ExtinctZoo - This Prehistoric Ocean Was Thalassophobia On Steroids

Episode Date: August 13, 2024

If you thought Jaws was scary, wait until you see what prehistoric sea monsters lurked in the depths of this ocean...

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Co-Pilot handles the spreadsheets. Learn more at M365Copilot.com slash work. For many good reasons, you are probably much more willing to be dropped into the middle of nowhere on land, rather than in the ocean or sea. After all, it does appear that once you venture into the depths, life starts to become more disturbing. And this seems to be a common trend throughout history, as every point in time often has an animal or two lurking around in the waters that was far scarier than anything found on land.

One documentary that nicely sums this up is sea monsters, which made a list of the top 10 deadliest seas or oceans of all time. Among those mentioned included Jurassic waters home to giant pliosaurs, pre-Masozoic oceans filled with giant cephalopods and sea scorpions, and even a Cenozoic sea that was home to the largest shark of all time. However, all this paled in comparison to their winter, a body of water that existed during the Lake Cretaceous that was home to numerous animals that would put much of the marine predators of today to shame.

Some of these beasts were included in the documentary, yet many didn't make the cut, despite definitely being worthy of tingling your thalasophobia, and adding more reason as to why this body of water was absolutely the worst place to go swimming ever. Welcome, my friends, to the Western Interior Seaway, or as some people like to call it, Hell's Aquarium. While you may have never heard of this prehistoric shallow ocean or inland sea, there is a fair chance you've walked across it, or at least what's left of it, if you live in the United States, Mexico, or Canada. Because when it was filled with water, it split these countries across,

basically drawing a line through most of North America. And in the process, it created two island continents that no longer exist, Laramidia, which lay to the west, and Appalachia that stood to the east. This state of existence persisted for roughly 34 million years, from the early Cretaceous 100 million years ago, all the way to the earliest Paleocene epoch, 66 million years ago. Throughout this time, sea monsters could be found at every point, but some periods were unarguably worse than others,

with the Western interior seaway, having reached its climax in peak nopeness during the Campanian Age of the late Cretaceous, spanning between 83.6 and 72.1 million years ago. At the time, the seaway was warm and tropical in nature, while spanning 600 miles or 970 kilometers at its widest point. and measuring over 2,000 miles or 3,200 kilometers long. Additionally, it was remarkably shallow for its size,

possibly only being 900 meters or 3,000 feet deep at its deepest point, compared to its presumed average depth of around 50 meters or 150 feet. Yet despite its smallish size, the Western Interior Seaway still managed to cram in a ridiculous amount of nightmarish predators that were routinely larger or scarier than any of the predatory dinosaurs seen on land. By far, the most famous of these aquatic monsters, and likely the worst to swim into, were the mosasors. This was an extinct group of aquatic reptiles that could grow to massive sizes, and were characterized by body shapes similar to that of monitor lizards.

However, unlike their modern-day relatives, Mosasaurus had four paddle-like flippers instead of limbs, and their bodies were elongated and streamlined for maximum drag reduction. Depending on how advanced the said species was, these guys would have also swam like an eel in an undulating fashion, or as in later developed mosasaurus like a shark, as they had larger tail flukes that they used to repel themselves with surprising speed. These powerful swimmers completely dominated the western interior seaway, often being the biggest predators, and sporting highly specialized teeth that were typically large, sharp, and sometimes serrated. Their success ultimately resulted in them enjoying a high level of diversification that they didn't experience anywhere else,

as over 10 january are known to have coexisted all at once. ranging from 2 meters or 6.5 feet to possibly 18 meters or 59 feet in length. But despite their diversity, chances are you'd only be attacked by three kinds, the platycarpus, cladasties, and thylosaurus. As together, they represent the most abundant mosasaurus in this environment, with most specimens from this time being attributed to them. Of the trio, the smallest was Clydasties, who was still by no means tiny, with certain specimens growing up to 6.2 meters or 20 feet in length.

which is similar to the length of the largest recorded Great Whites, although it was much more narrow, which came with its own advantages as it allowed it to be an extremely agile hunter, who used its smooth teeth to catch a variety of fish and invertebrates within the shallowest parts of the seaway. While it wasn't designed to be a threat to human-sized animals per se, this mosesaur was still capable of a nasty bite, and may have even been able to travel for some time into fresh water,

making it that much harder to avoid. Things start to further ramp up when moving on to the plight, platicarpus, as this abundant mosesore was a tad bit bigger, with certain individuals measuring 24 feet or 7 meters from head to tail, while weighing about one ton, close to the weight of giant Nile Crocs, Africa's current largest predator. At this size, the platicarpus should hopefully raise your thalasophobia more than clidasties, and yet ironically, it likely wasn't a huge threat to aquatic megafauna, since studies on its teeth have found them to have been extremely fragile, leading paleontologists to speculate that a feasted primarily on smaller fish and soft-tissued squid within deep waters.

