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Everyone knows that the reptiles in the order Testudines, the lineage collectively known as turtles, are totally tubular. Those that don't put on colorful masks and fight crime play important roles in the ecosystems they call home.

But although they all share a recognizable body plan, individual turtle species have evolved traits that allow them to do remarkable things like survive icy water or pee out of their mouths. I guess when you've had a couple hundred million years on this planet, you've had the time to evolve all sorts of amazing abilities. Those traits, in turn, are teaching biologists how life adapts to environmental challenges and giving them greater insights into how animal bodies work.

And we think that's pretty rad. So here are 6 of our favorite bizarre turtles from around the world. Let's start our list with this lovely log!

I mean, uh, it's actually the mata mata turtle. The mata mata is a large freshwater turtle that can be found in the Amazon and Orinoco basins of South America … if you know what to look for. Despite growing to be as much as a meter long from nose to tail and weighing over 17 kilos, mata matas can be pretty hard to spot thanks to their exquisite camouflage.

Their shells or carapaces are often compared to tree bark and their necks to soggy leaves — so, an unassuming fish will swim by near what looks like a mess of plant material and boom, the mata mata has its lunch. But pulling off this disguise means the turtles have had to make significant changes in a few ways, particularly from the neck up. Part of pretending to be a rotting log means sitting still for long periods of time.

And that's where the turtle's weirdly long neck comes in. Its neck is longer than its spine, so it can keep the rest of its body still while it sticks its nose out of the water like a snorkel. Biologists have taken a lot of interest in those long necks as well as their flattened heads because they help the turtles slurp down their meals.

Thanks to some specialized muscles and bones, mata matas can create a strong vacuum when they extend their necks while quickly opening their wide mouths. And by studying the mechanics of how they eat, scientists just might learn how to engineer underwater machines that really suck but in a good way. When it comes to long necks, though, the mata mata has nothing on its cousin the eastern long-necked turtle.

It's one of several species often called snake-necked turtles because their necks are so long they make snake-like S shapes, especially when they tuck them under their shells for protection. But… that's not why they're weird. In fact, what makes them weird might not seem weird to us, but it's really weird for a turtle: they determine sex with chromosomes, kind of like we do.

You can find these turtles throughout eastern Australia in slow-moving bodies of water, like lakes and near dams. In fact, they're found in so many different aquatic habitats that they're thought to play a big role in dispersing the algal species that can grow on their shells. And part of their success as a species might be because of those sex chromosomes.

The vast majority of turtles have temperature-dependent sex determination, where an embryo develops as male or female based on the temperature it experiences during development. That temperature mostly depends on where and how the female turtle digs her nest. And it's a very useful way to determine sex when there are other reasons incubating at a certain temperature helps each sex survive better.

But it only works if the environment doesn't change too much — if temperatures creep up, for example, you're suddenly left with an entire generation of just males or just females. Eastern long-necked turtles use genetic sex determination instead — they have an XX/XY system that's kind of like ours, except that their chromosomes are much smaller. So small, in fact, that they're called micro-chromosomes, and they were only discovered recently because they couldn't be detected using traditional chromosome-visualizing methods.

Understanding why these turtles use chromosomes instead of temperature can teach biologists a lot about how different sex determination methods evolve. And, because relying on chromosomes means each generation has a roughly 50/50 split of sexes no matter what happens to the world around them, it may explain the turtles' ability to live and reproduce in such diverse habitats. It could even mean they're better equipped than other turtles for future climatic changes — though, only time will really tell if that's the case.

The leatherback sea turtle is as amazing as it is massive. So, very. Leatherbacks — a name which comes from the tough, rubbery skin on top of their shells — are the largest turtles alive today.

The biggest one ever recorded was over 3 meters long and weighed almost 1,000 kilograms. But, what's really impressive about leatherbacks is that they're everywhere — and that's probably because they're the only reptiles we know of that can stand below-freezing water temperatures. They have the widest range of any turtle, and can be found in open oceans from the chilly waters of Alaska to the Southern tip of Africa.

Most turtles would freeze to death if they attempted to swim around in those places, but leatherbacks can keep their bodies as much as 18 degrees warmer than the water they're in. And understanding how they pull that off can teach scientists a lot about keeping warm in cold environments. The turtles' massive size is certainly part of the answer, as there's less surface area for heat dispersion relative to their volume.

They also have a lot of oil in their bodies, which acts as insulation to trap any heat produced by cellular reactions. But another part of their secret is a unique network of blood vessels at the base of their limbs. Lots of animals use similar networks of blood vessels to conserve heat, allowing their extremities to be a bit cooler.

But with leatherbacks, the networks go the other way — ensuring the turtles' limbs stay warm. The researchers that discovered this in 2015 think that's because their overall warmth is dependent on the heat generated by their muscles when swimming, which requires completely functional flippers. And boy, do they swim a lot.

Studies where turtles are marked or tagged in some way have found individual leatherbacks can travel nearly 20,000 km in less than 2 years. That's like traveling from one end of the continental United States to the other seven times. And, remarkably, after all this globetrotting, females somehow find their way back the beach where they were born to lay their eggs.

They seem to keep track of where they are and where they need to go, but so far, the science behind their mad navigation skills remains a mystery. Pig-nosed turtles might have earned their name from their adorable snouts, but their claim to fame isn't their noses — it's their legs. Or, more accurately, their flippers, because they're the only freshwater turtle that has enlarged paddles for forelimbs instead of simpler, webbed feet.

