In a surprise to paleontologists, ancient teeth discovered in the hot scrublands of central Mexico belong to a water-loving otter that roamed North America six million years ago.

Found 120 miles from the nearest coastline, the fossil opens up an entirely new discussion about the movements of mammals across the continent millions of years ago.

The teeth belong to an extinct otter species called Enhydritherium terraenovae, says Jack Tseng at the University of Buffalo, whose team describes the find this week in the journal Biology Letters. This species had previously been found only in coastal regions in Florida and California, suggesting it was dependent on coastal environments like its modern relatives.

In March, Tseng and his colleagues were in the