Thanks to Skillshare for supporting this episode
of SciShow. [♩INTRO] Over the years, scientists have found evidence
for a lot of weird prehistoric animals, but some of the
strangest have been crocodyliformes. These animals belong to a group that’s existed
for millions of years and that today includes modern crocodiles. We’ll call these animals “crocs” for
short, since “crocodyliformes” is kind of a mouthful. But some of these things were super weird. Modern crocodiles might seem to follow roughly
the same body plan, but some of their prehistoric relatives look
strangely like other animals. We’re talking duck croc, rat croc, pug croc,
and cat croc. These adaptations weren’t totally random,
though: Many of them are examples of convergent evolution. Basically, this is where traits are so useful
that they show up again and again, in animals that are not closely related. Like, bats and birds are not closely related,
but they did converge on flight by flapping bits of their bodies around, possibly as a way to get around quickly while
avoiding predators. And crocs, too, converged on many traits that
gave them an advantage, depending on the environmental niche that
they lived in. Which is how we ended up these five very strange,
but very lovely, examples. Mourasuchus was a group of crocodyliformes
that lived in South America during the Miocene, about five to twenty-three
million years ago. During this time, the Amazon may have been
dominated by a vast wetland. And a wide variety of crocs would have called
it home. What made the Mourasuchus stand out, though,
was their heads. Scientists have identified several species
of these crocs, and each had an unusually long and broad skull. The skulls were topped with a snout that looked
kind of like a duck’s bill, and they were filled with lots of slender
little teeth. As for why… well, it’s been suggested
that these things might have actually eaten more like baleen whales than modern
crocodiles. They may have used filter-feeding to catch
their meals, engulfing water and small, aquatic prey, then straining out the
water and swallowing what was left. As for why they evolved such an odd diet,
scientists say this might have been an example of what’s known as resource partitioning. There were a lot of crocs in South America
at this time, and there’s only ever a certain amount of food to go around in any
given ecosystem. If all the crocodyliformes were out chasing
the same food, they’d be under intense competition with
each other. By specializing in only getting a certain
type of food, Mourasuchus and the other crocs might have been able to limit their
competition and carve out niches for themselves. Some would have hunted fish, and others might
have specialized in hard-shelled prey like crabs, while Mourasuchus filtered
their food from the water. Granted, the filter-feeding idea is a hypothesis,
and not everyone agrees on it. But since scientists have found at least one
other crocodyliform that might have also been a filter feeder, it’s probably
not, outlandish. During the Cretaceous, from 144 million years
ago to 65 million years ago, North Africa was a rich ecosystem full of
lakes and rivers and animals. It was also home to a wide array of crocodyliformes, just like South America was millions of years
later. And some of them, like Kaprosuchus saharicus, took the need to diversify to terrifying extremes. Kaprosuchus, nicknamed the “boar croc”
for its tusk-like teeth, might have looked kind of like a cross between a crocodile and
a wolf or big cat, like a leopard. It was six meters long, had forward-facing
eyes like a predatory cat, and had big, muscular jaws that came equipped with three
sets of long, sharp teeth. Its nose might have also sported a keratin-reinforced
shield that could be used like a battering ram. Basically, its entire snout was potentially
built for high-impact hunting. And although we’ve only ever found its skull,
the scientists who discovered it suggest that Kaprosuchus might have even held
its legs beneath its body, instead of splayed out like a modern croc. That would have made it more agile on land. The reason this thing shared so many features
with land predators is that, like, it may have actually hunted on land, maybe
tackling big terrestrial prey like dinosaurs. These new features were biological responses
to the challenges of this lifestyle. The forward facing eyes, for example, might
have evolved to help it judge distances more precisely or see through camouflage
better. Modern crocodiles are ambush predators, so
their eyes are on the top of their head to help them watch for prey as they float
in the water. Different niches require different strategies. While Kaprosuchus might have been the most
intimidating crocodyliform to make the jump to land, at least partially, it was
far from the only one. The same expedition that discovered it also
found a bunch of other weird crocodyliformes, including the “dog croc”,
which might have had a soft, dog-like nose, and the “rat croc”,
which was tiny and had buck teeth. The most striking land-dweller, though, may
have been Armadillosuchus arrudai. Found in Brazil during the Cretaceous, it
really lived up to its name. All modern crocs have armor in the form of