The pig-nosed turtle is found in the rivers, lakes, and swamps of northern Australia and. Papua New Guinea. And as the last surviving member of it's family, it could hold clues to understanding some of the mysteries of turtle evolution — like, how the reptiles made their way into oceans.

Flippers are considered an important step towards a marine lifestyle, as they allow for faster and more efficient long-distance swimming, which matters a lot if you're swimming across oceans. But… that's not how the pig-nosed turtle uses them. Though their front flippers look like the limbs of sea turtles, they don't flap them quite the same way, so they're much slower and less efficient than their marine cousins.

But, they do something really weird with them that may explain why they exist. Bigger pig-nosed turtles will actually run along the river bottom using their hind legs while their front flippers are extended to provide stability and lift. When running this way, they can move almost as fast as their top swimming speeds.

And because they're not flapping their front limbs, bottom-running could help them quietly but quickly sneak up on prey. Some biologists think this may be how sea turtles first got their flippers, too — only later did they develop more efficient ways to use them. The Chinese softshell turtle has what sounds like a pretty gross habit: it pees out of its mouth.

Ok, it doesn't emit a stream of urine from its tongue or anything. But it does use its mouth to secrete urea — the waste product of protein breakdown that lots of animals, including other turtles, get rid of by urinating. And understanding exactly how they do this is helping scientists learn a lot more about how excretion systems work.

Herpetologists have always known the turtles have strange little projections of tissue in their mouths. They thought these were like gills and could pull oxygen from the water, letting the turtles breathe without surfacing. And, they do do that, to some extent.

But more importantly, in 2012, scientists discovered that they're covered in urea transporters — proteins normally found in kidneys — which pump urea out into the turtles' spit. Because of this, their saliva can have 250 times more urea than their blood. And it's such an efficient system that the animals secrete 50 times more urea through their mouths than the usual kidney-bladder route.

But as icky as all that sounds, it's likely what made it possible for Chinese softshell turtles to invade salty environments. These turtles hang out in brackish water — water that is a mix of salt and freshwater. And that's something most turtles can't do because making urine requires a lot of fluids.

Turtles generally can't drink tons of saltwater because their bodies don't have a great way of dealing with the salts in it. The only exceptions are sea turtles, which have evolved special glands for the task. But being able to excrete urea from their mouths means Chinese softshells don't have to drink a lot to pee, so they can hang out in saltier environments.

There is a drawback to all this, though — they don't have a great way of getting rid of their urea-laden spit if they hang out in drier places. Basically, they can't pee enough on land. That's why Chinese soft-shells don't spend a whole lot of time out of the water.

And when they do end up on land, they find whatever puddles they can, dip their heads in, and rinse the out their mouths. The Fitzroy River turtle is a freshwater turtle found — you guessed it! — in the tributaries of the Fitzroy River in Queensland, Australia. And it might seem like a pretty standard turtle at first, but it has an incredible superpower — it can stay underwater for days.

And, it turns out this turtle gets this power from its genitals. Turtles reproduce using a cloaca, a single opening which also connects to the urinary and digestive tracts. A lot goes on in there — and in some species, like the Fitzroy river turtle, that includes breathing.

Special sac-like structures in the cloaca called bursae basically act like internal gills. As the cloacal muscles contract, fresh water rushes into the bursae, allowing blood vessels in the tissue to absorb oxygen from the water. Studying these bursae and how they work can help scientists understand the physical limitations of the endangered turtles, and in turn, what habitats they need to persist.

And it could help engineers design systems that similarly pull oxygen from water to let people or the underwater vessels they travel in stay down longer. Now, lots of turtles have these cloacal breathing sacs, but Fitzroy river turtles have the best in the business. The inner surface of each sac is covered in papillae — little, branched projections of skin full of blood vessels — which increase the area for gas exchange by 16-fold.

That means the Fitzroy river turtle can take up a ton more oxygen — young turtles can get 70% or more of the oxygen they need from their cloacas, so they can stay underwater longer than other turtles. When not hibernating, turtles generally count their time underwater in minutes. The Fitzroy river turtle can swim around without surfacing for days at a time — and in cooler, oxygen-rich winter waters, they can stay down for weeks.

In a 2003 study, two of the tagged turtles stayed underwater for the entire 21-day field experiment. Which is not too bad for what's essentially genital-breathing. Or butt-breathing?

Cloacas are weird. And there you have it — six of the most wonderfully unique turtle species out there. Although, really, we could have made this list go on for days, because there are just so many amazing things that turtles do.

They started out-weirding their vertebrate kin before dinosaurs were even a thing, though now, over 60% of turtle species are threatened by extinction. But, if we don't give up on them, we can all help Keep Turtles Weird. If there's anything we can learn from these strange turtles, it's how successful you can be if you solve life's problems creatively.

And KiwiCo can help you foster that wonderful kind of out-of-the-box thinking in kids you care about. KiwiCo projects are designed to spark creativity and confidence in kids of all ages — from infants and toddlers to teenagers. The hands-on projects encourage them to become makers and idea generators by engineering novel solutions to problems.

When you subscribe to KiwiCo, you get a monthly crate which includes all the supplies needed for that month's project, detailed, easy-to-follow instructions, and an educational magazine so you learn even more about that crate's theme. All projects are designed in-house in Mountain View, California and rigorously tested by kids to ensure that they're educational and fun. We all want kids to have the confidence to find creative solutions, because there isn't one right answer to the problems that arise in life.

By bolstering kids' self-esteem and creative confidence, we empower them to change the world for the better. And right now, SciShow viewers can get their first month of any KiwiCo subscription for free! All you have to do is head on over to kiwico.com/scishow to get started. [ ♪OUTRO ].