It might start looking like this was the worst place ever, solely for little critters, but don't relax too much, as the third most common mosesaur was a giant with an appetite to match, and this is the Tylosaurus. This mosesore was in most ways the same as others of its kind. Just everything about it was much bigger, with adults being anywhere from 12 to 15.8 meters or 39 to 52 feet long, fairly similar to the length of a hump of. whale and making it one of the largest mosasaurus across the entire planet. And unlike the platicarpus, Tylosaurus had teeth that were no joke,

with matured individuals possessing up to 32 teeth at any given point, that were fairly similar to each other in nature, being large, thick, recurved, and finely serrated, perfectly adapted for tearing through large animals. And thanks to its size, Tylosaurus could pretty much bully anything it wanted to in its environment, playing the role of an apex predator and routinely hunted a wide range of animals. that is reflected by its stomach contents,

as they have included the remains of plesiosaurus, turtles, birds, bony fish, sharks, and even other mosasores. The Tylosaurus is believed to have mostly utilized ambushes during these hunts, where it would strike unsuspecting prey at high speeds and possibly deploying a secret weapon as well. Its snout. This snout was quite unique to Tylosaurus,

with it being proportionally very long and having all teeth situated farther back, meaning that the front was pure bone. The tip of the snout was also fitted with a robustly built a knob that was backed by shock compression structures, leading to the belief that this snout was literally a built-in ram that Tylosaurus used to bash animals around. It evidence shows that Tylosaurus was quite liberal with the use of this weapon, being a hyper-aggressive animal that attacked nearly everything, including itself, as adult specimens routinely bear damage thought to have come from other competitors.

Even the rare yet equally deadly mosasaurus was sometimes attacked, with one fatal case even being known of, wherein a Tylosaurus had rammed and smashed the brain case of a mosasaurus apart, leading to a swift death. Don't get it twisted, though, as Mosasaurus still held the distinction of the largest Mosasaur and therefore predator in these waters, occasionally growing to be 17.1 meters or 56 feet long, and weighing over 10 tons. And while it didn't have a battering ram like Talosaurus did, Mosasaurus arguably had the deadlier bite,

with its skull being relatively large for its body, allowing for a row of giant teeth that were made for slicing and dicing. Each tooth possessed two opposite cutting edges as well as prisms that ran down the sides, helping each bite to cut deeper while simultaneously improving the overall gripping strength. Its bite was also much more powerful, with studies suggesting a bite force of between 13,000 and 16,000 pounds per square inch, which is four times the power of a saltwater crox bite. With such power and size, Mosasaurus became another one of the Western Interior Seaways apex predators, having a diet just as

diverse as the Tylosaurus. And again, similar to its relative, it is thought to have employed ambush hunting to capture prey. Unlike sharks, these giants didn't rely on a keen sense of smell to target prey. Rather, they had powerful binocular vision that provided pristine views in the murkiest of waters. And unfortunately for all, Tylosaurus and Mosasaurus were not the only giants of their kind prowling around with great vision, as you also had mosasaurus like prognathodon, which was only 25% smaller than the Mosasaurus, and also had a ferocious bite. Remarkably, despite holding the title of the biggest predators, the Mosasaurus did not have the deadliest jaws in these waters, as that title went to a predator that coasted the most outer edges of the western interior seaway, the Dinosuke.

Yep, that's right, this prehistoric body of water not only had the largest mosasaurus of all time, but one of the largest crocodilians as well. Currently, scientists are not positive on the extent of the Dinosukas' presence in the region, but it's thought that it definitely inhabited bays, estuaries, and the coast, while perhaps venturing in deeper waters as well from time to time, since specimens have been found in marine deposits. Furthermore, it definitely lived on both the eastern and western side of the seaway, and interestingly differed in size depending on which side it lived.

To the east, Dinosukas grew to smaller sizes but were far more plentiful, while in the west they were fewer but far larger, reaching 12 meters or 39 feet in length. This obviously isn't very close to the length of the largest mosasors, though Dinosuchus was far more robust and built, allowing it to stand its ground when it came to weight, with estimates suggesting a maximum of around 8.5 tons. Disregarding weight, Dinosucus had the advantage of more impregnable,

defenses, since, like many crocodilians, it too was covered in osteoderms. However, Dino-Sucas was a bit unique in that its osteoderms were much larger and heavier than normal. In fact, when they were first recovered, paleontologists confused them for the armor of an Enkylosaurus. These homegrown armored plates would have covered the back of adults and were hemispherical in shape, providing ample armor while also serving as attachment points for tissue, which ultimately played a massive role in its ability to walk outside of water. Overall, these osteoderms made dynosuchus one of the better equipped animals in the waters, but what really made it stick out was its monstrous bite.

