ExtinctZoo - The Scariest Animal During The Jurassic Wasn't A Carnivore...

Episode Date: October 6, 2024

The Late Jurassic Morrison Formation was one of the most brutal places to ever exist. You had giant sauropods and cannibalistic theropods roaming about, and still somehow, things got even crazier when you looked at some of the 'smaller' dinosaurs, with one herbivore in particular actually being more grisly then some of the predators around...

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Co-Pilot handles the spreadsheets. Learn more at M365Copilot.com slash work. 155 million years ago was just about the worst time you could be on land. This point in Earth's history marked the late Jurassic, and it was a period characterized by a pretty universal trend, giant saropods and theropods. Specifically, numerous ecosystems spread across the planet all seem to have had an abundance of predatory theropods and massive saropods running about.

And of every environment that followed this rule, perhaps the most extreme example was the Morris information, which was essentially the closest thing we've had to a real-life Jurassic Park. On top of grueling climatic conditions, which involved super droughts, it is here where you could stumble upon dozens of theropods that ranged in size from small to large, while also seeing over 30 kinds of sauropods, the vast majority of who weighed far more than an African bush elephant,

the current largest terrestrial animal. So it was without a doubt a land ruled by giants, which makes it all more impressive that one of the most successful and toughest animals was not a Titanic sauropod or theropod, but rather a medium-sized herbivore, that is also the only dinosaur evidence of having killed a fully grown allosaurus. This is Stegosaurus. Now, unless you lived under a whole mountain your entire life, you've likely heard of the Stegosaurus,

as it is among the top ten most well-known dinosaurs, and rightfully so, having one of the most unique appearances out there, which was even picked up on by its discoverers 150 years ago when they found fossilized plates, vertebrae, and other post-cranial material within Colorado. However, while they knew something was up, they were totally on the wrong path, as originally its founder, Othneil Marsh, suspected that Stegosaurus had been a giant aquatic turtle-like creature, whose plates acted as a biological roof, being overlapped across its back. And this is actually the reason why it was named Stegosaurus, as Stegasaurus means roof lizard.

Thankfully, though, not long after the original discovery, more better preserved specimens were unearthed. Yet these additional finds still took place during a time when paleontology was not super developed and therefore led to more inaccurate interpretations, including one that proposed it was bipedal and had spikes growing out of its back instead of tail. Meanwhile, other dinosaur bones were also being found

around the holotype, like those belonging to allosaurus and diplodocus, which only added more confusion as they were thought to have been a part of the stegosaurus. Eventually, a major breakthrough occurred, when a nearly perfect skeleton was found. This helped to quell any major confusion on how the bones were arranged, leading to finally the first reconstructions that looked a lot like those of today. In over many decades, as we learned more about the Stegosaurus,

reconstructions would be further fine-tuned, with the current consensus being that it was a quadrupedal herbivore that had vertically pointed plates on its back and four spikes on his tail, making it without a doubt a member of the Stegasoria, who were most closely related to Ankylosaurus. Within this clade, the Stegosaurus belonged to the Stegasaurida family, where it was joined by around 10 different genera, all distinguished by being more closely related to it than they were to the Chinese Huyangosaurus. Ten members made this family fairly sizable, and it was further bulked up by the numerous species that included three different stegosaurus species. As unbeknownst the most, this icon was not one dinosaur, but rather three different ones, those being Stegosaurus Stenops, umgulatus, and, and eulatus, andes.

and sulcatus. Each of them was very similar in a general sense, but they did have their differences, with the stenops having been distinguished by shorter legs and wider plates, while ungulatus was bigger, had longer limbs, and more pointed plates. Finally, you had the sulcatus, which donned highly unique tail spikes that were abnormally large and possessed big bases,

giving it a distinct appearance that has led to a few even pushing for it to be considered its own genus. But for now, it remains a stegosaurus species. Despite these differences, there is one thing they all had in common, and that was size. Because while Stegosaurus was not large for a morrison herbivore, it was giant for a dinosaur in general, with estimates suggesting an adult size between 6.5 and 7.5 meters, or 21 and 25 feet, resulting in it being considered the largest stegosaur we know of. Naturally, these numbers implied it was also quite heavy, possibly tipping the scales at 5.3 tons, which would have made it the second largest animal on land today.

What's interesting though is that we know for a certain that exceptional individuals got even bigger than this, thanks to a well-preserved specimen named Apex. Best known for being the most expensive dinosaur of all time, having sold for $44 million in an auction, Apex is also the biggest known Stegosaurus, measuring about 27 feet or 8 meters. And based on fragmentary remains, paleontologists further think that once in a blue moon, a Stegosaurus could have reached 30 feet or 9 meters in length. This size alone most likely made fully grown adults untouchable to a few Amorison's predators, like the Fosterovenator and virtually every Cillurosaur.

