ExtinctZoo - T. Rex Had A Rival And Nobody Talks About It

Episode Date: January 13, 2026

Move over T. rex, mister drippy is coming through

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Monopoly is a trademark of Hasbro. Hasbro is not a sponsor of this promotion. 66 million years ago, across the plains and forests of Cretaceous North America, the most iconic dinosaur and possibly the largest terrestrial predator of all time was stomping about. The ever infamous Tyrannosaurus Rex.

It's hulking size, Titanic Jaws, Banana-Sides, killer teeth and lovable tiny arms and made it a fan favorite and an unforgettable creature. And honestly, you'd be hard pressed to find a paleo documentary or movie without it, especially if it's one about the end of the dinosaurs' reign. If they show you a comet, you can bet that somewhere along the way, you're going to see a T-Rex. But here's the thing. You may not know that the T-Rex belonged to the super family known as the Tyrannosaurus,

of which many members have existed and ruled North America's the top predators all before the T-Rex even came about. We had the Gorgosaurus, Appalachosaurus, Daspletosaurus, etc., etc. However, even then, we usually think of the wrecks of the greatest of its kind to live, and also the very last one to be left standing. And yet, it turns out that another one of its kind, not only basically lived right alongside it, but was also present on that fateful day when the asteroid came hurtling down,

and you've likely never even heard of this dinosaur, nor seen it in any dinosaur documentary. As thanks to its more quote-unquote interesting brethren, it has largely lived under the radar, despite being not only an absolute menace in its own right, but also the co-ruler of North America. This was the Driposaurus. Like I said, you probably never heard of this guy before, and it's not because the theropod was just recently discovered. No way, Jose, as it was actually one of the first theropods to ever be discovered, and the first

large one from eastern U.S., being unearthed all the way back in the 1860s, before sliced bread had even been invented. Prior to its discovery, theropods from America, had only been known through a few fragmentary teeth. So you can bet people were surprised when a mineral company uncovered not just teeth, but a body of a theropod skeleton in a quarry near the state of New Jersey, that contained fragments of the skull, dentory, various teeth, vertebrae, hume, a partial manis, incomplete pelvis, and a nearly complete left-hind limb.

To paleontologists, it was clearly a bipedal carnivorous theropod. Yet, given how far back it was found, they did struggle with classifying this new creature. At first, numerous scientists noted clear similarities between it and the Jurassic dated megalosaurus, and thus leading to it being classified as a megalosauroid. It was dubbed originally as laylapse aquilunguous, after the dog in Greek mythology that never failed to catch its hunt. However, turns out that a mite was already called laylapse, and thus it became driptosaurus, meaning the one with all the drip. Just kidding.

It actually means tearing reptile, and soon this tearing reptile found itself reclassified once more, being dubbed some kind of Solarosaurus with an uncertain placement, as it had some unusual features that didn't fit in with anything discovered thus far. It was only in the mid-1900s that people finally started to note some similarities between it and Cretaceous tyranosaurus, namely the Albertosaurus and Tyrannosaurus, with the three sharing certain arm morphologies and derived feet. And these loose connections were finally confirmed in 2005, after the most complete specimen to date was unearthed.

Demonstrating the Driposaurus, given its appearance and features, had indeed been a member of the Tyrannosauria, and specifically was the U-Tyrrinosaurian. However, it turns out that it is likely not a member of the more specific subfamily, Tyrannosauridae, with its closest relatives instead being the Appalachosaurus and the Bistaheverser. That being said, though, it is essentially the closest relative to Tyrannosaurids without actually being a true one. And so this was a cool revelation, no doubt, but what had everyone a bit more interested was not its placement but the timing of the Dripdosaurus. As, lo and behold, not only did it live in the United States, but it dated to between 67 and 66 million years ago,

putting it side by side with the T-Rex. And yet, the Driptosaurus is often forgotten about, and it's certainly not a case of it being small enough to have gone right under our noses, as Driposaurus was a rather large North American theropod within its own right. Based off the specimens, it's believed that matured individuals would have reached up to 7.5 meters or 25 feet long from snout to tail, while weighing somewhere around 1.5 tons, putting it on par with the largest seen serratosaurus or a mid-sized carnatoris. So yes, no T-Rex, but was still more than big enough to kill you, and a very wide range of Mesozoic animals. And given its size, you might have actually mistaken one of these coming after you for an actual Tyrannosaurus adolescent. But there were some clear

