Prehistoric Crocodile Fossil Shows Species Went Extinct 5 Million Years Later Than Thought

We often picture the Caribbean as a place to relax and escape life’s challenges. Evidently, so too did the sebecid — a tall crocodile-like species that replaced the dinosaur as an apex predator. Paleontologists have thought the species went extinct about 11 million years ago. Instead, the creature that some describe as a cross between a greyhound and a crocodile was just biding its time on tropical islands.

Paleontologists unearthed one sebecid tooth and two in the Dominican Republic dating back 6 million years, indicating that the tall, 20-foot-long land-based predator existed five million years longer than previously thought, according to a report in the journal Proceedings of the Royal Society B.

It’s possible the predators employed the Caribbean to escape the factors that killed them off elsewhere. The Caribbean was long thought to be free of such massive predators during the early Miocene.

Pinpricks in that theory appeared about 30 years ago, when researchers discovered two sharp, serrated teeth in Cuba dating back about 18 million years. Then a similar 29-million-year-old tooth was found in Puerto Rico. However, neither fossil could definitively show just what particular predator reigned atop the Caribbean food chain.

Read More: How Crocodiles Have Survived Over 230 Million Years and Two Mass Extinction Events

Then a research team in 2023 found a tooth as well as two vertebrae. The fossils matched those of other sebecids. The finding showed that, although the Caribbean was once thought to never have hosted large predators — it may have actually served as a refuge for a species that appeared to have gone extinct elsewhere. Making that discovery and realizing its ramifications made an impact on the team.

“That emotion of finding the fossil and realizing what it is, it’s indescribable,” Lazaro Viñola Lopez, who conducted the research as a graduate student at the University of Florida, said in a press release.

Sebecids were among the last of Notosuchia, a diverse group of extinct crocodilians with a fossil record dating back to the age of dinosaurs. Although they varied in size, diet, and habitat, they differed from contemporary crocs in one way: they lived primarily on land.

So if they couldn’t swim, how did sebecids populate the Caribbean islands? A vast amount of open water separates them from mainland South America.

The research team suspects the creatures crossed a series of land bridges that connected the chain of islands. When those bridges were eventually submerged, the sebecids were left as top predators — with no easy way for competition to enter the islands and dethrone them.

Read More: As Masters of Survival and Evolution, the Crocodile Now Has Two New Species

That theory fits with observations scientists have made about other islands — that they often provide a haven for species that go extinct elsewhere. It's possible more signs of the sebecids — and perhaps other species — may emerge in the Caribbean, because their fossil potential is only now coming into focus. Paleontologists working in the Caribbean have done much of their work in the relatively low-hanging fruit of caves.

The Dominican Republic find that took them deeper — and therefore further back in time — happened by chance, when a work crew dug down to prepare a new roadbed. As such activities increase, other mysteries will either emerge or be resolved. The sebecid find in the Dominican Republic may well serve as a catalyst for paleontologists to dig deeper both there and on other Caribbean islands. If such activity increases, so to do the chances of more interesting fossil finds.

“The sebecid is only the tip of the iceberg,” Lopez said.

Our writers at Discovermagazine.com use peer-reviewed studies and high-quality sources for our articles, and our editors review for scientific accuracy and editorial standards. Review the sources used below for this article:

• Proceedings of the Royal Society B. A South American sebecid from the Miocene of Hispaniola documents the presence of apex predators in early West Indies ecosystems

Before joining Discover Magazine, Paul Smaglik spent over 20 years as a science journalist, specializing in U.S. life science policy and global scientific career issues. He began his career in newspapers, but switched to scientific magazines. His work has appeared in publications including Science News, Science, Nature, and Scientific American.