ExtinctZoo - The Largest Lake To Ever Exist

Episode Date: May 2, 2026

The great lakes are probably the most famous group of lakes in the entire world, named for their...well great size. And yet these guys are tiny compared to an ancient lake that used to exist, that wasn't just bigger than them each, but also bigger then all of them combined (80 times over).

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They don't move on. They manifest. They're not a demographic group. They're fans. Spotify advertising. You're among fans. If you take a map and draw an outline around Europe and the more eastern central portions of Asia, you'll realize something pretty interesting, which is that this region, despite being fairly

landlocked overall, has an oddly high amount of lakes. And in total, within this highlighted section, you'll find over 500,000 natural ones, making it one of the most lake-abundant regions on the planet, despite it not taking up a huge portion of the Earth's surface. And what's more is that in this area, it's not just the number of lakes which is odd, but also the amount of water held. As despite only accounting for roughly 10% of land surface, this region holds more than half of the world's total lake water. Now yes, some of this is just due to the sheer quantity of lakes, but a lot of it comes down to another thing, the Caspian Sea. Because despite the sea part of its name, the Caspian Sea is really no sea, instead actually being the world's largest lake. And it alone accounts for roughly 40% of all lake water.

And so, that's pretty impressive, no doubt. But in the grand scheme of history, it's actually not that jaw-dropping. It's not so long ago, geologically speaking, that is, in the very place it's now situated, was another lake that made the Caspian Sea look like, well, a lake. And its presence alone swallowed up much of Europe and Central Asia, being the largest lake to have ever existed. And this was the Peratethyst megallake. Thirty-four million years ago, the legacy in period had just begun, and Earth was quite different than today. And despite it being cooler than previous times, the global climate was still.

it was still warmer than the present, and the poles did not quite yet form permanent major ice caps, meaning that the global sea levels were much higher and leading to large coastal plains in multiple continents, as well as coasts, which went far deeper inland as well. However, for some areas, the effects of the higher sea level and different positions of tectonic plates had far more major ramifications than seen elsewhere, such as leading to the formations of inland seas, which in Europe was a process only intensified by the ongoing creation of the Alps. And these two factors together, ultimately resulted in the now ancient body of water, the neotethyst, having its most northern region suddenly cut off from the Mediterranean basin, and thus resulting in the first iteration of the peritethyst sea.

And yes, I did say sea, not lake, as in the early days of the peritethyst, that is what it was, having still been connected to outside oceans and periodically reconnecting with the neotethysts and its successors, such as the Indian Ocean and Mediterranean Sea. And this large body of water back then occupied a big part of Eurasia, and is believed to have covered an area greater than the Gulf of Mexico at its peak. In its positioning, the time it was formed, and the fact that it was a large body of water also resulted in the entire region, surrounding lands included, taking on a warm, humid, and subtropical climate. So, not exactly how you would currently picture Eurasia. And on top of this, the sea was also quite an unusual one, as it ended up occupying

a series of extremely deep basins, in other words, geological depressions, which had formed during the Jurassic period. This resulted in certain parts of the sea, developing into a very large, shallow coastal environments, while you then had these much deeper open environments as well. But while you may think this mix of habitats and warmer climate would lead to a thriving sea, the newly formed peritethys was in many ways a giant wet wasteland. And this mainly had to do with tectonic activity and external environmental factors, which combined, figuratively and perhaps literally, strangulated the sea, blocking the ventilation of water and causing a buildup of sediment that eventually transformed into an anoxic giant, wherein the water was depleted

of oxygen, and thus making it toxic to most organisms, while the sediment itself ended up becoming a death trap as well, trapping organic matter within. And these lethal conditions lasted for a grueling amount of time, nearly 20 million years to be exact, and kept the area fairly void of extensive marine life. Yet, the peritethyst would not stay this way, as around 15 million years ago or so, in the middle Miocene, things started to change, especially after the Bedinian flooding began, a continental-scale flood that saw marine waters transgressed through Europe and parts of Asia, which helped to ventilate the anoxic sea, turning it briefly into a bountiful subtropical body of water, where reefs and open marine environments were abundant.