distinctions between it and the T-Rex. For starters, the driptosaurus possessed too small, yet distinguishable crest on the top of its face that were located right below the eyes, perhaps being used for mating display, while its snout and body were in general more streamlined and agilely built than the skeleton of a Tyrannosaurus. It could have also been further distinguished, thanks for reduced humorous, an expansion of its ischial tubercle, in ovoid fossa, and a flat shaft on its fourth metatarsal. Yet, to be honest, if one of these is coming straight at you, I highly doubt you'd have time to care about any of these more specific, nuanced differences. Now, what you would definitely care about, though, was another feature that set it apart from the T-Rex,

and actually, for the worse, and that was its arms and claws. I know you all are aware of the T-Rex's arms. They are small and kind of adorable. However, the Driposaurus's arms were anything but that, taking more inspiration from its ancestors. As in this theropod, the arms remained long, large, muscular, and equipped with ferocious claws. In its case, ones that can measure up to 8 inches or 20 centimeters, which, just for perspective, is over three times the length of your standard common Swiss army knife's blade.

And for the one with all the drip, these arms would have definitely been used for combat and hunting, helping individuals to capture prey and tear straight through them. While then, it also, of course, had some wicked teeth to go along with the package, with each being serrated and curved, perfect for slicing and dicing flesh like it was hot butter. And actually, the teeth are remarkably similar to those seen in the Jurassic allosaurus, and thus implying that the prey of Driposaurus was always in for a bad time, with each get-together, so to speak, involving major blood loss and shock. So physically it was quite the package, and it possessed the typical other strengths seen in its kind,

namely a keen sense of smell, allowing it to pick up on prey and carry-on, as well as binocular vision, which helped it to lock onto targets with deadly accuracy. So all in all, it was definitely an expert killer. The question is, though, what exactly did it kill? And this question indirectly leads to an interesting tidbit about the Driposaurus and the T-Rex, which is that while the two lived at the exact same time, and in the exact same country, as far as modern borders go, the two didn't actually ever come face-to-face, as far as we know. And the reason for this is that the Driposaurus inhabited the continent.

of Appalachia. You see, at some point in history, North America was divided, and I don't mean like now or during a civil war, but rather by a geological feature, the western interior sea, which was a shallow, warm sea that split the continent into two, and created the paleo-continent of Laramidia to the west, and Appalachia to the east. Typically, dinosaurs found in one of these places weren't really found in the other, being restricted by not only the waters themselves, but the nightmares they harbored, and leading to both sides, developing very unique ecosystems. In Appalachia was by far the more enigmatic of the two, as its formations have yielded far less fossils than Laramidea has. Now, what we don't know for sure, given how hard it is to analyze the prehistoric past,

it's often believed that by the time the final chapter of the Cretaceous began, the Western Interior Seaway had shrunk considerably, possibly even resulting in a reunification of certain parts of the continent. Yet, Appalachian Laimedia still remained fairly isolated from one another, perhaps due to periodic flooding from sea level fluctuations, but also because even when two areas, is connected once again, it can take a while for migrations to start up, and it seems that Driposaurus was never given enough time to make it to Laramidia, nor vice versa for the T-Rex, that's allowing it to be the sole ruler of late Cretaceous Appalachia. And this ultimately meant

that the Driposaurus was ruling over and hunting different dinosaurs than the T-Rex was. So, let's just say, you wouldn't have seen this there about taking on a triceratops, for example. Though that being said, based on the formations it has been found in, it did likely prey on various hadrosaurus, like the hadrosaurus, or have to have. cadresoroids, such as the basal, yet giant, hypsibema, that might have weighed over 10 tons and measured over 12 meters or 40 feet. Multiple notosaurs were also known to inhabit the continent, which could have proved a suitable meal, yet hunting these guys, given their better armor, would have been kind of tricky for the driptosaurus, especially since the lack of the crushing bite seen in its larger relatives.

And then seratops and saropods were pretty much out of the question too, as they were straight up missing from the continent, having been absent in the lands at the time. Except that is for a single seratops tooth, which was found. on what is currently Mississippi, that possibly showed migration towards the very end. However, a driptosaurus has also never been found in a formation with the serotops tooth, and clearly it seems that whatever the case, serotopsines in Appalachia were exceedingly rare. However, what was a bit more common and could have made up an ample portion of the driposaurus' diet were actually fellow theropods, namely ornithomimosaurs, who appear to be quite abundant in the east.

