Recent discoveries in the Dominican Republic have provided new insights into the extinction of sebecids, a group of crocodile-like reptiles that thrived long after the mass extinction event that ended the age of dinosaurs. These findings, reported in the Proceedings B of the Royal Society, reveal that sebecids persisted in the Caribbean approximately 4.5 million years ago, several million years later than previously believed. The fossils suggest that these reptiles played a significant role in ancient Caribbean ecosystems, shedding light on their interactions with other fauna during this time.
The end of the Cretaceous Period, marked by the extinction of non-avian dinosaurs 66 million years ago, paved the way for mammals to flourish. In South America, however, the sebecids continued to dominate as apex predators, surviving long past their dinosaur counterparts. Unlike their modern relatives, sebecids possessed elongated limbs positioned beneath their bodies, equipping them for terrestrial hunting. Their specialized teeth and sleek body form enabled them to effectively navigate their habitats, but they ultimately disappeared from South America around 10 million years ago.
While fossils of sebecids have been typically found in South America and Europe, recent discoveries in the Caribbean highlighted a curious phenomenon. Fossils, especially serrated teeth, had been discovered on various island sites, including Cuba and Puerto Rico, but their origins remained a mystery. A team led by vertebrate paleontologist Lazaro Viñola López unearthed vertebrae and a tooth in the Dominican Republic, confirming these teeth as sebecid remnants. This represents the first record of sebecids in the Caribbean, suggesting that they may have migrated to the islands through ancient land connections or by drifting on vegetation.
This Dominican find dates to around 4 to 7 million years ago, starkly younger than other fossil records of similar teeth found across the Caribbean, indicating that sebecids survived in the region while their continental relatives went extinct. The remains of these creatures emphasize that they were the last representatives of notosuchians, a wider group of reptiles that first emerged during the Jurassic Period, suggesting a remarkable continuity of predator types in the Caribbean until relatively modern times.
The findings shift previously held assumptions about the Caribbean ecosystem, particularly concerning the absence of significant terrestrial predators, which might have influenced the evolution of local avifauna. It’s been posited that unique bird species turned to flightlessness in part due to the lack of land-based threats. The presence of two-meter-long sebecids indicates that these predators were still influencing the ecology when such evolutionary transitions were occurring among bird populations.
Finally, the implications of these findings extend beyond mere chronology; they alter our understanding of the Caribbean’s evolutionary narrative. Not only do they underscore the survival of unique reptilian fauna into recent geological epochs, but they also demonstrate the complex interrelationships within ecosystems that existed long after the dinosaurs vanished. The existence of formidable carnivores like sebecids alongside diverse bird species until fairly recently reveals a rich tapestry of life that shaped the biological history of the Caribbean islands.
