Imagine a crocodile with the speed and build of a greyhound, sprinting across land on long, muscular legs and slicing into prey with jagged teeth. This isn’t a creature of fantasy, nor is it a dinosaur. It’s a sebecid, one of the strangest and most formidable predators ever to stalk ancient landscapes. For decades, paleontologists believed that these land-dwelling crocodyliforms had vanished from the Earth around 11 million years ago, confined to the fossil record of South America. But that story began to unravel—piece by fossilized piece—when strange teeth started turning up in the Caribbean.
What unfolded from these discoveries would change everything scientists thought they knew about the ecology, geography, and evolutionary history of the islands. The Caribbean, long assumed to have lacked large terrestrial predators in deep time, may have once echoed with the thunder of running sebecids.
The First Clues: Teeth in the Tropics
It all started with a puzzle. In the dry heat of Cuba’s ancient outcrops, paleontologists discovered two curious fossil teeth over 30 years ago. They were unlike anything researchers had expected to find on the island. Sharp, tapered, and lined with tiny serrations, the teeth screamed carnivore. But not just any carnivore—a specialist, an apex predator designed to tear into flesh. And yet, no known predator from the Caribbean fit the profile.
The confusion deepened when, years later, another tooth was unearthed in Puerto Rico. This one was even older, dating back about 29 million years. Still, a tooth alone could only tell part of the story. It was like finding a fingerprint at a crime scene without knowing who it belonged to. For decades, the identity of these Caribbean carnivores remained a mystery.
The Breakthrough: Bones from the Dominican Republic
Then came the discovery that would shift the scientific paradigm. In 2023, during a road-cutting project in the Dominican Republic, construction workers unknowingly exposed layers of rock rich with ancient secrets. Paleontologists were quick to respond. Amid the crumbled stone, researchers discovered not just another tooth, but two fossilized vertebrae nearby. Together, these fragments were the smoking gun.
The bones belonged to a sebecid—an extinct lineage of land-dwelling crocodyliforms that had thrived in South America after the extinction of the non-avian dinosaurs. It was a moment of revelation. The Caribbean, thought to be devoid of such predators, had in fact sheltered them long after they disappeared from the mainland. Sebecids had not only reached the islands—they had survived there for millions of years.
As the implications sank in, one thing became clear: the Caribbean had its own chapter in the epic story of sebecid evolution, and paleontologists had only just begun to turn the pages.
Who Were the Sebecids?
To understand the magnitude of this discovery, one must first meet the sebecids. These weren’t your average crocodilians lounging in swamps. Sebecids were members of the Notosuchia, a clade of extinct crocodyliforms that date back to the age of dinosaurs. Unlike their modern, semi-aquatic relatives, notosuchians were adapted to life on land. They came in all shapes and sizes—some were herbivores, others omnivores, but the sebecids were pure predators.
Built for speed and power, sebecids had tall skulls and ziphodont teeth—meaning each tooth was laterally compressed with sharp edges and fine serrations, perfect for slicing flesh. They walked and ran on upright limbs, more like a dog than a crocodile, and some species reached up to 20 feet in length. They were armored too, with osteoderms—bony plates embedded in their skin—that offered protection against other predators and prey.
When the asteroid struck 66 million years ago, wiping out the dinosaurs and much of the planet’s biodiversity, nearly all notosuchians perished. But sebecids hung on in South America, rising to fill the ecological gap left by the vanished theropods. For tens of millions of years, they dominated their ecosystems, a reminder that crocodilians weren’t just relics—they were survivors.
Island Oddities: How Did Sebecids Reach the Caribbean?
But how did a terrestrial predator that evolved in South America make its way across the sea to the Caribbean islands? For decades, such a journey was considered unlikely, if not impossible. Crocodiles might be strong swimmers, but sebecids were landlocked sprinters, poorly suited for open-ocean voyages.
The discovery of sebecid fossils in the Dominican Republic provides compelling support for an intriguing theory: the GAARlandia hypothesis. According to this idea, a temporary land bridge—or a chain of stepping-stone islands—once connected northern South America to the Greater Antilles around 33 to 35 million years ago.
This ephemeral corridor, named GAARlandia after the Greater Antilles and Aves Ridge, could have allowed animals to migrate northward across what is now open sea. Fossils of rodents, sloths, and other terrestrial animals in the Caribbean already hinted at this connection. Now, with the discovery of sebecid bones, the case for GAARlandia grows even stronger.