And this notion is actually rather in line with the build of driposaurus, with its streamlined body and grasping arms, which probably allowed it to hunt and capture these fleeting prey, that could also, by the way, get quite sizey here as well, since Appalachia at the time was home to numerous large-bodied ornithomimosaurs, including some of the largest to ever exist, namely, an indeterminate kind that weighed close to one ton. So, picture about three ostriches rolled into one giant. And to go along with a little dinosaur here and there,

the drubterosaurus might have been something of a generalist too, as up until now, the vast majority, and possibly all the areas that it has been found in, would have been coastal and near marine environments during the late Cretaceous, environments that were chalked-fold in both aquatic and semi-equatic life. In the waters full-time, this included a variety of cartilaginous and bony fish that included larger ones, such as the shark-sized cepactinus, as well as marine reptiles like multiple medium-sized mosasors and pleasosaurs. Then around the water's edge, you would have found a plethora of amphibians,

including frogs, toads, and even salamanders. But certainly not salamanders like you may think, as these guys were chunky ones. definitely being able to make up a good snack since they were over 5 feet or 1.5 meters long. And on the even bigger stage, there were also many different turtles like Korsiakalus and aidochus, plus lizards and even various mammals, such as the diphylodon, a metatherian that was only slightly larger than Virginia opossum. And yet, that was still good enough to make it Appalachia's largest mammal, and actually one of the largest mammals on Earth at the time. But this is all to say that the Drptosaurus at various stages of its life and a few options to choose from when it came to snacks. but it would have needed to tread carefully.

Now, the driptosaurus is for now the largest known theropod from Appalachia in the final days of Cretaceous, plus the overall largest carnivore from the region as well. But there was still some competition, mainly in the form of crocodilians, as there were lots and lots of them. Multiple genera were known to share Appalachia with the Tyrannosauroid. It could range from smaller sizes, like the size of your leg, all the way up to crocs that you might have confused for an alligator. And while nothing, alligator's size is going to scare a fully grown driptosaurus, I doubt the juveniles would want to encounter these crocodilians during one of their adventures. Nor, in fact, would they probably want to meet another apex predator of Appalachia, a terasaur.

Now I know what you're thinking. We don't usually think of terrorsors as being all that scary. Yet in Appalachia, they sure could be. You first had your standard residence, like the Tyrannidontoid's and related kin, which might have actually made for an occasional meal for the Driposaurus. But then you also had the Azdarkaday, a group of pterosaurs that could be quite a doozy. And in Appalachia, the mightest of the lot was no doubt, the Aramborgyania, one of the largest animals to ever fly. In fact, there are only two other animals that rival it or exceed its size, the Quetzalcoatlas and Hatzigopteryx, two close kinds of it. And let's just say, this behemoth was basically a living dragon, minus the flames, and it could have had a wingspan of up to 10 meters or 33 feet, which is like the wingspan of a

Cessna 150, a literal plane. But what was arguably even more bonkers was that its neck alone was 3 meters or 10 feet long, taller than Shaq. And overall, on the ground, the Aramborgiania might have stood as tall as a giraffe, and thus making baby driposaurus is quite the edible option. But I will say that a fully grown driposaurus, on the other hand, likely could have been able to take down even the fully grown individuals. So overall, I'm still giving this round to the theropod. Now, I should mention, though, it is important to note that the remains of Aramborgiania found

in the U.S. are tentively assigned to this genus, and are a little bit older in age than the Driposaurus. However, where it is found elsewhere, the ages of Aramborgiania do extend to 66 million years as well, meaning there is a good chance that the two did coexist. And honestly, even if they lived together or didn't, the Driposaurus still had a pretty sweet gig in Cretaceous Appalachia, enjoying the benefits that came with isolation. And it would have been really interesting to see how this Tyrannosaurid would continue to evolve and change if it had remained untouched in Appalachia, or had moved on over to Laramidia, perhaps coming into contact with his long-lost cousin, the Rex. Yet, unfortunately for our thought to experiment, Mother Nature or the cosmic universe had other plans.

And the Driposaurus only first appeared 67 million years ago, so a baby for a dinosaur. And sadly, it did not stick around for long, as just one million years later, the Dino's party came crashing down. And similar to the Rex, the Drptosaurus was wiped away in the KT extinction, officially ending the rather short reign of this co-ruler of North America that has largely been forgotten about. Thanks for watching, and until next time, on Extincts through. You're great at protecting your data, but lots of places could still expose you to identity theft. I thought it was safe. If that happens, LifeLock gives you a U.S.-based restoration agent who will stick by your side from start to finish. Phone calls, filing documentation, preparing insurance

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