ExtinctZoo - When Summer Lasted For 10,000,000 Years

Episode Date: December 27, 2025

Most people would take a sunny-blue day after a rainy-gloomy one any day of the week. Yet, after watching this video, you might just change your mind on that.

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When you want savings, not surprises. It matters where you stay. Hilton for the stay. My friends, have you ever heard of the age-old riddle? There's 104 days of summer vacation and school comes along just to end it, so the annual problem for our generation is finding a good way to spend it. Beautifully put, if I may say so myself. And the moral of the story is, we all love summer, the weather, the events, etc.

But eventually, like everything, it comes to an end. But what if it didn't? What if summer started one day and then just continued on forever? Well, turns out we don't have to imagine, because this actually occurred, kind of, as instead of forever it was more like 10 million years of summer, but really at that point, who's counting? Now, you might be starting to feel a bit jelly at this moment, for whoever had the luxury of experiencing never-ending warm and sun. But be careful what you wish for, because this wasn't as paradise-y as one might expect, especially seeing that this event went down during a time already kind of dubious to human life, and that was the good old Cretaceous. Now, this might confuse some people, because the Cretaceous, and even the Mesozoic as the whole, is known for having been much warmer than the present, anyways.

But during this event, things got abnormally hot even for the dinosaurs. And this strange episode of time is now referred to as the Cretaceous Thermal Maximum, or as I like to call it, the longest summer in Earth's history. And though you may think the Cretaceous is synonymous with T-Rex, this all actually went down before the Rex was even a thought in Evolution's Eye. With the beginning of this story, taking place about 100 million years ago at the onset, the late Cretaceous. And things were already quite unhinged on the planet. I mean, you had giant theropods like the Spinosaurus and Carcrodontosaurus, literally living in the exact same environment.

While just across the pond, the flipping giganodosaurus was stomping around in Argentina at the same time. And that's enough teeth for everyone, no doubt. But don't forget, that during these times, depending on where you were dropped in, you would have also needed up to worry about, Supercrocks, mega-saropods, giant ornithicians, and then, of course, the heat, which to us would have felt nigh unbearable. As 100 million years ago, the Earth was specifically in the Cennemanian stage, and temperatures were already quite high, with mid-latitude seas, cracking 31 degrees Celsius in mean temperature, or about 88 degrees Fahrenheit. So swimming in the sea would have felt like a nice indoor, slightly heated swimming pool.

And in general, global temperatures are about 10 degrees Celsius, or 18 degrees Fahrenheit warmer than current temperatures, leading to widespread tropical conditions, sprawling forests, and presumably a lot of bugs. And in the polar region, things were even warmer, in a sense, as it was about 17 degrees Celsius or 30 degrees Fahrenheit hotter than current polar conditions, meaning that in other words, walking along the beaches of Antarctica, would really just feel like taking a stroll in Switzerland. Might sound pretty picturesque, but with this heat also came much more life to Antarctica and the North Pole, meaning your walk could have been interrupted by a few rather unwelcome faces.

Here's the crazy thing, though. While unarguably warm, 100 million years ago was just the start. Basically, it was the first day before summer officially began. as something was going on, something big. Yet, you could have only felt it, not seen it, or touched it, because it was happening in the air, and it had to do with a familiar phase, CO2. I know, I know, carbon dioxide seems to pop up everywhere and in every event. But this time things were very different,

as the atmosphere is based on becoming a soup of this stuff. And the reason for this ought to be quite strange. Now, normally you wouldn't expect water to ever be the culprit for a rise in carbon dioxide. But it was in the late Cretaceous, kind of. And there was specifically one body of water to blow. flame. The Atlantic. The Atlantic today is Earth's second largest ocean, stretching 4,830 kilometers or 3,000 miles at its widest point, and being large enough to cover literally 17% of all of Earth's surface. So it's hard to imagine that at one point, it was smaller, much smaller. And in fact,

180 million years ago, it didn't even exist. But this all started to change when the supercontinent of Pangaea started to break apart, and the space in between Europe, North America, Africa, and South America rifted. And in the space they left behind, water seeped in, creating the Atlantic Ocean. And while the process of its birth was stretched over millions and millions of years, it was still rather violent, in a sense, as its opening led to massive surges and earthquakes and underwater volcanism, drastically raising carbon dioxide levels, especially as the Sondamanian was coming to a close.