However, due to the sheer abundance of carnivores and the fact that a couple might have hunted in packs, there are still a good handful of would-be predators, including the Allosaurus, Sarofaganax, and Torvosaurus. And that it is for this reason that Stegosaurus evolved one of the most brutal weapons ever seen in an animal. It's Thagmizer. Don't be fooled by its funny-sounding nature, as the thagamizer refers to the four giant spikes found on the end of Stegosaurus's tail. Each one had an exceptionally sharp point and could grow

to be three feet or nearly one meter in length, making them longer than the entire blade of a katana. In most species, these spikes would have been arranged vertically, as opposed to horizontally, making upper, vulnerable parts of theropods viable targets. Once upon a time, though, there were some who actually thought that Stegasaurus did not use its thagamizer for defense, but rather for social display, with the main belief being that the tail was simply too rigid to allow for any meaningful swinging motion. Yet, subsequent studies showed that the tails lacked ossified tendons, suggesting that it was in fact very flexible in life, covering a swinging motion of about 180 degrees. Models and tests also found that it could be swung with deadly speed,

possibly up to 90 miles or 144 kilometers per hour. At this rate, each spike would have struck its target with the force of 1,000 to standard atmospheres, easily enough power to punch clean holes straight through thick bones, while also causing catastrophic damage to internal organs and structures. Things got more sinister, though, because since the spikes were narrow and long, they also created deep puncture wounds that were susceptible to nasty infections. So that's to say that even if a theropod did survive an encounter

with a stegasaurus of staghomizer, they could still very well die. And this is actually showcased by a rare fossil that represents just about the most unfortunate dinosaur ever discovered. To be exact, a 147 million-year-old allosaurus was found in Wyoming that had a peculiar injury to its crotch or pelvis. Talk about unfortunate placement. The wound was distinguished by being very deep and circular in shape,

bearing straight through the bone. And based on these characteristics, paleontologists concluded that the allosaurus had sustained this injury after a failed hunting attempt on a stegosaurus. is no other dinosaur animal possessed a weapon that could have made such an injury, and not to mention that a stegosaurus spike fits perfectly into the wound. Researchers further deduced that the unlucky allosaurus originally survived this encounter, but soon developed an abscess that likely caused it to limp severely for a few weeks

until it finally succumb to its injury. And sadly for all other theropods, such fates may have been quite common, as analysis on recovered stegosaurus specimens found that nearly 10% had injuries to their spikes, were consistent with high-speed collisions. In some cases, evidence even suggested that these giant spikes would occasionally get lodged in predators, similar to how porcupine quills do in modern times. For what it's worth, I should also mention

that there are other theropod remains, besides the one pelvis, that reflect a stegosaurus attack, including yet another allosaurus specimen whose vertebrae was absolutely skewered by a thagamizer. In this case, it's unknown if the victim died or was just named for life, as the wound never fully healed. Needless to say, Stegosaurus was one terrific dinosaur, whose design allowed it to hold its own

and turn the tables on large predators. And the Thagamizer was not even the full picture, as it had another adaptation designed to stop would-be attackers. It's Gular Armor. Even if you know and love the Stegosaurus, there's a chance you've never heard of Guler armor, as the vast majority of Stegosaurus finds lack it. But a few well-preserved specimens show that in life it had a strip of armor situated under the neck that was composed of pebble-like.

bony material. These bony pebbles numbered in the hundreds or thousands, and as a unit provided a good degree of protection to its vital arteries. Furthermore, while fragile and thin, Stegosaurus had plates on the top of its neck that along with its gular armor might have made biting the neck a very awkward task for certain theropods, and thus forcing them to try to find other areas, which likely brought them within striking range of its tail. And speaking of neck plates, we can't talk about the icon without discussing its back plates, as they were a huge, huge part of Stegosaurus's life. Ironically, in the beginning, many thought that it was these structures that deterred predators. Yet in reality, they were far too delicate to provided any substantial

defense, being made of very thin osteoderms that weren't even a part of the skeleton, and instead growing out of the skin in a vertical fashion, sometimes reaching 0.6 meters or 2 feet tall, while being just as wide. Although, their true size is unknown, as it is believed that while alive, stegosaurus had keratinous sheets that covered them, just like how many animals today have sheets that enlarge their horns. Estimates suggest that these plates would have numbered between 17 and 22 in total, and likely were used for social displays, while also helping to regulate the dinosaur's body temperature, as the outer layer had extreme vascularization, in other words, large amounts of blood vessels, and thus as the blood traveled through the plates, they would have

been cooled by the air passing around on the outside, a useful tool to have when you live in the morse information, where it could be both hot and exceptionally dry. And in true Swiss army knife fashion, there are other proposed uses for these plates too, including threatening display, a certain paleontologists think that the blood vessels could have pumped up the plates of blood, and thus giving them a deep bright red color, which could have made a predator think twice before trying to take a bite out of a thagamizer-wielding tank. Now, with all of this said, the stegosaurus was certainly bronze over brains, because while it had the power, the brains did seem to be missing. And I mean this in a literal sense. A stegosaurus only had a brain about

the size of a walnut, which relative to its huge body gives it one of the smallest brain-to-body ratio of any dinosaur, with its thinker having been roughly 57,000 times smaller than the rest of the body. And yes, while brain-to-body ratio is not perfect for gauging intelligence, many paleontologists have still interpreted the stegosaurus's extremely small brain as a sign of limited intelligence. And this belief may have actually had a role in the creation of one of the more common Stegosaurus misconceptions, and that is that I had a second brain. After Stegosaurus was first described, Marsh discovered what he called a large canal in the hip region of the skeleton. They could have fit an organ at 20 times the size of the brain. To him, this organ was another brain that he theorized