And it was at this stage in the paratethysts that we also see life for the first time get a bit interesting, so you could say, with a turnover marine animals setting up shop. And this included multiple mammalian genera, such as large sirenians, like the meta-zytherium and lentiorinium, who were both more primitive members who could each crack three meters or ten feet in length. While not in the water all the time, the Rteodactylia brachiodas was also known to frequent area, having a build that indicated a mostly terrestrial life, but still possessed a few semi-aquatic traits, which implied that it did need to live in the vicinity of water to make the most of life, and probably to have life as well, if you get my drift.

Next, you also had a diverse range of prehistoric dolphins, some of which were hyper-preditorial, as well as marine-adapted crocodilians, like the gabulaeus, like the Gavulosucas, an uncomfortably large crock, which belonged to the same family as living gharials, yet was a tad bit more intimidating, given that its size could be around 10 meters or 30 feet in length. On top of its size, its mouth was also much more robust than those seen in living garrules as well, suggesting that sushi wasn't the only thing this predator was interested in, and probably to the dismay of all of their life. And speaking of sushi, fish were flourishing in the area as well,

being represented by a plethora of families, including a healthy amount of pipefish, and even sunfish, including, by the way, what is regarded as the largest ocean fish yet, the Ostermola, a big guppy that was on average the same length as the largest living mola ever recorded, as well as being even taller than it, meaning it was likely pushing nearly three tons in weight. And with fish, of course, comes sharks, which are technically also fish, and were commonplace in this time too, and greatly ranged in both size and niche, with some like Requiem sharks being on the smaller side, and then others like the, oh, you know, most infamous shark to ever exist,

the Megalodon, measuring up to 24.3 meters or 80 feet, based on a 2025 study that also reported a weight of up to 104 tons, which is, for a perspective, far heavier than the weight of even an Abrams tank. And so undoubtedly, its presence in the area had a massive impact on the entire ecosystem. And getting caught by this shark was the last thing you'd want to do here, as its massive jaws were capable of delivering catastrophic bites, to put it lightly, through hundreds of giant serrated teeth, which together could apply a force of 182,000 newtons, which is more than a enough power to literally cleave through the massive amounts of meat, blubber, and bones you'd find in fully grown whales. And so, because of its presence, along with the other sharks and

crocodilians, the peritethus sea was not exactly the body of water you'd want to find yourself in during these times. However, ironically, it also wasn't exactly a place you'd want to be if you were Megalodon either, as this open sea did not last for too long. And pretty much just one million or two million years later, the parade was rudely interrupted by the Alps and the Carpathian Mountains, which were experiencing a period of uplift and leading to the sea again, becoming more isolated. And this then resulted in a drop in sea level, which triggered a severe salinity crisis, which makes even the Dead Sea situation seem tame. And there's a reason it's called the Dead Sea, with vast evaporated beds of salt being formed,

and salt domes and diapirs forming that were large enough that they would have appeared like giant mountains of salt. And for the uninitiated, highly salty water is not great news for marine life, or really any life. leading to a local extinction of sorts, I saw many of the sea animals here dying out. Yet, as a wise man once said, nature finds a way, and this great dying would not be the end for the paratethyst's story, as funny enough, it was actually following this era of great saltiness that the Megalakes era finally began. Roughly 12 million years later, after the salinity crisis had been going on for two million years, and the late Miocene had begun, the tectonic plates were once again on the move, and a massive collision between them had taken place, uplifting land once more,

and finally cutting off the very little connection the paratethythus still had, and thus fully enclosing it in land, which rendered it a lake. However, calling it a lake is almost disrespectful, as it was a mega lake unlike no other. And as I said, it is as far as we know, the biggest lake so far in Earth's history. When it formed, it stretched out for a mind-boggling 2.8 million square kilometers, or over 1 million square miles,

making it actually larger than when it had first been created as a sea. And to really get understanding of its size, know that the Great Lakes of America combined could be laid across the top of this lake 10 times over, and still not cover it up. And when it comes to sheer volume, the numbers are even crazier, as you need to stick all the Great Lakes in it, not once, but wait for it, 80 times. Yes, all the Great Lakes 80 times over to fill it up. And at this size, it consumed major parts in multiple countries, including Austria, Bulgaria, Romania, Serbia, Ukraine, Russia, Georgia, Kazakhstan, and Turkmenistan.