On top of this, the formation of the Atlantic led to an increase in worldwide sea levels. And when sea levels rise, the amount of land decreases, thus lowering the amount of forest and trees the planet could produce, and therefore causing even higher levels of carbon dioxide. And then, on top of all of this, the birth of the ocean also formed a brand new gateway that fundamentally changed the way heat was transported throughout the world, and made the oceans more sluggish, if you will, allowing for greater amounts of heat and carbon dioxide to become trapped, which all eventually had the effect of causing the atmosphere to become a thick soup of this stuff, that reached its peak during the Toronian stage, which began roughly 94 million years ago.

And so now, at this point, you could say that we had a fish, entered the most brutal months of summer. Just in this case, the time scale is in weeks, but rather millions of years. And it's estimated that carbon dioxide could have cracked 2,000 parts per million during this time, which sure is just a random number to you, but for context, that is seven times greater than the levels of pre-industrial carbon dioxide, and really is one of the highest concentrations in Earth's history, leading to the days getting longer, or at least it would have felt like that because it just got cruelly hot. So I'm sure every day felt incredibly drawn out. I mean, we're looking at days where the average temperature seen in mid-latitude

seas was about 38 degrees Celsius or 100 degrees Fahrenheit, and that's just the average. And this is 14 degrees Celsius higher than current high averages, making this Earth's hottest no point in the last 200 million years. And as a result, even traveling to certain parts of Russia and Canada would present you with tropical conditions, while the poles themselves actually maintained warm-tempered climates. But if you did insist on time traveling back here, I'd recommend that on top of packing a fan to visit most places, and also say you should watch another one of my videos as a bit of a guide. As similar to the Carnian pluvial event,

it appears that the Cretaceous thermal maximum had impacts on the hydrological system, which in this case resulted in the weather basically amplifying, meaning where it was humid, things just got more wet and rainier, whereas dry areas became even more desolate than before. And something besides weather that was also a lot more extreme during the Taronian was simply geography, as the world was doing some trippy stuff. As briefly mentioned before, the sea levels had risen during this prolonged summer, but I may have been underplaying just how severe the situation really was,

as it was in this stage that sea levels possibly reached the highest ever, with water being as high as 300 meters, were nearly 1,000 feet more than the present. In other words, over five times greater than the height of the leaning tower of Pisa. And if something like that happened today, the world would look a bit like this, and humanity would be a herding. This astronomical difference in sea level, coupled with the position of Earth's cectonic place, led to what I call fractured Earth, which I don't think it's too hard to see when taking a look at this map, with the seas and oceans essentially marooning many parts of Earth,

and creating various large inland seas that submerged much of the coasts and divided continents. Now, this abundance of warm tropical seas and waters might get you thinking that maybe it's a better idea to man up and just face the dinosaurs of the Taronian. In other words, there ain't no way we should get in the water. But in reality, for a short time during the summer stint, you could actually say the world became slightly safer to be chilling in the water than on land. I know, not the usual. As it turns out that a summer on roids and a bunch of carbon dioxide, along with the changes to the ocean circulations, isn't exactly the best thing for marine life.

You may be surprised to hear this, but we might actually have this event to think that the lack of certain monstrosities in the water, as there were two very iconic groups of marine reptiles that had trouble enduring this megasummer. The first group being the Incteosaurs, in order of marine reptiles who have been a staple within Mesozoic oceans for hundreds of millions of years, possibly even appearing before the Mesozoic during the Permian. And on average, these creatures were often dolphin-like in appearance, but were obviously not their ancestors, being rather very unrelated reptiles.