was used to control the back part of the body, and could be used to supercharged the Stegasaurus's decision-making skills during attacks. Although we now know course that this is not correct and instead it turns out that this canal house the structure not unique to stegosaurus a glycogen body the exact function of this organ is unknown but scientists reckon that has something to do with regulating glycogen throughout its body surprise surprise and now to be fair to the stegosaurus while relying on a walnut-sized brain does hint that stegosaurus was not the sharpest tool in the shed it should still be understood that you don't

need much brain to carry out simple functions like eating and knowing when to smash an attacker with your thagosaurus And if brains it did fail, then it could still rely on one more advantage. Numbers. Like many Jurassic herbivorous dinosaurs, stegasors lived in hurts, at least sometimes, as discovered trackways in Colorado showed a group of four to five individuals traveling in the same direction, while another trackway showed a baby and presumably their parent walking together.

This would have helped to dramatically increase protection, especially for the young, and it was essential in the morse information given the number of carnivores. Yet for large adults, it was a different form. story, as they likely needed little protection, spending a good chunk of their lives as solitary creatures, and demonstrating just how effective the stegosaurus was at keeping predators at bay. On top of this, while not specifically a carnivore deterrent, the stegosaurus had some pretty messed up teeth, too, that were unlike anything seen in other ornithicians, as its teeth, numbering around 78, had strange indentations on the top that gave them the appearance of being

a bit sharp. Not to worry, though, because stegosaurus was still undoubtedly a herbivore. It's just that we aren't really sure how these odd teeth functioned, with the best guess being that they were designed to snip plants in half and partially grind material with each bite, which based upon its skull operated in an up-and-down fashion. Given its habitat, paleontologists think that the plants included in its diet consisted of mosses, ferns, horse tails, cycads, and conifers, which were abundant during the late Jurassic. It was perhaps thanks to these plants that Stegasaurus achieved a considerable range, showing up in five different states in North America.

And not to mention that it went a bit international too, as remains belonging to the ungulata species, were discovered in Portugal's Lorinia formation. At first glance, it might seem weird that Stegosaurus was both in North America and Europe. But it actually makes quite a bit of sense, when you consider that at the time, the two continents were much closer than they are today. And the Stegasoria group might have actually first started out in Europe,

before migrating over to North America at some point. Naturally, though, living in two distinct areas brought the Stegosaurus into contact with a whole host of dinosaurs that included a gopsmacking amount of saropods and theropods, such as the allosaurus, serratosaurus, Sarophagenax, Torvosaurus, Fosterovinator, Ornithelestis, Lusovinator, haplocanthosaurus, marapunosaurus, suasia, apatosaurus, brontosaurus, brachiosaurus, Diplodocus, Ampheselius, Lusotitan, Oceanotitan, Barrosaurus, and Suprosaurus. And this is really only scratching the surface, because not to mention that other dinosaurs are present too, like various anchylosaurs, iguanodontids, and dryasorts.

And while dinosaurs alone made the stegosaurus environments, especially the Morrison, quite hectic and full, they were, of course, not the only ones around, as non-dinosaurus consisted of fish, amphibians, crurotarsons, chrystoderees, turtles, squamates, sphenodonts, invertebrates, mammalia forms, and pterosaurs. With so much life, you must be thinking that Morrison surely was a safe haven for animals, minus them eating each other and all that. And yet, while it could be very resource abundant, the Morrison formation was also at times the closest thing to hell on Earth, as it essentially experienced super drought. Studies indicate that this environment had two distinct seasons, wet and dry, where in the latter, resources would rapidly dwindle and bodies of water would shrivel up, putting catastrophic pressure on the ecosystem that induced widespread thirst and starvation, leading to an extremely high rate

of cannibalization amongst theropods. Strangely, though, or not, considering how metal it was, the Stegosaurus seemed to have thrived on this chaos, at least more so than others, as the location of Stegosaurus remains usually aligned with the drier parts of the Morrison, showcasing a preference for the more arid areas, in which other dinosaurs tended to be fewer and far between. Its ability to weather the storm, or lack of, is also reflected by its extended existence of over 10 million years, above average for a Morrison animal, and one more reason why the stegosaurus is such an icon. But for all of its amazing traits, the stegosaurus never saw the end of the Jurassic period, dying out just as the last stage.

began. It's not 100% established what took out this absolute unit, but paleontologists speculate that flora and fauna turnover created great changes in the environment that slowly chipped away at the Stegosaurus, with the shifting climate, adding fuel to the fire with its own obstacles, and ultimately overpowering just about the toughest dinosaur to have lived during the late Jurassic. But like I mentioned, the Stegosaurus was not the only animal to have lived during this hellish period. And in fact, I made a whole video talking about this time frame in general, which goes into a lot more depth on why this period was possibly one of the worst times to have ever lived. So if that sounds interesting, check out the video on the recommendation.

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