And what may seem a bit counterintuitive at first is that when this body of water was cut off, it actually saw a reduction in its saltiness, partly because outlets of fresh water were now supplying it, and because of the creation of those salt formations, had to consequently rid large amounts of salt from the water. Still, though, contrary to what you might believe is possible, the peritathis was a megalake, which was not fresh water, for the most part, instead being brackish, a slightly salty, water that is a mixture of seawater and fresh, with current research estimating that it was about one-third of the saltiness of modern-day oceans. And because it was brackish, it means that this megalake was 450,000 times larger than the largest body of brackish water today, Lake Chilika.

And so combined, this great size, reduction in salinity, and the warm, stable temperatures of the waters, live quickly went from, not so much, to a full-on tantrum. And eventually the megalake gave rise to some of the most unique marine animals to have ever lived, as it acted as it acted it a bit like a water island, leading to a rare situation where in aquatic animals experience a type of insular isolation, and this extended to what are usually the largest animals of all time, whales. Now, the term whale today is basically synonymous with giant, but in the peritethyst megalake, not so much. Its closed-off nature meant that any whales that got trapped here had a lot less food to choose from, leading to them going on an unintended diet. And a diet

might be putting in lightly, as over time the whales of the perotethysts became the smallest baleen whales that we know of. One of the smaller whales was the Titanocetus, a name which doesn't fit it well, as this was a primitive cetacean that was only the size of a pygmy right whale, measuring about 6.1 meters or 20 feet, and generally being lighter than an Asian elephant. Yet, interestingly, it still ain't like a baleen whale, in other words, using filter feeding. And the crazy thing is that the titanicetus wasn't even the most extreme case, as you also had the seed of theorem, a whale whose name means whale beast, and yet it was the smallest baleen ever, being a teeny tiny creature that could be shorter than the average NBA player is tall, with the smallest complete adults

having measured two meters or six foot six feet. Yet with that said, depending on the individual, gender and species, they could also be more comparable to Titanocetus. Regardless, though, they were unarguably small, but had a proportionally oversized head and rib cage, whereas its tail took the brunt of the shortening, being relatively tiny compared to the rest of the body. Visit BetMGM Casino and check out the newest exclusive, the Price is Right Fortune Piz. BetMGM and GameSense remind you to play responsibly. 19 plus to wager. Ontario only.

Please play responsibly. If you have questions or concerns about your gambling or someone close to you, please contact connects Ontario at 1-866-531-2,600 to speak to an advisor. Free of charge. BetmGM operates pursuant to an operating agreement with Eye Gaming Ontario. And while small bailing whale may seem to completely defeat the purpose of their lifestyle, the Cetotherium and other dwarf bailings, did just find. in the paratethyst, largely thanks the massive blooms of phyto-planetan that supported many small organisms

the whale could feed on. And interestingly, these large blooms and the unique chemical makeup of the lake also led to something known as paratethyst blue, not to be confused with methylene blue. And it's hypothesized that because of this, the lake would have been an extremely bright, rich turquoise color. And personally, I find that colorful water tends to make the whole place seem a bit less scary. And while there are other ancient bodies of water that surely do have it beat in the horror department, the parataphis was still not a place to take lightly. For starters, in the early days of its creation, sharks could still be found within, including our old pal, the megalodon, who managed to persist and continued raining down terror on the inhabitants, which were now trapped within the lake.

Though this did turn out to be their last hurrah, so to speak, as relatively quickly, the changes in salinity in underlying chemistry became evidently too much to bear. And they apparently died off relatively quickly, with there being no known shark left, once the lake fully converted into a brackish region. But I will mention that some shark teeth have been found in the lake beds, suggesting possible to continue to survival, but the current consensus is that these were actually older teeth that were then just redeposited, which would certainly be a relief to the cetaceans, no doubt, and making the peritethis again a rather unusual place, being by far the biggest isolated body of water without sharks, presumably. But just because we aren't aware of any sharks

