Alan Cooper from
Australia's University of Adelaide, managed to get some DNA from a
sabertooth's bones, a bit from a related Yukon scimitartoothed cat
and a sample from Miracinonyx bones found in Wyoming.

Their analysis shows that the sabertooth cats diverged early on
from the ancestors of modern cats and are not closely related to
any living feline species.

And the cat that resembled an early cheetah was not in fact a
cheetah but a relative of the modern-day puma.

"Despite its remarkable morphological similarity to the African
cheetah (Acinonyx jubatus), Miracinonyx appears to have evolved
from a puma-like ancestor, presumably in response to similar
ecological pressures," the researchers write.

Out on the plains
In other words, it chased antelope on the rolling plains of the
American Midwest just as modern cheetahs do in the African
savannah.

"It has been suggested that the cheetahs originated in the New
World and later migrated to the Old World," the researchers write.

"However, the mitochondrial sequence analysis together with recent
fossil data suggests that they originated in the Old World and that
a puma-like cat then invaded North America around six million years
ago.

"Around 3.2 million years ago, this ancestor diverged into
Miracinonyx and Puma, which is broadly contemporaneous with
increasing prairie in North America."