For starters, Dinosukas had massive skulls that were alligator-like in structure, meaning they were very broad, giving them immense biting power that was only amplified by the presence of well-developed jaw muscles. All of this resulted in a bite that potentially delivered more power than even that of a fully grown T-Rex, with some studies estimating a bite force of over 100,000 Newton's, five times the power needed to crush a car. This staggering amount of energy would have been channeled into their robust teeth that were sharper towards the front and blunter towards the back, suggesting that this crock was designed to crush things to death rather than tear. It's thought that like the American alligator, Dinosukas was an opportunistic feeder who munched on anything it could catch. Yet fossil evidence shows that it had a preference for marine turtles, large fish,

and dinosaurs that ventured too close to the water. The coasts and shallow reefs of this prehistoric seaway were no doubt a terrible place to be if trying to avoid the largest predators around. But the more open waters were home to their own share of nightmares too, including rather peculiar cephalopods, to say the least. Cretaceous cephalopods, like those of today, were still found in shallow water,

but they held a much more expansive range in the deeper areas compared to others. Despite not being as big or as bad as the mosae, or Dinosuchus, for that matter, they still feasted on whatever was floating around, as Western Interior Seaway cephalopods were among the biggest of their kind, even rivaling the size of living crackens today, like the colossal and giant squid. Two of the better-known large cephalopods from those times were Tussotuthis and Ancotuthus, both members of the now-extinct Ancotuthanay family.

These two sea monsters were incredibly similar. So much so, in fact, that paleontologists often like to argue on if a recovery specimen belongs to one or the other. What we do know, though, is that they were big, frightening-looking, and confusing. Confusing in the sense that they had the appearance of a girthy, relatively short squid, and yet were more related to modern octopus than living squids. In their youth, these sepulopods were quite small and vulnerable to attacks, with paleontologists believing that they actually made up the bulk of a lot of aquatic animals' diets, an idea backed by prehistoric fish stomach contents. However, in response to being fish food,

these cephalopods adapted by maturing rapidly and showing extreme size variation among individuals, leading to some specimens being about the size of your arm, while others could get three meters or 10 feet long. Now this size, these guys were active predators and turned the tables on their once-would-be attackers, typically eating fish, invertebrates, and even vertebrates, like baby mosasors and pleasiosaurus. Akin to how octopus hunt, twosothis, and ancotuthis would have used their ten tentacles lined with suckers, to ensnare prey which were then swiftly ushered into their waiting beaks. Additionally, while not confirmed, many think that they were also capable of squirting ink when a quick escape was necessary, and were quite speedy, relying upon jet propulsion to maneuver the waters.

Obviously, these cephalopods had some useful tools, yet one area that they were lacking in was armor, as their bodies were for the most part composed of very soft tissue. Although there was another cephalopod lurking around that had an answer to this problem. This was Parapazosia. Despite hailing from the same class of animals, Parapagosia was not an octopata like the two formerly mentioned creatures, but instead a member of the Ammonite order, a now extinct group of cephalopods whose closest living relatives are the colloids.

All members of this order, parapasosia included, bore spiral shells which were made of calcium carbonate, the same mineral scene in snail shells. Analysis on the shells showed that the calcium carbonate was arranged in prisms, crystals, or other shapes and patterns, depending on the layer. These shells provided a fair degree of protection against predators, and also housed the majority of their bodies, which in the case of Parapidososia was a lot, since it was a true sea monster, holding the title of the largest known ammonite and the heaviest cephalopod

of all time, outclassing both the giant and colossal squid. The largest known Parapisosia had shells that were possibly 3.5 meters or 11 feet in diameter, meaning that with flesh, these individuals are probably over 1.5 tons in weight, of which nearly half came from the shell alone. And if you could somehow pry a shell off of one of these giants, it's thought that their body would uncurl to a total length of 60 feet or 18 meters, about twice the length of a whale shark. Such size gave Parapizosia one more accolade, the heaviest invertebrate of all time. But what it did with this size is unknown, as all members of its order and their closer relatives are extinct, rendering their daily lives a mystery.

