Giant crocodile in the Caribbean? Fossils reveal a lost apex predator

Sebecid fossils are changing everything we thought we knew about the ancient Caribbean. Imagine a crocodile built like a greyhound – tall, fast, and fully land-dwelling. These agile predators, some stretching up to 20 feet long, once ruled South American landscapes after the extinction of the dinosaurs.

Scientists believed they vanished around 11 million years ago. But a surprising discovery in the Caribbean tells a different story – one that begins with a few unusual fossilized teeth.

A fossil discovery changed the story

Back in the 1990s, scientists discovered a pair of fossilized teeth in Cuba. The teeth, about 18 million years old, were serrated and sharp – built for tearing meat.

Then came another one in Puerto Rico, dated to 29 million years ago. The shape of these fossils clearly pointed to a large predator.

But researchers were baffled. Until then, they thought the Caribbean had no land predators of that size. Without more bones to go on, the mystery sat unsolved.

Then in early 2023, something changed. A new fossil tooth turned up in the Dominican Republic, but this time it came with two vertebrae. It was a small clue, but it changed everything.

Large predators in the Caribbean

The fossils confirmed the presence of a sebecid. That meant the Caribbean had been a safe haven for these large, land-based predators. They were still roaming these islands five million years after disappearing everywhere else.

This new discovery comes from a research team led by scientists from the University of Florida.

“That emotion of finding the fossil and realizing what it is, it’s indescribable,” said Lazaro Viñola Lopez, the study’s lead author.

Crocodiles that ran like dinosaurs

Sebecids were part of a long-extinct family of crocodile relatives called notosuchians. Unlike modern crocodiles that lurk in rivers and swamps, sebecids were fully land-dwelling.

They ran on strong limbs and hunted like the carnivorous dinosaurs that came before them. Some were enormous.

Sebecids had armored bodies with tough bony plates beneath their skin. Their teeth were made for slashing meat, not catching fish.

When the mass extinction 66 million years ago wiped out most life, only the sebecids from the notosuchian line managed to survive in South America. With dinosaurs gone, they rose to dominate the food chain.

Sebecids may have crossed the sea

How did a sebecid get to the Caribbean? The ocean has always been a serious barrier for land animals. That’s where the GAARlandia hypothesis comes in.

The theory suggests there was once a chain of temporary land bridges or stepping-stone islands between South America and the Caribbean.

These paths may have allowed animals like sebecids to migrate and settle. If the other teeth found across the Caribbean also belonged to sebecids, it means these reptiles weren’t just visitors. They were long-term residents.

Land bridges reshaped ecosystems

The land bridges may have shaped island ecosystems for millions of years. Now that they’re gone, smaller animals like birds, snakes, and native crocodiles have taken their place.

“You wouldn’t have been able to predict this looking at the modern ecosystem,” said a paleontologist from the Florida Museum of Natural History.

“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.”

Fossil secrets of the Caribbean

Scientists often describe islands as natural museums. Their isolation makes them safe places for rare plants and animals to hang on after they’ve vanished elsewhere. But the Caribbean still holds many sebecid secrets – especially from deep in the past.

Until now, most Caribbean fossils have been found in caves and water-filled sinkholes called blue holes. Caves protect bones from the elements, while blue holes prevent decay by cutting off oxygen.

These places have been valuable but only give a narrow view into recent biodiversity. They don’t tell us much about ancient species like sebecids.

Today, researchers are switching tactics. Instead of relying on caves and sinkholes, they’re going after older fossils in harder-to-reach spots.

“This is like a renaissance,” said Viñola-Lopez, describing the new wave of excitement in Caribbean paleontology.

Vanishing fossil sites

In the Caribbean, fossil sites vanish quickly. Rain, wind, and forests erase rocky outcrops fast. When workers cut new roads or dig into hills, researchers have to act fast.

That’s how the sebecid fossils were found. Road work in the Dominican Republic exposed the fossil bed just in time.

A graduate student from the University of Puerto Rico in Mayagüez was studying the rocks in the area and spotted the site. He notified his colleagues, and soon after, the team from the University of Florida arrived to excavate the bones.

More surprises to come

The sebecid fossils are only one piece of a much larger puzzle. In recent years, researchers have also found the first signs of mosasaurs – massive sea reptiles – in the Caribbean.

The experts have identified the region’s oldest ground sloth fossils. And new work is hinting that early human arrival may have led to the extinction of native rodents.

It’s clear there’s more to uncover. “The sebecid is only the tip of the iceberg,” said Viñola-Lopez. And with more eyes now turned to the Caribbean, who knows what ancient giants might turn up next?

The full study was published in the journal Proceedings of the Royal Society B Biological Sciences.

Image Credit: Illustration by Jorge Machuky

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