If these predators made the journey and thrived, it suggests the Caribbean’s ancient ecosystems were more complex—and more dangerous—than anyone had imagined.
A Ghost in the Ecosystem
What makes this discovery especially striking is how unexpected it was. Modern Caribbean ecosystems don’t hint at the presence of such a large terrestrial predator. Instead, today’s top hunters are modest in comparison: snakes, raptors, small carnivorous mammals. Crocodiles remain, but they’re aquatic and largely confined to coastal zones.
The absence of a large, land-based apex predator left a gaping hole in scientists’ understanding of the region’s ecological history. With the confirmation of sebecids, it’s clear that ancient Caribbean food webs once looked very different. The fossil evidence rewrites the narrative and challenges assumptions about island ecology.
As Jonathan Bloch of the Florida Museum of Natural History put it, “You wouldn’t have been able to predict this looking at the modern ecosystem.” The fossil record had kept its secrets well—but no longer.
Fossils in Fragile Landscapes
Uncovering fossils in the Caribbean is a race against time. The region’s climate, with its powerful storms and dense vegetation, rapidly erodes exposed rock and conceals outcrops. Fossil-bearing sites are rare and often transient. As Lazaro Viñola Lopez, the lead author of the sebecid study, noted, “Outcrops don’t last too long. If you’re looking in a few years, it will be gone.”
Many of the region’s most important fossils have been found during construction work or by sheer luck. Such was the case with the Dominican Republic site. Graduate student Elson Core, conducting stratigraphic research at the time, stumbled upon the fossil bed while roadwork was being done. Had he arrived months later, the site might have been lost forever.
This makes the role of local scientists and institutions even more vital. Caribbean researchers are increasingly leading expeditions, responding quickly to discoveries, and building a deep-time narrative of their islands. In many ways, it’s a scientific renaissance—a reclaiming of ancient stories hidden beneath their feet.
Islands as Time Capsules
The idea that islands can preserve species long after they’ve vanished from the mainland isn’t new. Biologists and paleontologists alike recognize islands as museums of biodiversity—refugia where evolutionary lineages can persist in relative isolation. The Caribbean appears to have played this role for the sebecids.
It also preserved records of other ancient creatures. Recent discoveries have included the first Caribbean fossils of mosasaurs, massive marine reptiles that ruled the seas, and the oldest known remains of ground sloths in Hispaniola. These finds, like the sebecid bones, are reshaping how we view the region’s past.
They also point to the urgency of exploration. Much of the tropics remain paleontologically underexplored, not because they lack fossils, but because the environments are so difficult to access. Yet, these regions are key to understanding how life survived mass extinctions and evolved in isolation.
What Comes Next
The reappearance of sebecids in the fossil record after their supposed extinction on the mainland reveals not an end, but a continuation—one we’re only just beginning to understand. The Caribbean, long viewed through a limited ecological lens, now emerges as a place of evolutionary intrigue and unexpected resilience.
The discovery also prompts new questions. How long did sebecids persist on the islands? What other apex predators might have coexisted with them? Could their extinction have been linked to environmental change—or perhaps the arrival of early humans?
As Viñola Lopez remarked, “The sebecid is only the tip of the iceberg.” For Caribbean paleontology, the best may be yet to come. Road cuts, dry riverbeds, and windswept limestone may still hold the remains of ancient beasts waiting to be found.
A Predator Reborn in Memory
In life, sebecids were swift and terrifying, the undisputed kings of their domain. In death, their bones lay hidden for millions of years, undisturbed beneath Caribbean soil. Now, as they rise again through the careful work of science, they remind us of a forgotten past—of predators on islands, of vanished ecosystems, and of the stories waiting in stone.
With every discovery, the Caribbean sheds its image as a quiet backwater of evolution. Instead, it stands revealed as a vibrant theater of survival, adaptation, and extinction—where even a land-bound crocodile could become the stuff of legend.
Reference: A South American sebecid from the Miocene of Hispaniola documents the presence of apex predators in early West Indies ecosystems, Proceedings of the Royal Society B: Biological Sciences (2025). DOI: 10.1098/rspb.2024.2891. royalsocietypublishing.org/doi … .1098/rspb.2024.2891
Loved this? Help us spread the word and support independent science! Share now.