Dr. Alex Hastings, a fossil crocodilian specialist at Georgia Southern University, and Jonathan Bloch, a vertebrate paleontologist at the Florida Museum of Natural History, reported the discovery of the first Central American crocodilian fossils ever discovered in the Mar. 4, 2013, issue of the Journal of Vertebrate Paleontology.
The partial skulls of two new species of caiman, fresh water relatives of alligators, were exposed by excavations associated with the expansion of the Panama Canal in rocks dated from 19.83 and 19.12 million years old.
Culebrasuchus mesoamericanus are the first fossil crocodilian fossils recovered from all of Central America. The fossils are early relatives of a caiman species that is exclusive to South America at the present time.
The discovery indicates that caimans moved north from South America at least 10 million years earlier than mammals based on all known fossil records.
Present day caimans cannot excrete excess salt from their bodies. This limitation means caimans only occupy fresh water areas and can only cross small distances of salt water.
The discovery has led the researchers to postulate that Central and South America were much closer to each other 19 million years ago than previously thought. The uplift of the Isthmus of Panama 2.6 million years ago formed a land-bridge that has long thought to be the crucial step in the interchange of animals between the Americas.
This new species of caiman argues for an earlier dispersal of crocodilians and possibly other reptiles between North America and South America by an as yet undefined and undiscovered path.
Insufficient evidence exists in the fossil discovery to indicate that Culebrasuchus mesoamericanus had the capacity to excrete excess salt and could therefore traverse longer distances in salt water and reach Central America by water.