But like dolphins, they were hugely successful all over the world, expanding in just about every niche possible, while also hitting most size achievements too, with some being tiny and others being on the scale of large whales. Yet size could not save them this time, as the changing climate and oceans led to a monumental fall-off for this order, as the shift in underwater environments proved catastrophic, which was definitely not helped by the fact that the ichthyosaurus were already struggling a bit beforehand,

having already hit a plateau in diversity. And by the end of the summer, a 150 million-year-old rain had ended. And like I said, they were not the only icons to get permanently erased during the summer days. As another ill-fated group were arguably even more iconic during the later Mesozoic, and had been the undisputed apex predators of the oceans, the pliosaurs. Now these guys were essentially living swimming giant rowboats, except with massive skulls filled with some of the gnarliest teeth you could find on the entire planet. And for millions of years, they had some of the most efficient killers ever seen, being

capable of taking out just about anything that they caught, and were in fact so dominating that they even restricted the success of what we now consider the scariest animals in the ocean. Sharks. But just like the ectheosaurs, it seems like too much summer wasn't all too great for the pliosaurs, and they slowly withered as a group, becoming less diverse and smaller and smaller, until there were simply none left, possibly a combination of the changing ecosystems, and maybe the fact that one of their main food sources, the ichthyosaurs, were obviously going extinct as well.

But before you grab your swimsuits and take a jump into these warm waters, expecting it to be completely safe, I must warn you, because the Cretaceous thermal maximum may have burnt some marine animals, no pun intended, but it failed to phase others. In fact, one group of thlasophobia-inducing creatures may even have this event to think for their eventual comeback, and that would of course be the sharks I just mentioned. It may be hard to imagine this because of how scary they are now, but at one point, namely before the thermal maximum, this lot hadn't been doing too well, bowing down to not only the

pliosaurs, but also others. Yet, the long summer lended them a merciful hand, reducing competition and therefore increasing their overall diversity. And unfortunately, it also seems like sharks were seriously hitting the gym at this point, too, bulking up to size of the size of the same. not seen in close to 100 million years before the Cretaceous. And this in turn led to things like the Cardiabiodon, a type of mackle shark that prowled the waters near and around Australia, North America, England, and Kazakhstan. And it was probably one of the first sharks become an apex predator in those days.

And fully matured individuals would have reached up to 5.5 meters or 18 feet in length, similar to a large great white. And not only was it similar in size, it actually kind of looked like one too, possessing a similar body shape, with the main difference being that it had a stubbier head and different. teeth, which, by the way, were still very, very lethal, being razor sharp and robust, which is believed to have allowed it to tackle range of plesosaurs and other marine reptiles. Ironically, though, while swimming into the sky would spell trouble, it wasn't actually

the biggest fry around. No, that's how it went to the cretidus, a relatively unknown shark that was actually one of the largest to have ever lived, period. Found within the western interior seaway in various parts of Africa, Europe, and Asia, this fish was also a mackerel shark, albeit one very big mackle shark. As in some cases, it could reach up to 11.28 meters or 37 feet long, while weighing multiple tons. So at the very least, this thing would have appeared bigger than a whale shark, and it was absolutely meaner than one too, having not only blade-like teeth but a body plan akin to that of a tiger shark, with a sole differentiator, besides the overall size, being a much larger head, relatively speaking, as well as some absolutely ridiculous jaws,

which allowed it to eat other giants. and in some cases armored prey, such as marine turtles, that were even found in one specimen's stomach. And actually, speaking of turtles, this seems to be another group that benefited from the thermal maximum, leading to multiple species whose shells alone were longer than the average NBA player. And stepping back into the flasophobia area once more, we absolutely cannot forget the Cotoxirina, a legendary menace of the Western Interior Seaway that popped up around this time as well. And then we also have the less scary, but more off-putting, Aquila Lama, which was also a shark, even though yes that's

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That aided in underwater propulsion Don't worry too much though Because while coming face-to-face as one of these guys would surely be shocking It would not be that interested in you As it had quite the odd face structure Which seemed much better gulping down plankton than tearing flesh off a megafauna.

