The fossils, found by US and Latin American researchers who wrote up the discovery in this week's edition of Nature, suggest that so-called New World monkeys -- ones that made it across the Atlantic from Africa to South America -- made it to North America 18 million years earlier than previously thought.
They are "the first evidence of a monkey on the North American continent before the isthmus of Panama connected it to South America 3.5 million years ago," the Panama-based Smithsonian Tropical Research Institute (STRI) said in a statement.
"It had been believed that the monkeys were restricted to South America," which millions of years ago "was a continental island with no evident connection to North America," an STRI scientist, Aldo Rincon, told AFP.
But that theory has to be revised because of the teeth found by a team led by University of Florida paleontologist, Jonathan Bloch.
"These monkey fossils from the canal show that somehow -- and we aren't really clear how -- some monkeys made it to Panama," Rincon said.