What we do know, though, is that individuals could be found throughout the entire western interior seaway, intended to stick to the upper layer of water, typically not going below 250 meters or 800 feet, meaning that unlike giant squids of today, these behemoths weren't hard to find. And finding it may not have been in your best interest either, as it could have been adept at catching fish, other cephalopods, and even marine reptiles. However, on the flip side, some think it was actually more likely to give you a death through jump scare than predation, with some arguing that it mostly stuck to vegetation and plankton, only hunting the slowest of creatures due to its sluggishness.

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and more time actually interviewing candidates who check all your boxes. Listeners of this shell will get a $75-sponsored job credit at Indeed.com slash podcast. That's indeed.com slash podcast. Terms and conditions apply. Need a hiring hero? This is a job for Indeed sponsored jobs. It's quite shocking that this giant bizarre invertebrate could be found in the area that also housed the largest mosasaur and one of the largest crocodilians of all time, making the western interior seaway seem like something out of a monster movie. And at the very same time, there were horrors swimming around that we are all too familiar with, including sharks. They may not have been the true kings of the time, but they were still highly successful,

playing the role of both scavengers and active predators, while also being one of the most commonly found carnivores around. Like many, these Cretaceous sharks apparently had a touch of gigantism, as a few types found in the seaway were among the largest known sharks. Although, in contrast to say dino-sucas, size didn't necessarily mean the sharks made the waters deadlier, since the biggest of them all, the tight codis, was actually relatively harmless to most. This was a mackle shark the size of a whale shark, but unlike the whale shark didn't use filter feeding, but yet was still highly specialized in its own regard, sporting a durofagist diet, meaning it primarily ate anything with a shell or exoskeleton.

This odd diet was deduced by the shark's teeth, which weren't sharp or serrated, but were instead fairly flat plates that were designed to crush. These teeth were abundant, sometimes numbering over 500, and could be absolutely huge, with the biggest recorded being longer than a ruler. These robust teeth would have allowed the shark to easily crush a variety of slow, hard-moving prey, like crustaceans or turtles.

Not all sharks are this docile, though. as when you do go down in size, you run into a still fairly big, yet much more voracious, toothy fish, the Kratoxirina, more commonly known as the Ginsu shark. Like Ticotus, this was a mackerel shark. But this one bore a striking resemblance to our very own Great White, while also sharing an oddly similar lifestyle, even though the two were not closely related, demonstrating a case of convergent devolution millions of years in the making. This was obviously terrible news for any animal around,

since it meant that the Kirtoxirina would have taken a stab at any kind of prey if the size was right. But it gets even scarier, because this shark was particularly good at killing a certain kind of animal. Active predators. That's right, the bulk of the Kretoxirina's diet came from other megafaunal marine predators, such as sharks, mosasores, pleasiosaurs, and fish, all of which have been found in the stomach regions of certain specimens. Such a diet indicates a hyper-aggressive animal and brings up the question of how it achieved such a feet. Well, the secret lay in its size and locomotion, as despite sometimes being eight meters

or 26 feet long, and weighing over five tons, it was still ridiculously fast, evidenced by the pattern of its placoid scales, which reduced drag and were organized in a fashion only seen in the fastest living sharks. Additionally, Kratoxirina had the most extreme case of a type four tail fin seen in any mackerel shark. Big news, as this type of fin supports high speeds, and models estimate that this giant could have topped speeds of 70 kilometers or 43 miles per hour, where its powerful jaws would have then come into play, dealing catastrophic damage, as they were lined with rows of razor-sharp teeth, which were bigger than those even seen in great whites, and also had thicker coats of enamel in order to survive these massive collisions. Fossil remains support the notion

of high-speed attacks, too, as nearly all bones found with bite marks belonging to this shark are extremely deep and large. And some of these said fossils have actually come from dinosaurs, showcasing the not even the rulers of the Mesozoic were safe. Albeit the dinosaurs in question, which were a hadrosaur and ankylosaur, were likely scavenged after their corpse had been washed out to sea. Yet, the Kertoxy rhina is still more than enough shark to fill anyone's gallopobia. But the Finn nightmares didn't stop with it, as you can't forget the presence of a smaller shark that still managed to make the waters even more, quote unquote, interesting, the Squally

Korax, better known by its nickname, the crow shark. It too is a mackerel shark. However, it was quite a bit smaller, normally measuring between 1.8 meters or 5.9 feet and 4.8 meters or 16 feet in length, similar to the size of a tiger shark. And its likeness to the tiger of the ocean went beyond its size, as its teeth were remarkably similar to, being numerous, relatively small, curved, and serrated, perfect for cutting and sawing through tough tissue. With such deadly teeth, the crow shark was capable of devouring many kinds of food that largely overlapped with the diet of the crotoxy rhina, with the major difference being that it went for the smaller individuals. Another difference between the two was that the crow shark tended to stick to more coastal areas and supplemented a larger portion of its calorie intake with scavenging, which again partially consisted of dinosaurs. It also developed a unique skill, hunting the rulers of the sky. In other words, the pterosaurs. Since, as opposed to other sharks, the crow shark has been known on more than one occasion to have successfully attacked large pterosaurs.

