Chapter 1: What is the main topic discussed in this episode?
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.
Chapter 2: What makes the Caspian Sea unique compared to other lakes?
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.
Chapter 3: What was the Paratethys Megalake and how did it form?
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 Paratethys Megalake.
34 million years ago, the Legocene period had just begun, and Earth was quite different than today.
Chapter 4: How did tectonic activity influence the Paratethys Megalake?
And despite it being cooler than previous times, the global climate was still warmer than the present, and the poles had not quite yet formed 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 formation 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 Neotethis, having its most northern region suddenly cut off from the Mediterranean basin, and thus resulting in the first iteration of the Paratethis Sea.
And yes, I did say sea, not lake, as in the early days of the Paratethis, that is what it was, having still been connected to outside oceans, and periodically reconnecting with the Neotethis and its successors, such as the Indian Ocean and the 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. And 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 shallow coastal environments, while you then had these much deeper open environments as well.
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Chapter 5: What types of marine life thrived in the Paratethys Megalake?
But, while you may think this mix of habitats and warmer climate would lead to a thriving sea, the newly formed Paratethys 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 peritethis 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 transgress 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 Paratethys that we also see life for the first time get a bit interesting, so you could say, with a trove of marine animals setting up shop. And this included multiple mammalian genera, such as large Cyrenians, like the Metazytherium and Lentiurenium, who were both more primitive members who could each crack 3 meters or 10 feet in length.
While not in the water all the time, the Arteodactyla brachiotis was also known to frequent the area, having a build that indicated a mostly terrestrial life, but still possessed a few semi-aquatic traits, which imply 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 hyperpredatorial, as well as marine-adapted crocodilians, like the Gavulasuchus, an uncomfortably large croc 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 gharials as well, suggesting that sushi wasn't the only thing this predator was interested in, and probably to the dismay of all other life.
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Chapter 6: How did the Paratethys Megalake impact the evolution of marine animals?
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 Ostromola, a big guppy that was on average the same length as the largest living mola ever accorded, 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 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 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 Paratethys 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's situation seem tame.
And uh, 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 that saw many of the sea animals here dying out.
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Chapter 7: What environmental changes led to the decline of the Paratethys Megalake?
Roughly 12 million years later, after the salinity crisis had been going on for 2 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 Paratethys 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 megalake 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 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 an 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 would 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 of 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 consequentially rid large amounts of salt from the water.
Still, though, contrary to what you might believe is possible, the Paratethys was a megalake which was not freshwater, 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 Chalika. And so combined, this great size, reduction in salinity, and the warm, stable temperatures of the waters, life quickly went from not so much to a full-on tantrum.
And eventually, the mega lake gave rise to some of the most unique marine animals to have ever lived, as it acted a bit like a water island, leading to a rare situation wherein 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 Paratethys megalake, not so much.
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Chapter 8: What were the consequences of the Great Chersonian Dying event?
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 you might be putting in lightly, as over time the whales of the Paratethys 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 ate like a baleen whale, in other words, using filter feeding.
And the crazy thing is that the Titanocetus wasn't even the most extreme case, as you also had the Cetatherium, 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 adult having measured 2 meters or 6 foot 6 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 ribcage, whereas its tail took the brunt of the shortening, being relatively tiny compared to the rest of the body.
And while a small baleen whale may seem to completely defeat the purpose of their lifestyle, the Cetotherium and other dwarf balenes did just fine in the Paratethys, largely thanks to massive blooms of phytoplankton 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 peritethis 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 a beat in the horror department, the peritethis 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 and 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 continued 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.
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