Though, I do admit that seeing one of these guys would certainly be unsettling, and probably bad for my heart. So yeah, overall, while this event did get rid of some thylastophobia-inducing creatures, it did add quite a few new ones, and this unfortunately for any scuba divers was not limited to sharks, as another group that seemingly got a major boost

for the mosasaurus. Now, these guys need no introduction, being just about the most iconic group of marine reptiles from the entire Cretaceous, and it's actually here that they got their start, or at least might have. As in the wake of the ichthyosaurs and pliosaurus, taking a monumental beating, the mosasaurus seemed to have heavily diversified and radiated, with actually the oldest fossils classified

of this family, having come straight from the Taronian. But unlike some groups, it wouldn't take these guys a long time to get moving, and during the Cretaceous thermal maximum, you would have already needed to watch out for multiple early mosasaurus. Some would have been able to nibble on you with the tiny dallosaurus, or slightly larger, cerebosaurus, but then there were a few that could have actually caused some serious damage, Like, for example, the Tethosaurus, a member that was about as long as a bull shark, and that a mouth filled with nasty, nasty teeth.

And though it was indeed a mosaura, you might have mistaken it for an oversized, hungry, strange comodo dragon, given its limbs. Not as if it would really make a difference, though, in terms of what would happen if you swim into one. However, while this guy was certainly scary, we are still in the minor leagues, so you could say, as there was also the Jaguarosaurus and Anglosaurus, two mosasaurus that cracked three meters were 10 feet long. And actually, the Agorosaurus, based on recent finds, might have even measured a massive 9 meters or nearly 30 feet, a whole lot of reptile.

But before you freak out too much, you can take solace in the fact that it did have quite an agile and slender build, compared to later Mosasaurus a similar length. Now, that said, there was one last guy on the scene that was definitely not slender, and likely the world's earliest drive Mosasaur, and that was the Tylosaurus. I know you're not expecting that guy, seeing that we usually think of this thing as living alongside than Mosasaurus much later on. But yes, in the western interior seaway, you could have seen this guy during the Tironian.

Although, while Tilosaurus would one day become one of the largest marine predators of the entire Cretaceous, it did remain in the smaller size during the Taronian, as their earliest species were about 23 feet long, as opposed to later ones, which might have reached nearly double the size. However, these first thylosaurs were still much more robust than the Aguarsaurus, allowing them to hunt a large range of prey,

including many things, by the way, which were much larger than us. So watch out. But like I said, while the waters of this time did have some questionable creatures, I'd still have picked it over the land, as green just meant many more problems than blue. For starters, on land, the oppressive heat would have felt a lot more uncomfortable. And then, of course, you also had the dinosaurs, lots and lots of them. In opposed to the waters, we didn't see that much extinction in dinosaurs or other terrestrial

animals during the thermal maximum. Rather, the event just caused more of a shake-up. A shake-up that you could argue may dinosaurs even mightier than previously. To be exact, the increase in temperature and shifting climate led to an overhaul land environment, with Savannah's becoming more common, while flora seemingly diversified in large parts thanks to the higher levels of CO2. And who likes bigger trees? Simple, big animals that like to munch on set trees. And what group of animals already has a lot of big plant lovers? Yep, you guessed it, the dinosaurs.

And of all the groups, it was of course the saropods who were the largest. Prior to this monumental summer, Sarapods were already doing pretty well, being found across the globe and achieving massive sizes. I mean, just look at the 31-meter or 102-feet-long Patigo Titan that lived in South America during the Aptian stage and could have weighed up to 57 tons, meaning you could fit over seven fully grown elephants into just one of them, one. However, things got even crazier after the thermal maximum hit, with Sarapod diversity ballooning, especially in latitudes below the equator. And interestingly enough, their average sizes reached a breaking point, perhaps thanks to all the oversized trees, which in turn ultimately gave us what is for now considered the largest dinosaur of all time, and the biggest thing to have ever walked the planet, the Argentinosaurs.

