Giant carnivorous crocodiles were once the Caribbean’s top predators

By Stephen Beech

Giant crocodile ancestors "built like a greyhound" were the top predators in the Caribbean 20 million years ago, reveals new research.

The massive carnivores, called sebecids, stood tall - with some species reaching 20 feet in length, say scientists.

The fearsome hunters were only previously known to have dominated South American landscapes after the extinction of dinosaurs until about 11 million years ago.

But the new study, published in the journal Proceedings of the Royal Society B Biological Sciences, shows they also lived on islands in the Caribbean.

The breakthrough was triggered when paleontologists unearthed strange fossilized teeth on an island.

Professor Jonathan Bloch, curator of vertebrate paleontology at the Florida Museum of Natural History, said: "The first question that we had when these teeth were found in the Dominican Republic and on other islands in the Caribbean was: what are they?”

Three decades earlier, researchers had uncovered two roughly 18 million-year-old teeth in Cuba.

With a tapered shape and small, sharp serrations specialized for tearing into meat, it clearly belonged to a predator at the top of the food chain.

But scientists didn’t think such large, land-based predators ever existed in the Caribbean.

The mystery deepened when a 29-million-year-old tooth was found in Puerto Rico.

The teeth alone weren't enough to identify a specific animal, and the matter went unresolved.

But that changed in 2023 when a research team unearthed another fossilized tooth in the Dominican Republic, accompanied by two vertebrae.

The fossils were identified as belonging to a sebecid.

And it emerged that the Caribbean, far from never having large, terrestrial predators, was a refuge for the last sebecid populations at least five million years after they went extinct everywhere else.

Study lead author Lazaro Viñola-Lopez, who conducted the research as a graduate student at the University of Florida, knew his team had come across something exceptional when they unearthed the fossils.

He said: “That emotion of finding the fossil and realizing what it is, it’s indescribable.”

The research team explained that sebecids were the last surviving members of the Notosuchia, a large group of extinct crocodilians with a fossil record that extends back into the age of dinosaurs.

They represented a wide range in size, diet and habitat and were "notably different" from their crocodile relatives, as most of them lived entirely on land.

The team said sebecids acted like carnivorous dinosaurs, sprinting after prey on their four long, agile limbs and tearing through flesh with their notorious teeth.

Some species had protective armor made of bony plates embedded in their skin.

The mass extinction event 66 million years ago that wiped out non-avian dinosaurs nearly destroyed notosuchians as well.

In South America, only the sebecids endured, and with the dinosaurs gone, they quickly rose to be the apex predator.

The researchers said finding sebecid fossils in the Dominican Republic site was possible because local work crews happened to be cutting a road directly through it.

Elson Core, a graduate student from the University of Puerto Rico at the time, came across the fossil beds while conducting stratigraphy research and alerted his colleagues.

Viñola-Lopez learned about the site through fellow paleontologists and was eager to plan a visit for fieldwork.

The research team say the open sea separating the Caribbean islands and mainland South America would have posed a "serious" challenge for a terrestrial sebecid to swim across.

In finding the fossils, the team revealed possible evidence in support of the GAARlandia hypothesis - a theory that suggests a pathway of temporary land bridges or a chain of islands once allowed land animals to travel from South America to the Caribbean.

If, as scientists hypothesize, the serrated teeth discovered on other Caribbean islands also belonged to a sebecid, the history of the giant reptiles extends beyond the Dominican Republic.

Bloch said: “You wouldn’t have been able to predict this looking at the modern ecosystem.

“The presence of a large predator is really different than we imagined before, and it’s exciting to think about what might be discovered next in the Caribbean fossil record as we explore back further in time.”

Viñola-Lopez added: “The sebecid is only the tip of the iceberg.”