Science
What Happened to South America’s Missing Mega-Mammals? – The New York Times
South America is filled with mammals from North America, but why more didn’t survive the reverse trip has been a natural history mystery.

After the extinction of the dinosaurs and gradual recovery of Earths biosphere, there were millions of years of animal exchanges between North America and Asia. During this time frame, the ancestors of modern horses, camels and cats crossed back and forth over land bridges. But South America spent most of this time period, the Cenozoic, as an island continent, complete with its own strange bestiary: giant ground sloths, bizarre native ungulates, tank-like armadillo relatives and saber-toothed ma…
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