Saying this thing would have been a sight for sore eyes is putting it lightly, no pun intended. And given its name, you can tell that it would be in Argentina where you found this behemoth of an animal. For now, it's believed that the adults of this genera could have reached a whopping 80 tons, and 36 meters or 118 feet long. And this, my friends, is the estimate based on uncontroversial and substantial evidence, meaning that there are actually higher estimates out there that come from more fragmentary remains. But let me tell you, even at this quote-unquote conservative size, 80 tons is still absolutely absurd.

That's like two tanks stuffed into one living creature, a creature that has somehow maintained its ability to walk. Or another way to think about it is that the Dipodocus is one of the most famous saropods ever, and obviously a giant. And yet was still such a small fry compared to the Argentinosaurus that you could have fit six of them into just one Argentinosaurus. Now, imagine a whole herd of them stomping around. Yeah, it would have been literally insane and they absolutely had a massive role in actually shaping their ecosystem, just like elephant herds do today, except on a much, much bigger scale.

However, ultimately, while the largest, the Argentinosaurus was just one of numerous staropods that occupied the planet and benefited from the thermal maximum, with multiple being known from Australia, Asia, and others that lived alongside the Argentinosaurus in South America. Yet, admittedly, none really came close to rivaling the sky in size, but overall, still a good time to be a sarapod, and like I said, the diversity shot through the roof. But with that said, some bad news tied to this was that their increase in diversity also increased the diversity of what might have eaten saropods, in other words, theropods, as they too experience an increase in diversity in lower latitudes.

resulting in some pretty ferocious faces. I mean, just in Argentina alone, there was not just one, but three very large theropods that stocked a lance, all being Carcordontosaurus, a vicious family of theropods with unusually very sharp highly serrated teeth that could cause catastrophic bleeding and tissue damage.

And the three defined genera that I'm referring to was the Maposaurus, Maraxes, and Taravonator, all being well over four tons, and making each of them more than four times the size of the maximum recorded. polar bear. And that's just the minimum, as the Mappasaurus and Taravanator could both be closer to 6 tons and measure 12.6 meters or 41 feet long, making them both among the largest theropods ever discovered. And it was these guys that might have been the hunters of the largest

animals to ever walk, even possibly in some cases utilizing pack hunting, as there has been some evidence of large Carcrodontas swords being excavated in multiple numbers. Although, even if this was the case, researchers still think that a healthy, fully adult Argentinosaurus was probably too much of a a mouthful for any predator. One thing I can say for sure, though, is that I would not want to be around any of these guys, and by extension, prehistoric Argentina. And that's all before considering the fact that there was still a plethora of other theropods that would have absolutely loved to snack on you.

And this included a six-meter or 20-foot-long Megaraptor in, dubbed the Aonaraptor. And by now you should know that this fell trouble, as this kind of theropod killed in just about the worst way possible, likely skewering prey with their massive frontal claws and then eating it like a shish kebab. And given its size, it definitely had no problem in lifting up human-sized creatures. To go along with this, ablisor sort seemed to be thriving in the area as well, being represented by three different kinds. Atralcosaurus, Elocalacia, and Scorpiovinator.

