The journey of prehistoric crocodile-like creatures to the Caribbean islands from South America millions of years ago likely involved walking.
Once thought to be devoid of significant apex predators, the Caribbean islands have revealed through fossil discoveries in Cuba, Puerto Rico, and the Dominican Republic that they were once populated by ancient crocodyliforms known as sebecids. These creatures are distant relatives of modern crocodiles.
Although sebecids first appeared during the Cretaceous period, recent findings mark the first evidence of their presence beyond South America during the Cenozoic era, which commenced 66 million years ago. A research team comprising international experts has proposed that these predators could have roamed the Caribbean long after similar species had disappeared from the South American mainland. The geological conditions of the time, characterized by lower sea levels, might have opened sufficient land for these creatures to traverse.
In a study published in the Proceedings of the Royal Society B, researchers indicated that the physical traits of sebecids suited to a terrestrial environment, along with the timing of fossil discoveries in the West Indies, suggest they arrived in the islands during the Eocene-Oligocene transition via temporary land connections with South America or by island hopping.
Tracing Origins
During the late Eocene to early Oligocene epochs around 34 million years ago, various terrestrial carnivores inhabited South America. This diverse group included the massive sebecids, alongside giant snakes, terror birds, and metatherians, which were large marsupials. At this time, lower sea levels likely facilitated the connection of the Eastern Caribbean islands to South America through a land bridge known as GAARlandia (Greater Antilles and Aves Ridge). This land bridge is one of several historical routes that may have aided migration.
In 1999, a fragment of a tooth unearthed in Seven Rivers, Jamaica, represented the earliest fossil evidence of a ziphodont crocodyliform in the Caribbean, dating back approximately 47 million years. At that time, Jamaica was attached to a portion of the North American continent named the Nicaragua Rise. While the tooth is believed to belong to a ziphodont that is not a sebacid, its discovery alongside other vertebrate fossils in Jamaica indicates ecological parallels with regions in the American South.
The fossils unearthed in locations along the US South suggest a more complex relationship than mere shared species. The Nicaragua Rise likely served as a conduit for migration akin to the route the sebecids might have taken when establishing themselves in the Caribbean islands.