namely the Tyrannidon, which suggests that it had excellent vision that a use attract dinosaurs when they were getting ready to dive for a fish. And speaking of fish, crow sharks were pretty good at hunting them too, with many specimens containing large amounts of fish within their stomachs. Among the fish that have been found, there is one that has really stuck out to paleontologists, since it too is well known for being a famous sea monster of the Western Interior Seaway, the Zepactinus. You may recognize this name from certain documentaries, or you might be more familiar with its colloquial name, the X-Fish. It was a large bony fish that belonged to the now-extinct order, known as the Ictheodectiforms,

who were specifically comprised of ray-finned fish and were some of the meanest, ugliest fish to ever arise, with the X-fish being no exception, and probably holding the title as the meanest looking of the bunch. The main feature behind its terrifying looks was clearly its mug, which was broad, pushed back, and slanted. And while this face X'd any chance for a career in modeling, it's what gave the X-fish its fearsome reputation and status as a top predator, as the jaw was highly flexible, allowing it to virtually swallow anything small enough, which meant a lot, considering that adults could grow to be 5 to 6 meters, or 16 to 20 feet in length. At the lower size estimate, X-fish were capable of swallowing human-sized prey with one gulp, as depicted by the fish within a fish specimen, which showed a 1.9 meter or 6.2 foot length. long fish that had been swallowed whole by a medium-sized X-fish.

Furthermore, there are over a dozen other specimens that show similar findings. And on top of this crazy ability, this fish could still also cut through things with ease, thanks to their narrowed and sharp teeth, allowing them to both scavenge large animals or cut-up living ones that could then be swallowed in smaller pieces. This was definitely the last non-sharked fish you'd want to meet. And with the X-fish, you'd also start to arrive at the end of the list of sea monsters that truly made this place Hell's Aquarium. Naturally, though, there were plenty of other piscivores and carnivores that I didn't mention,

yet most didn't really make the seaway stand out in terms of deadliness. However, you really can't forget that there was one more iconic group present, the Pleasiosaurus. These guys, like the Mosasaur's, had four flippers, but the similarities stopped here, as pleasosaurs had broad flat bodies and short weak tails, while their necks could also be comically long, giving certain members the longest-neutral neck to body ratio of any reptile. To swim, they would have flapped their flippers in a flying motion and mostly stuck to the shallower waters. So far, multiple kinds are known to have inhabited the western interior seaway, with a bulk being plesiosaurids, while a few species of polycodolids

were present too. Some of them could get quite long and were typically over 15 feet or 5 meters from head to tail, with the longest having been the Elasmasaurus and Alberto Nectes, both of whom grew to around 11.6 meters or 38 feet. Such length gave them the longest necks of all time, and the elasmosaurus actually had the most vertebrae of any known animal, quite the accomplishment. But despite their daunting lengths and appearances, these long-necked reptiles didn't really have voracious diets, as they were simply highly specialized for small prey, given the narrow nature of their mouths and necks. It is believed that they would have used their necks to actually trick small animals like fish by approaching them with their mouths while their large bodies were

hidden out of sight, and thus giving them the chance to ambush prey. Perhaps even confusing a fish into thinking that they were a fish too. Once they struck, though, it was clear that they were no friendly fish. It's like many specialized fishers, the pleasiosaurids had teeth that were angled in such a way that they created a natural fish trap once closed. In addition to fish, it is believed that they also hunted snails, clams, and other small creatures. So, while not a person, predators, these guys were no doubt still highly skilled and successful, as demonstrated by their extreme level of diversity, which brings up the question of where did they and the rest of the crazy animals that called these waters home go? Well, some seem to have had a slow decline,

or in other cases evolved into something else. Animals also had to deal with the fact that the seaway was constantly shrinking. Although, what really changed the seaway for good was the asteroid that slammed into Earth 66 million years ago, causing extreme disruption and damage to to say the least. The impact was especially bad here compared to other bodies of waters, considering that the giant rock touched down rather close, sending a giant tsunami as well as other unpleasant trees through the waters, as evidenced by fish found with eridium in their gills. This devastation wiped out many of the more iconic sea monsters and finally brought an end

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