And get this, all three of these ablosaurs were similar in size to the Megaraptorin, being about 20 feet or 6 meters long, but were a bit lighter, coming in just under one ton. And they also, of course, lack those giant arms and claws, instead actually having what looked like sausages for hands. But before you dare laugh at them, keep in mind you do not need arms to be highly lethal, and each possessed a robust shortened head that is attached to powerful neck muscles and adorned with wrinkled and serrated teeth, which all combined resulted in a very effective bite and hole tactic,

which they used to subdue prey, with some studies even suggesting that this family evolved their odd shapes and traits, partly due to specializing in hunting saropods. And they, along with the Carcordontas swords, do seem to have been the trendy theropods during the summer stint. being found in most locations even outside of South America. Yet, thankfully their size and diversity, just like the Sarapods, was a bit lessened once you let the continent, possibly the result of South America's specific latitude. However, what did seem to be missing from the South that was thriving elsewhere was two other groups of theropods, strange ones at that, as I am talking about therazenosaurs and

ovaraptorans. Now, both groups had already long existed by this point, but each experienced the boost of sorts during the Taronian. For the Therazenosaurs, this is mainly reflected to the number of existing genera, with multiple kinds living at the same time, including the Nothronikis and Segnosaurus. It was actually a rather large therzinosaur that could crack four metric tons, making it larger than even Allsaurus. But no need to worry too much, as these guys were pretty friendly. Well, at least in the sense that they were herbivores based on the shape of their teeth. It might have instead used their large claws for raking leaves, display, or perhaps defense, but definitely not for hunting.

Meanwhile, the ovoraptorans got sizey too, and in a way, even more so, as opposed to the therazenosaurs, it was during the Cretaceous Thermal Maximum that we actually got the largest overraptorine of all time, a genus who was aptly named the Gigantoraptor. Now, this theropod was essentially an oversized ostrich, which you might have run into if you traveled to Tironi, Mongolia, which at the time was a mix of very humid forests and floodplanes, plus some pockets and more semi-arid environments. And it was here that the Gigantoraptor resided, and what was interesting about this guy, is that while it wasn't larger than, say, the Segnosaurus, it was crazily massive for

an ovirapturin, with the largest specimens measuring 26 feet were 8 meters long, and standing 3.5 meters or 11 feet tall at the hip, making them about as tall as a giraffe, but much heftier, weighing about 8 tons. So basically the equivalent of 8 ostriches. And this is super nutty, because the next largest of its kind, though we know of, is literally 35 times smaller. So obviously that vitamin D seemed to be doing something. But then it also leads to the more serious question of what changes when an overraptor blows up this much? And the answer is unsurprisingly, diet and lifestyle changes. As of all the kinds of overraptors, the giganticaraptor had by far the deepest beak and the sharpest shelves in terms of its dentory, meaning that could technically

have processed both plant material and meat. And then when you add in the fact that given its large size and therefore high energy needs, it's presumed that this guy would have actually been an omnivore that specifically was more generalistic in nature, eating just about whatever it could take down, moving or not. Which played quite a very. well into its environments, seeing that the environments was, like I said, a mix of different biomes, and therefore there could have been many different snacks to choose from. So overall, clearly, theropods did quite well for themselves during the thermal maximum, and even tyrannosaurids could be found worldwide, although at this time they did remain

mainly small predators, for the time being. However, we can't forget that along with staropods and theropods, you also had ornithicians. I mean, these guys were everywhere, and they too were majorly impacted by the new heat and changes the world saw. Now, what is quite interesting about them is that while theropods did see increased diversity where saropods were found, it was actually with Ornithysians that thereopods had had even stronger correlation, especially in the northern hemisphere, where both groups had massive spikes in the number of species, whereas saropods did weaker appear. In the case of the Ornithicians, this resulted in a plethora of new encalosaurs, serotopsians,

and of course hadrosaers sprouting up. Asia in particular seemed to be quite the hotspot, no pun intended. And we see that within the gigantic reptor's environment and surrounding areas that a multitude of other dinosaurs lived, such as the Bactosaurus, Gimoriosaurus, and while in China, multiple in Kallosaurus and seratops were found, similar to the situation in North America. And so overall, I think it's pretty safe to say that this extended summer ended up playing a huge role in the evolution of dinosaurs, and really life on Earth in general. So the next time that you hope summer never ends, maybe ponder if that's really what you want. Thanks for watching, and until next time, on you.

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