osteoderms, which are small bony deposits in the skin. But Armadillosuchus took this a step further. It grew a full set of rigid body armor separated
into mobile bands, like a modern armadillo. It also had big claws and robust shoulder
bones, which suggest it might have actually been able to dig or burrow, again,
kind of like an armadillo. The area it lived in at the time was a hot,
semi-arid environment, so these big claws might have helped it dig up food or
scavenge for dead animals. This could have also enabled Armadillosuchus
to be an omnivore. This was a relatively open niche that mammals, which were somewhat rare at the time, had
not yet filled up. As for why it evolved such strong armor, we
can’t say for sure, but, well, it wasn’t the only crocodyliform
in the area. Fossils of Armadillosuchus have often been
found near big predatory crocodyliformes known as Baurusuchus. So like a modern armadillo, the extra armor
could have helped it ward off predators that maybe it was somewhat closely
related to. After all, just because you’re a croc, doesn’t mean you’re always at the top
of the croc food chain. Of course, some crocodyliformes didn’t take
to land. Instead, they doubled down on hunting in the
water. Pelagosaurus typus, for example, was an ocean-going
crocodyliform that lived during the Jurassic, about 180
million years ago. It lived in shallow, near-shore seas that
covered what is today Western Europe. One of the things that really sticks out about
Pelagosaurus is its snout. It’s super long and thin, similar to modern
gharials. And, actually, this super-skinny skull shape
has cropped up a bunch of different times before in distantly related crocodyliform
species. So scientists think this is another example
of convergent evolution, this time as a special adaptation for catching
fish. Having a slender snout limits how hard a creature
can bite down on prey, so if you’re trying to snag something big
and tough, a skinny snout would be a bad idea. But the trade-off is that a skinny snout can
move through the water much faster, letting you swipe your head back and forth
much quicker. So if your diet is agile, but relatively small
and soft, like, say, a fish, that might be a worthwhile trade-off. And we know that Pelagosaurus hunted fish. One fossil was actually found with an early
bony fish in its stomach. But though Pelagosaurus’ adaptations may
have been the result of taking to the ocean, there were crocodyliformes that took
the body changes even further. Our last example of a weird croc is a group
called the metriorhynchids. These might have had the most extreme changes
to their body plan and some of the clearest examples of convergent evolution. As the metriorhynchids’ ancestors adapted
to a life at sea, their limbs became Paddle-shaped, like a manatee, while their
tails grew shark-like flukes. They also lost the typical crocodylomorphs’
signature armor in favor of streamlined skin, like a dolphin or seal. These adaptations would have helped them maneuver
through the water. A streamlined body shape helps reduce drag,
for instance. This would have made it easier and less energy-intensive
for them to move around. They also developed glands that excrete salt,
like the ones that sea turtles have. Ingesting too much salt is harmful and even
potentially fatal for most life, but if you live in the ocean, it can be hard
to avoid that. So by developing a special gland to rid themselves
of the excess, metriorhynchids could eat salty sea life or
swallow water without getting sick. All of these adaptations were in response
to them going from land into the ocean. After examining the animals’ hips, scientists
have even suggested that they adapted to giving live birth, which would
have let them avoid having to come out of the water to lay eggs. Metriorhynchids were very successful in their
time, with lots of different species and wide ranges. Fossils have been found from South America
to Europe, from the middle Jurassic all the way up to the early Cretaceous, when
they disappeared, possibly due to shifting sea levels. It’s really striking just how often we see
convergent evolution occurring among the crocodyliformes, from to adapting to life
at sea to developing armadillo-like armor to protect yourself from other crocs. This lineage is diverse and surprising, full
of oddities and off-shoots. And whether adapting to new habitats, finding
the right niche or food supply, or avoiding getting eaten, the crocodyliformes
provide some amazing examples of how similar patterns emerge to combat similar
problems. These animals are also just really cool to
look at, or at least, the artists’ interpretations
of them are. And if looking at all these pictures is making
you wish you were better at illustrating, well, there’s a Skillshare class for that! It’s about mastering the basics of Adobe
Illustrator and is taught by an artist named Julian Burford. He won’t teach you how to illustrate crocs, but he will teach you all the basics you need
to get started. Once you’re done, you could also check out
one of Skillshare’s other classes. They have more than 25,000 of them, and with
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