It has been discovered that relatives of the alligator swam to North America over 19 million years ago, ten million years before mammals.
The discovery was made by researchers from the University of Florida and the Smithsonian Tropical Research institute. Digging near the Panama Canal, they discovered fossils from rocks 19.12 to 19.83 million years old. What they uncovered were partial skulls belonging to two new species of caiman, which is a relative of the alligator that resides solely in South America. The find has important implications for understanding animal migration between the American continents.
"These are the first crocodilian skulls recovered from all of Central America," says Georgia Southern University's Alex Hastings. "They fill a gap in evolution between the alligators of North America and the caimans of South America. It's quite incredible."
The find is surprising because it suggests that the caimans spread north from South America during the early Miocene era, which occurred more than ten million years before mammals began to spread. North and South America were separate at this time, and so it is interesting to discover that that is when the caimans spread, given their inability to remain in salt water for extended periods. Thus, it appears that Central and South America may have been much closer to each other at this time than ever before believed.
"Somehow, they were able to cross over from South America when it was completely isolated by seaways," says Florida Museum of Natural History paleontologist Jonathan Bloch, "this is one of the mysteries that will drive further inquiry and research in this region."
The fossil hunt which led to these discoveries was called the Panama Canal Project. The study is published in the Journal of Vertebrate Paleontology. It sheds light on an area that has been somewhat murky for scientists studying the fossil record in Central America.
"We are starting to understand that while the mammals in Panama 19-21 million years ago were very similar to those found in Mexico, Texas and Florida at that time, the reptiles tell a different story," Bloch says.
