How Crocodiles Escaped Mass Extinction — Twice

And what their survival story can teach us today

I still remember my first time holding a fossil crocodylomorph skull in my hands. It was smaller than I expected — no bigger than a loaf of bread — and nothing like the scary reptiles that lurk in today’s rivers and swamps (skulls can be so deceiving!). But there was something about its toothy grin and oddly shaped snout that made me pause. 

These weren’t just ancient crocodiles. They were survivors. And as I dug deeper into their story over the years, the word “survivors“ kept coming up.

A new study just added an exciting chapter to their tale.

Published in Palaeontology, the research by Dr. Keegan Melstrom and colleagues sheds light on how the ancestors of crocodiles and alligators survived not just one, but two of Earth’s biggest extinction events. 

But more importantly, their findings challenge the old stereotype of crocodilians as “living fossils” that avoided evolution. Instead, it turns out, their ancestors were remarkably adaptable, which might be the secret to their success.

Ancient Survivors with a Hidden Superpower

Crocodylomorphs (the larger group that includes today’s crocodiles, alligators, and gharials) have been around for over 230 million years. During that time, they lived through two of Earth’s major extinction events: the one at the end of the Triassic period, and the more famous one that wiped out the dinosaurs at the end of the Cretaceous.

What set them apart?

“Lots of groups closely related to crocodilians were more diverse, more abundant, and exhibited different ecologies, yet they all disappeared except these few generalist crocodilians alive today,” said Dr. Melstrom, the lead author.

The study found that crocodylomorphs who made it through mass extinctions were dietary generalists. In other words, they weren’t picky eaters. Whether it was bugs, small animals, fish, or plants, they could make a meal out of whatever was available. And that flexibility turned out to be life-saving.

A Closer Look at Skulls and Habits

To figure this out, the researchers examined the skulls of 99 extinct crocodylomorph species and 20 living crocodilian species. They analyzed them using geometric morphometrics (a way to study shape and structure) to look for clues about diet and habitat. They also compared these ancient creatures to modern mammals and lizards to get a sense of where they fit ecologically.

Fun fact: there used to be a freely available online course about geometric morphometrics that used my face, together with other PhD students at the time. 

It was a huge effort that involved museum collections across seven countries and four continents. But it paid off. The team discovered that crocodylomorphs used to be way more diverse than their modern descendants suggest. 

Some were aquatic predators. Others were land-dwelling herbivores. Some looked a bit like mammals. Others, more like lizards.

But across that whole range, the ones that made it through extinctions were the ones that could eat (and live) just about anywhere.

The Real Jurassic Survivors

Most people think of mass extinction survivors as furry, burrowing mammals. And they’re not wrong. But crocodylomorphs were doing something similar, in their own cold-blooded way.

At the end of the Triassic, around 201 million years ago, the world went through a major shake-up. Giant land reptiles that had dominated the scene (i.e. pseudosuchians) disappeared. But small, generalist crocodylomorphs made it through. Over the next 135 million years, they exploded into all kinds of forms, including bizarre land walkers and sleek marine hunters.

Then came the meteor and the end-Cretaceous extinction. This time, it was the semiaquatic generalists (creatures with diets and lifestyles closest to modern crocodiles) that survived. That’s why all 26 species alive today are some version of a water-loving ambush predator with a flexible appetite.

Why This Matters Now

Earth is currently facing what scientists consider a sixth mass extinction. This one’s not caused by asteroids or volcanic eruptions. It’s caused by us, humans. Habitat loss, climate change, and pollution are pushing species to the brink.

So what can crocodilians teach us?

“If people study mammals and reptiles and find the same patterns with respect to extinction survival, then we might predict that species with a generalist diet may do better,” said Dr. Randy Irmis, co-author and curator at the Natural History Museum of Utah. “That information helps us make predictions, but it’s unlikely we’ll ever be able to pick out which individual species will survive.”

Still, understanding what traits helped ancient animals make it through turbulent times might help us shape conservation strategies today. Flexibility, in diet, habitat, and behavior, seems to be a powerful asset.

It’s a useful reminder that adaptability often beats specialization in the long run.

The Grin That Outlasted Dinosaurs

The next time you see a crocodile basking on a riverbank, try to picture the long evolutionary line behind that grin. These animals aren’t just leftovers from the dinosaur age; they’re the winners of a million-year-long survival game. Their story isn’t one of stagnation, but of transformation, versatility, and quiet endurance.

They’ve outlasted meteor strikes, volcanic winters, and continental drift. Whether they’ll survive the Anthropocene depends not just on them, but on us.

Because even the best survivors need a place to live.

Published in Fossils et al. Follow to learn more about Paleontology and Evolution.

Do you want to become a writer for this Publication? Read the Submission Guidelines and fill out This Form.

Do you want to read more stories like this? You can now subscribe to my newsletter and join a community of over 11,000 Earth lovers!

I’m thrilled you’re here. Stay curious, and thank you for sharing this journey with me!

Best,

Sílvia P-M, PhD Climate Ages v