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Sometimes, evolution repeats itself. There are some classics that you just can't go wrong with -- traits that are so effective for certain functions that they've evolved more than once.

Think bats and birds and insects all evolving wings. This process is called convergent evolution, and it can help us understand the similarities between living species that aren't closely related. But when an animal in the fossil record starts to look oddly familiar, convergent evolution can also help us look through time.

Here are five ancient animals whose similarity to living species has allowed us to learn some fascinating details about their lives. Pterosaurs -- the flying reptiles of the Mesozoic Era -- had a variety of lifestyles, and a bunch of different faces to match. But one of the absolute weirdest faces belonged to a pterosaur named Pterodaustro, which lived in Argentina over one hundred million years ago during the Early Cretaceous Period.

Its super-long, curved snout was filled with around a thousand closely-packed, needle-like teeth, all at the business end of a flying animal with an eight-foot wingspan. This odd structure might have totally thrown scientists for a loop, except it is very similar to a very familiar living animal: flamingos. Flamingos have pretty odd faces themselves.

Their long, crooked beaks are lined with thin structures called lamellae. But we can watch flamingos as they eat, so we know that these beaks are specially adapted for filter feeding. As flamingos pump water and mud through their beaks, tiny aquatic morsels get caught between the lamellae.

Pterodaustro seems equipped to do the same thing, using its narrow teeth to filter food out of water. And it's not alone. It belongs to a family of pterosaurs called ctenochasmatids, all of whom had long snouts with tiny teeth for filter-feeding.

And we don't have to guess about that -- we can look for evidence to support the idea that they were filter feeders. A study in 2019 described three coprolites -- that is, fossilized poops -- from an ancient shoreline in Poland during the Late Jurassic Period. The nearby sediment is covered in footprints thought to belong to a different species of ctenochasmatid, and the poops are the right size and shape to have been... pooped by those very reptiles.

A scan inside the coprolites revealed that they were full of tiny marine organisms called foraminifera, along with remains of little worms and crustaceans. We see this same poop composition in some modern-day flamingos. So not only did these ancient pterosaurs have familiar faces for a familiar feeding style, they even left behind familiar feces.

And just to complete this image of reptilian flamingos, the abundance of footprints in varying sizes on that shoreline is an indicator that these pterosaurs might have even in flocks.gathered And as to whether they were also pink… well, we can hope, and maybe someday we'll that, too.know Take a trip even further back in time, to the Triassic Period, over two hundred million years ago, and you might come across some reptiles that walk and act like crocodiles, but aren't. Because while early relatives of crocs had evolved, these aren't those. They are phytosaurs, and even though they're not all that closely related to crocs, the resemblance is remarkable. .

Like crocs, phytosaurs have large bodies with sprawling limbs, big powerful tails, and long snouts full of cone-shaped teeth. They even have bony armor covering their backs like crocs do. Paleontologists suspect these croc-shaped animals were living croc-like lifestyles as semi-aquatic predators, and there's evidence to back that up.

Phytosaur fossils are commonly found in ancient lake, river, or shoreline environments, and phytosaur footprints have been found on land and in water. Their eyes and nostrils even sit on top of the skull like crocs, though their eyes and nostrils are much closer together. This allows them to just wait below the surface of the water while they hid from predators or stalked prey. .

The crocodile comparison becomes even more detailed when we look at phytosaur jaws. Across phytosaur evolution, they developed multiple mouth shapes for different feeding styles, from big and wide to long and slender, just like the variety we see across modern-day crocodilians, like gators and gharials. And a 2019 study found that phytosaurs even have their own version of a crocodile's secondary palate. .

In crocs, the secondary palate is a structure that provides extra reinforcement for the skull, allowing it to resist stress during strong bites. Phytosaurs had a similar structure that strengthened the skull: the premaxillary palate. When researchers ran stress tests on models of phytosaur skulls, they found that if they removed the premaxillary palate, the skull became much weaker.

That makes phytosaurs and crocs an incredible example of convergent evolution from tip to tail, inside and out. . Our next animal is named Castorocauda lutrasimilis, and if you've taken Latin, all six of you, you might have already guessed why it's on this list. Its name means “beaver tail, similar to otters,” and it's one of the oldest known mammal cousins to have lived a semi-aquatic lifestyle.

Beavers are rodents, while otters are part of the weasel family, but Castorocauda is neither of those. . It's not even a true mammal, but a member of a group called docodontans, close cousins of mammals that lived alongside dinosaurs during the Mesozoic Era. Castorocauda was identified in 2006 from a single fossil found in Jurassic rocks in China.

The fossil is so well-preserved that it even has impressions of skin and fur, and paleontologists could tell right away that this animal was a swimmer. Its tail is long and flat, and the vertebrae inside are wide and compressed, similar to the tails of beavers and otters. Because the fossil is so detailed, paleontologists were able to identify evidence of webbing between its toes, and they could even see that the tail was partially scaly -- just like a beaver tail. .