in this brackish megalake doesn't mean that there was no predators lurking around. As in their steed, something took over. Dolphins. The geological record is a bit complex and confusing when it comes to the brackish era, but certain evidence shows that Adon to Cedes, or toothed whales, were common here. Like the baline whales, many of these guys did seem to be on the smaller size, like the Heterodelphus or Kentriodon, both smaller dolphins that were roughly two meters or 6.6 feet long, and are believed to have had similar lifestyles of the still living, short-beaked common dolphin, which mainly feeds on epipalagic fish and cephalopods. Other, still unidentified toothed whales have also been found, but none seemed to have been that giant, with dwarfism

clearly had taken a toll on the cetaceans. And another mammalian group that was thriving here, but it also drank some of that shrinking juice, were seals. In light of the fewer number of predators here, they not only multiplied, but also chilled down a bit, and didn't have to worry about getting larger in size. And as a result, while seals in the region were plentiful and diverse, they were not that big, with most falling within a similar size range as gray seals. And for the most part, their overall appearances and lifestyle were quite similar to living seals as well, and they likely held a similar diet of smaller, fast prey, all of which they gobbled down with surprisingly sharp and powerful teeth, so don't let those water puppy dog eyes fool you.

Also, and fun, not-so-fun fact, their large numbers should in another way make you a bit uneasy, as historically nearly all seals contain high levels of mycoplasma bacteria within their mouths, which through contact, with their mouth, can cause seal finger, an infection that can lead to cellulitis, joint inflammation, and swelling in the bone marrow, which over time can cause the joints to become literally unmovable. Now, who knows the seals of the peritethis had this bacteria? Yet, given that ancestral forms of mycoplasma were already around 600 million years ago, I personally would not want to make that bet. Separately, on the flip side, one way these seals would have differed from their modern counterparts is in which food items they specialized in, as in this

mega lake, one food item that came up a lot more than normal were gastropods, which is just the fancy to aim for a vast and highly diverse group of mollusks. And I know what you're thinking. Boring and not fun. But in Peretethys, they were almost the entire party, as it was here that they achieved a nearly unparalleled quantity, being so abundant that you'd be hard pressed to take a step anywhere and not end up on someone's shell or slimy back.

Both the lake beds and shore of the peritethys seems to have been swamped with these guys. And over the years, thousands upon thousands of shells, and other evidence of their existence, has been found. Typically, it seems that the gastropods were quite small, and many could have fit on the tip of your finger, while the largest, found so far, were about the size of the Malaysian fire snail.

What's really interesting about these gastropods, though, is that they were literally one of a kind, showing adaptations to the unique water composition of the lake, resulting in the area having the highest endemic amount of gastropods known to any place, which also means that before the lake formed, none of these unique species existed, and that afterwards none survived.

A similar situation is also seen with the ostracods as well, which are informally known as seed shrimps, A group of tiny crustaceans, who like the gastropods, were extremely bountiful here, and became uniquely adapted to the waters, resulting in numerous endemic species in genera not seen anywhere else. And though you may not personally find these little critters all that interesting, they did play a vital part in sustaining the paratethyst, ultimately helping the other walks of life, including a type of animal you tend to see in lakes. Drum roll please. Fish. Yeah, there were fish. Shocker. And based on the fossil record,

Three of the most abundant families of fish in the paratethys were the cyprenids, gobids, and silver sides. The numerous genera from each family could be found here in great numbers. But again, similar to the other animals we talked about thus far, while their diversity was great, it does seem that they tended to stay on the smaller side. Although, there were certain species that could spawn individuals that were unusually big. And looking past the more common groups, you could also find far larger fish, including what was likely the largest fish in the entire megalake. Sturgeons.

Normally, when you think of a sturgeon, you probably don't picture a giant, but in reality, this type of fish can be among the largest in the world when you exclude sharks. And in paratethyst, this was no different, with species ranging from two meters in length, or 6.6 feet, all the way up to 7 meters or nearly 23 feet long, which is, for record, longer than the tallest recorded giraffe is tall, or great white shark, for that matter. And at this size, these sturgeons would have been over one ton in weight, and based on living sturgeons, it is believed that the sturgeons of the paratethyst would have fed on nearly everything except for cetaceans and seals, with cannibalism even being impossible occurrence given modern-day

