00:00This is Low Long, the largest crocodile ever found, stretching about 20 feet long.
00:07Now, imagine living in a world full of Low Longs, only with longer legs and the ability to run on land like a greyhound.
00:15It sounds like a nightmare monster, but she was real.
00:19Fossils of giant crocodile-like creatures were discovered back in the 1930s.
00:23And now, scientists have found that these beasts, once roamed and dominated, lands far bigger than they imagined.
00:31We're talking about the Cebacids.
00:33They're a family of prehistoric crocodiles that once ruled South America, especially in what is now Argentina, Brazil, and Bolivia.
00:41And scientists discovered that these ancient predators were huge!
00:45Some species may have grown up to 20 feet long.
00:48Now, to give you an idea of how big that is, well, that would be you.
00:52And that would be her.
00:55Yeah, good luck outrunning that.
00:57Oh, by the way, they wouldn't be slithering in the water.
00:59They'd be walking right beside you.
01:02And that's actually the biggest difference between them and their crocodile relatives.
01:06Most Cebacid species lived entirely on land.
01:09They were like lions.
01:11Powerful, moving on all fours, but with tough crocodile-like skin.
01:15That image alone is already terrifying.
01:17But it gets worse when you figure these guys were fierce predators and we could have easily ended up as part of their dinner.
01:25Everything about them was perfectly built for the chase.
01:28They had narrow, dinosaur-like skulls and long legs that helped them sprint after their prey.
01:34They especially liked sloths and rodents.
01:36But, honestly, with those sharp, saw-like teeth, well, anything that crossed their path didn't stand much of a chance.
01:44And if one of their victims tried to fight back, well, that would have been a big mistake.
01:49Most of these crocodile ancestor species had tough, bony plates under their skin that worked like natural armor.
01:56They were seriously tough.
01:58But don't worry, you don't have to fear them.
02:01Luckily, for us at least, these beasts aren't roaming the Earth anymore.
02:04According to Jonathan Block, a paleontologist at the Florida Museum of Natural History,
02:10these mysterious predators may have been the last of the Notosussians,
02:14a broad group of reptiles that first appeared back in the Jurassic period.
02:19Yep, these bad boys shared the planet with dinosaurs.
02:23That is, until the asteroid hit the Earth about 66 million years ago.
02:27Dinosaurs went kaput, and mammals took over.
02:30They became the land animals, but their path to the top wasn't exactly smooth.
02:35They still had to deal with the cebacids in South America.
02:39That's right, those tough, crocodile-like predators actually survived the asteroid disaster.
02:45They also ruled and stayed at the top of the food chain until around 11 million years ago.
02:50Or at least that's what scientists thought.
02:52Until they started finding strange, fossilized teeth in the Caribbean.
02:57Uh-oh.
02:58Let's go back about 30 years, when researchers uncovered two roughly 18-million-year-old teeth in Cuba.
03:06They had a tapered shape and tiny, sharp serrations, perfectly designed for tearing into meat.
03:12There was no mistake.
03:13Scientists were looking at something that belonged to a top predator.
03:17But the question was, who?
03:19Had they found a fossil of an ancient giant croc?
03:23Well, maybe.
03:24Those teeth could have been from a species of cebacid.
03:27But that was strange, since scientists didn't think such large ancient predators ever lived in the Caribbean.
03:34And things got even stranger when another tooth turned up in Puerto Rico.
03:39This one even older, about 29 million years old.
03:42But there was a problem.
03:44Those teeth alone weren't enough to identify a specific animal.
03:47They needed more.
03:49So the mystery remained unsolved.
03:53Everything changed in 2023.
03:56Local work crews were building a road in the Dominican Republic when they suddenly stumbled upon ancient bones.
04:03Researchers soon realized they were looking at a fossilized tooth.
04:07But this time, it came with two vertebrae.
04:09That was a big deal.
04:11Because it's really hard to tell ancient crocodile species apart just from their teeth.
04:16But with those two vertebrae, things were different.
04:20Crocodile relatives with serrated teeth usually had ball and socket joints between their vertebrae.
04:25But in cebacids, that part of the spine was flat.
04:29So that made all the difference.
04:31It was enough to confirm that the fossil from the Dominican Republic belonged to a cebacid.
04:36And just like that, scientists discovered that this ancient predator really did live in the Caribbean.
04:43And even more surprising, they found out it was roaming around at least 5 million years
04:48before cebacids were thought to have disappeared everywhere else.
04:52Okay, but why is finding their fossils in the Caribbean such a big deal?
04:57Or better yet, why were scientists so sure before this discovery that they didn't live there?
05:02Well, that's because this prehistoric reptile didn't like the sea.
05:07Let me explain.
05:08The Caribbean is a region in the Americas made up of islands and the surrounding coastal areas.
05:14That meant for a land-loving ancient crocodile to travel from, say, Colombia to the Dominican Republic,
05:20it would have had to swim.
05:22And I mean really swim.
05:24We're talking over 350 miles of open ocean with strong currents and rough waves.
05:30You can see why that would have been a serious challenge for a land-based cebacid to cross, right?
05:35So, that's why scientists thought these prehistoric crocodiles could never have lived in the Caribbean.
05:41But now that researchers are finding their fossils there, they may have to find an explanation.
05:47And that is where this discovery becomes even more interesting, as it actually supports the Garlandia hypothesis.
05:54This idea first appeared in 1994.
05:58It suggests that millions of years ago, the movement of Earth's tectonic plates caused a stretch of land, now mostly underwater, to rise up in the Caribbean.
06:08This land, called the Aves Ridge, may have connected South America all the way to Puerto Rico, and then to other Caribbean islands, like Hispaniola, Cuba, and Jamaica.
06:19So basically, it worked like a temporary chain of land bridges, a kind of natural highway that once allowed animals to go from South America to the Caribbean.
06:28Mammals, amphibians, and reptiles could actually walk right across instead of taking their chances at sea.
06:35The Garlandia hypothesis definitely sounds fascinating, but it's still up for debate.
06:41It hasn't been fully accepted by scientists yet, even though plenty of studies since the 90s seem to back it up.
06:47And this new discovery of a giant crocodile-like creature in the Dominican Republic could be one more important clue pointing in that direction.
06:57It's possible that many of the places where these civisids once thrived started to disappear as the global climate cooled.
07:05Bit by bit, some of them were pushed into warmer tropical areas, until, eventually, the only places left for them to live were the Caribbean islands.
07:14This discovery lines up with something else that ecologists have observed around the world.
07:20Islands can act like museums of biodiversity, in the sense that they offer a safe place where plants and animals can keep surviving long after their relatives on the mainland have disappeared.
07:32In the case of civisids, the difference is striking.
07:35The most recent fossils found in South America date back between 10 and 12 million years ago.
07:41But the tooth and vertebrae found in the Dominican Republic are much younger, only about 4.5 million years old.
07:49That means this island might have been the last place these giant reptiles called home.
07:54And if those serrated teeth found on other Caribbean islands also turned out to belong to civisids, that would be huge.
08:02That would mean that these ancient crocodile-like creatures didn't just live in the Dominican Republic.
08:07They were spread across the Caribbean.
08:10And who knows, maybe we'll still find more of its fossils in places like Puerto Rico, Haiti, and Jamaica.
08:17Although the tropics are among the most biodiverse places on Earth, much of their natural history remains a mystery.
08:24Discovering a giant ancient crocodile in the Caribbean is a reminder that the world we live in today is just one chapter of Earth's long, ever-changing history.
08:33And who knows, what other prehistoric crocodiles or ancient creatures are still waiting to be found beneath our feet.
08:45That's it for today.
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