It was certainly using its feet and tail to swim like a beaver, but it wasn't gnawing on trees. . The teeth in its mouth tell a different story of convergent evolution. They're pointy and angled backwards like a predatory seal's -- good for grabbing fish and aquatic invertebrates.

Now, even though Castorocauda is named for its similarities to beavers and otters, the best living comparison might actually be... platypuses. Yes, those animals that are so weird you wonder what evolution was thinking. Even they have parallels in the ancient world.

Not only is Castorocauda roughly platypus-sized, it also has strongly built front limbs that could have been useful for both swimming and digging. Just like platypuses. Castorocauda even has a small spur on its ankle, a feature platypuses use to defend themselves. .

It may not have been a true mammal, but Castorocauda survived in the Age of Dinosaurs using the same evolutionary innovations we still see in all kinds of aquatic mammals today. In 2017, scientists described another near-mammal fossil, this one from slightly younger sediments in China. Jurassic [MIY-oh-puh-TAY-jee-uhm] It was named Maiopatagium, and since this fossil also preserved evidence of skin and fur, paleontologists could see that the animal was surrounded by a blanket of skin.

This is an unusual feature, but once again modern-day animals reveal its purpose: gliding. A flap of skin that forms an air-catching surface actually has a name. It's called a patagium.

Bats have them, pterosaurs had them, and so do lots of gliding mammals. In fact, gliding membranes have evolved in multiple mammal groups: flying squirrels are rodents, sugar gliders are marsupials, and colugos are relatives of primates. But Maiopatagium belongs to an extinct group called haramiyidans, which -- like Castorocauda -- weren't true mammals, but mammal cousins.

Maiopatagium has skin flaps in spades: stretching from its cheeks to its wrists, its wrists to its ankles, and its ankles to its tail. It even has little hooks on its ankles for the skin to attach to, like bats do today! Modern mammalian gliders tend to be arboreal, and Maiopatagium shares some features that suggest it was, too, such as long legs and fingers.

And the structure of its hands and feet are a lot like what we see in bats and colugos, both of which have a habit of hanging upside-down from trees. And Maiopatagium isn't the only ancient glider. A decade before Maiopatagium was described, paleontologists reported an early mammal from.

China named Volaticotherium, also surrounded by skin flaps and thought to be a glider. Personal wing-suits have evolved convergently many times, not just among living mammals, but also their various extinct cousins. Some evolutionary tricks are so good they just keep coming back.

The last entry on our list is a group of ancient insects that would make any butterfly fan swoon. . They have big scaly wings with colorful eyespots, and they have long mouths perfect for sipping fluids from plants. But here's the thing -- they lived about fifty million years before butterflies existed.

Instead, these bugs are lacewings that lived in China from the Middle Jurassic to the Early. Cretaceous, between a hundred and sixty five and a hundred twenty million ago.years . Lacewings are still around today, but these butterfly lookalikes are an extinct group called Kalligrammatidae. .

And thanks to incredibly preserved fossils, we know a lot about them. Like butterflies, they had scaly wings and colorful patterns that included eyespots. From studying butterflies, we know these resemble large eyes to deter or distract predators.

And they had long, tubular mouthparts for collecting fluids from plants -- like what butterflies use to collect nectar from flowers. This suggests these insects were dealing with similar predators and food to modern-day butterflies. But this raises the question of exactly what plants they were feeding on.

The types of flowering plants that cover the planet today were very uncommon when these lacewings were around. . Paleontologists suspect that instead of drinking nectar like many modern insects, these lacewings were drinking from gymnosperm plants -- that is, plants whose seeds aren't surrounded by fruits, unlike many of our familiar plants today. Gymnosperms don't produce nectar quite like modern plants, but they do produce pollination drops, a type of secretion used to catch pollen.

What's more, pollen was found fossilized alongside some of these insects, so they were probably important pollinators in their time. These lacewings vanished around the time that flowering plants began to take over global ecosystems and gymnosperm plants declined. Later, toward the end of the Mesozoic Era, true butterflies evolved and formed their own close relationship with flowering plants, feeding on their fluids and carrying their pollen. .

Not only is this an example of convergent evolution in the body shape and lifestyles of these two groups of insects, it's also convergent evolution of an ecological relationship between plants and bugs. Evolution can be surprising and even confusing, but it has patterns and it repeats itself. Which means even the strangest of ancient ecosystems can hide something familiar, a clue from the present that's invaluable to understanding the past.

Meanwhile, someone who's helping us understand all the things is this month's President of Space, SR Foxley! . Thanks for helping us make videos, and thank you for doing it for years. You, too, could be President of Space one day by supporting SciShow on Patreon.

To get started, check out patreon.com/scishow. [ ♪ outro ].