sturgeon behavior. And while not to the same degree of size, the waters were also home to giant catfish that rivaled the size seen in the living well's catfish, the species that in some cases can break 10 feet or 3 meters, and casually weigh the same as a lioness. So to all my noodler viewers, the peritethis was the place for you. Although, anyone who might have considered swimming here should be aware that while not permanent residents, there is a chance you might have encountered the ot snake or crocodilian too. As in adjacent areas and rivers that connected to the megalake, these critters are present and might have visited from time to time. And this included the natrix, Tomistomas, medium-sized alligatoroids, and constrictor snakes like the paleo python. So, even though

the peritethyst as a megalake was fairly tame overall, all things considered, you still had to be on a bit of an edge. And speaking of edges, the coast of the peritethysts megalake was another aspect we cannot forget about, with its extensive shorelines, stretching out for tens of thousands of miles or kilometers, creating and making it apart to many different climates and biomes, which also means that a lot of animals lived on these shores. Now, most of them we can only infer lived around here through what we know about general myocene fauna at the time, but there are a few that we know for sure lived closer to the shore given located fossils, and this actually includes one of the largest land mammals ever, the dynotherium. On paper, this thing looked a lot

like a primitive elephant. And while it was a proboscidian, it was not a true elephant. Instead belonging to the separate family, the dynotherae who were differentiated by their flat skull, unique dentition, and notable downward turning tusks that were used to strip vegetation for consumption. And the dynotherium was an especially large member of this group, possessing a shoulder height of over four meters or 13 feet, while from a weight standpoint, 12-toned individuals were common, which fairly exceeds the average size seen in the current largest land mammal on earth, the African bush elephant. Additionally, in spite of their chunky size, these guys were excellent swimmers. And though it would not be frequent, rare cases of dynotherium crossing parts of the paratethys

has been speculated on, which also means there could have been the highly bizarre encounter between one of the largest land mammals ever and the smallest whale ever. The related gonfatheteries were also likely present in its frowning areas, as well as Hiperion-like horses, multiple phyleds, including saber-toothed cats, rhinoceratoids, the strange collectifers, a multitude of rodents and small carnivores, and then on top of all of that, you also had a lot of recognizable modern animals as well. So overall, it wasn't just the water itself gave way to life. The shores and environments they created boosted life as well, in helping make late Maya Senaurasia what it was.

Now, with all this said, as you all can probably tell, there is no longer a giant megalake in that spot today, meaning something pretty substantial likely happened to it, which begs the question of, what? Well, as it so turns out, being a self-contained lake put you at a greater risk of drying out, as opposed to when you're connected to the ocean. And the Peratethyst megalake unfortunately drew the short-stick in timing, as chaotic climate fluctuations were going on throughout the late Miocene, which started to put a lot of pressure on the ecosystem. And this pressure eventually turned lethal,

lethal during an event known as the Great Kersonian Dying, where in Salt made a big comeback in the Peretethys, probably because they were playing too much League of Legends, and then its water levels also lowered, with a lot of the bad carnage taking place between 9 to 7.7 million years ago, when the lake levels could have been dropping up to 250 meters or 820 feet on more than one occasion. And the Mega Lake overall saw a reduction of 70% of its surface and 30% of its total volume. Unsurprisingly, this horrific drought killed scores of its endemic wildlife, including nearly all of those that become adapted to brackish waters.

And unfortunately, this included the smallest whale of all time, as well as the numerous seals and dolphins, RIP. It was also around this time that the megalake started to officially break up, splintering into multiple different successors, such as Lake Pannonian, the Caspian Sea, and the Black Sea, with each going on developing their own unique wildlife. And interestingly enough, at the time this was happening, all three of them were lakes,

with only the last one, the Black Sea, being no longer considered a lake due to its connection with the Mediterranean that formed between 6,500 to 7,500 years ago. While then on the flip side, Lake Pinonean, longer exists, and like we established in the beginning, the Caspian Sea is now considered the largest lake on the planet. And while the disappearance of the paratethis can be viewed as a loss, some good did come out of it, as its drawing forced many animals to migrate in search of better lands, including based off of at least one hypothesis, the ancestor of modern-day elephants and giraffes,

who chose to relocate to the more calm plains of Africa at the time, and serving as an important reminder that one's loss is often than others gain. Thanks for watching, and until next time, on Extinctsiu.