Crocodilians do all kind of look the same.

And their lineage has existed for  hundreds of millions of years, weathering two different mass extinctions that took out the dinosaurs and  also many other species. You’d be forgiven for thinking that both of  those things were true at the same time – that crocodilians have always been short-legged, log-shaped predators lurking at the water’s edge.

But the crocs we have today are not the  same as the crocs of the distant past. And although modern crocs are great survivors, they aren’t even using the same strategies that allowed their ancestors to  survive ancient apocalypses. From armored plant-eaters  to swift two-legged hunters, here is how the crocs of the past conquered  the world and lived to tell about it. [♪ INTRO] Today’s crocodilians include crocodiles,  alligators, caimans, and gharials.

They are all large predators that find most of their food in and around shallow waters. These impressive reptiles are part of  an ancient lineage called Pseudosuchia, who got their start way  back in the Triassic Period, more than 200 million years ago. Triassic pseudosuchians were some of  the most diverse and successful animals on land, and they came in a variety that makes modern crocs look like underachievers.

There were the armored aetosaurs  which stomped around on four legs looking for plants and animals to eat,  and which could grow several meters long, every inch of which was covered  in bony armor plates and spikes. There were massive rauisuchians,  quadrupedal apex predators that hunted on land and could be  even bigger than the aetosaurs. And there were even some two-legged  carnivores like Poposaurus, which look so much like early  carnivorous dinosaurs that it took paleontologists a while to figure  out that they were actually closer to crocs.

The Triassic was a world where  crocodile-cousins competed with early dinosaurs and ancestral  mammals - and often came out on top. But the period ended with a mass  extinction, around 200 million years ago. As the supercontinent of Pangaea broke  apart, extensive volcanic activity wreaked havoc with the planet’s climate.  It was a bad time for the pseudosuchians.

The big apex predators and  plant-eaters disappeared, leaving open ecological niches that  would later be filled by dinosaurs. The only pseudosuchian survivors were  a small group called crocodylomorphs. Clearly these survivors  were doing something right, so to figure out what made them different, a 2025 study took a close  look at fossil jaws and teeth.

They compared over one hundred  species of crocs, living and extinct, from all over the world, plus a bunch  of mammals and lizards for good measure. And they found a trend: while  many species have mouths built for specialized diets of plants or prey, the Triassic survivors were all omnivores  or insectivores, and all relatively small. They were united by a lack  of dietary specialization – they were the opposite of picky eaters.

And this isn’t surprising. When the ecosystem is falling apart around you, having a refined palate is a recipe for disaster. A flexible diet is key for getting  enough food during difficult times.

And it paid off. As the Triassic gave way to the  Jurassic and then the Cretaceous, the crocodylomorphs gave rise to an even more diverse set of Mesozoic descendants. New to the scene were the notosuchians, who had short skulls that gave them a  surprisingly mammal-like appearance, and allowed them to enjoy  diets of plants and bugs.

Meanwhile, another lineage called  thalattosuchians left the land altogether, moving into the ocean and evolving large bodies and long skulls not unlike what  we would later see in whales. And then there was a group called Crocodylia, which couldn’t commit to land  or sea and instead settled into roles as semi-aquatic predators,  just like their descendants do today. All in all, the Age of Dinosaurs was  also an age of diverse ancient crocs.

Of course, you know how  the Age of Dinosaurs ended. At the close of the Cretaceous  Period, 66 million years ago, a massive object struck the Earth and  set off a global ecological disaster. And just like the last one, only  some of those crocs made it through, but they didn’t use the same strategy as before.

During the Triassic extinction, the survivors  had mainly been land-dwelling species, but in a world full of dinosaur  and mammal competition, there weren’t many crocodylomorphs that  had successfully picked up that lifestyle. So this time, the survivors  were the semi-aquatic ones. Using the same methods of comparing skulls, that study found that even though  their lifestyle was different, the Cretaceous survivors once again had jaws and teeth that allowed  for a variety of foods.

We actually see a similar life strategy today. Modern alligators and crocodiles are  really good at eating basically anything. Bugs, fish, aquatic prey, land  prey, big food and small food.

Their ancestors, the ones who survived the latest mass extinction,  shared this flexible diet. Crocs aren’t alone in this. A similar trend has been seen in mammals – species with a more generalized diet had a higher survival rate during  the Cretaceous extinction.

Now, diet isn’t everything. Crocodilians also tend to reach  sexual maturity pretty quickly, and they lay lots of eggs at a time, which means they’re good  at making more crocs fast. During a mass extinction,  rapid reproduction can mean populations bounce back and  adapt that much more effectively.

On top of that, freshwater  habitats like lakes and rivers were a good place to be during  the end-Cretaceous extinction. That’s partly because animals  could hide underwater from some of the harsh environmental changes, and partly because freshwater  ecosystems don’t just rely on plants to form the base of the food  chain, but also incorporate carcasses and other decaying matter. Once again, flexible food sources are a winner.

So when it came time to survive  the end of the Cretaceous, it was good to be a croc that lived like a croc. But the history of this group  proves that what works in one mass extinction isn’t necessarily  going to work in the next one. And that’s worth keeping in mind as  another ecological catastrophe looms.

After the Age of Dinosaurs ended,  crocs didn’t diversify like before. We got more semi-aquatic predators, and even some land-dwellers in the  form of the carnivorous sebecosuchians. But the last 60 million years  or so have been hard on crocs.

Mammals have been taking up lots of  good eco-space on land and in the sea, and the world has been gradually getting colder and thus less friendly  to cold-blooded reptiles. Today, the remaining crocs  are semi-aquatic generalists, carrying on the legacy of  their Cretaceous ancestors. This shape and lifestyle isn’t  the way crocs have always been, but it seems to be the latest winning strategy.

And now that the world is experiencing  another global ecological crisis, the future of crocs is uncertain. Thanks to human activity,  habitats are being damaged, the climate is changing, and species  are going extinct at an alarming rate. Researchers hope that by  studying crocs of the past, by learning how those ancient reptiles  endured calamities of the distant past, we might get an idea of how we can  help them survive the next one. [♪ OUTRO]