ExtinctZoo - The World Right After The Dinosaurs Died

Episode Date: August 16, 2025

Dinosaurs may have fallen 66 million years ago, marking the end of an era and ushering in an age which would eventually come to be known as the age of mammals. But the journey to get there wasn't as simple as some might believe...

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different shapes and sizes. And for a while, it seemed like Earth would be forever theirs. However, this possible reality was squashed 66 million years ago, when their party suddenly came to a violent halt. You know the story. A giant asteroid the size of a mountain slammed into the planet with enough destructive force that within a day, Earth had been entirely transformed into an apocalyptic wasteland, making the dinosaurs no more. Or at least, that's what you've been led to think. Because while non-avian dinosaurs are definitely gone, research are, do universally agree that at least some survived the initial D-Day and possibly held on for a surprising amount of time, perhaps hundreds to even thousands of years. And obviously, this is quite

a range, and it isn't exactly set in stone either, no pun intended. Therefore, it's impossible to say exactly when the Earth saw its first day without the dinosaurs. However, at the same time, we do have a general idea of what that day might have looked like, seeing that we have a whole stage that began right after the Cretaceous ended, and it's a time that surprisingly, has gone largely forgotten about. This was the Danian, the Earth after the dinosaurs. So what was it like? Well, it's surprisingly actually pretty straightforward if we do pretend that all dinosaurs

disappeared immediately. The asteroid's collision had caused immense physical devastation on a global scale, and much of the world would have looked like a complete war zone, with virtually no trees, plants, forests, or animals being found anywhere. After all, about 75% of all species have been eradicated. while those who had survived were in very poor straits and hunkering down. Beyond just the absence of life, you'd also notice that the world was freezing and nearly dark, as the asteroid had sent enough material flying up into the atmosphere,

that large amounts of sunlight was now unable to reach the surface. And for three years, you could expect perpetual darkness akin to a moonlit sky. During this time, you'd also see fungi slowly overtaking the lance, as fungus usually thrives in the wake of mass death, and have the added benefit of not requiring sunlight, with the fossil record reflecting this through a thin line wherein fungus was extremely common. However, this apocalyptic earth likely isn't the best representation in the world immediately after the dinosaurs, since as I mentioned, they probably lingered on for a bit. And these nightmarish conditions

also did not last that long, with the world recovering surprisingly fast, with life even returning to the crater site within just a few years. Therefore, in order to see what Earth was truly like following the dinosaur's reign, it's best to skip through this brief yet no doubt tallish phase, and instead revisited the world once things settled down and was once again a bit lively, albeit a bit less dinosaury. At this point, the Danians still wouldn't have looked too different from the final days of the Cretaceous, at least from space, seeing that most of Earth's landmasses were pretty much where they had been beforehand, and despite a few differences, any map would strongly resemble the world as we see it today. In addition to geography, the climate hadn't

changed much from the Cretaceous period either, with the temperature being warmer than present on average, while most areas were more humid as well, resulting in many environments supporting subtropical ecosystems. But beyond these similarities, the Earth could not have been farther from what it had been, and the first large change you'd probably observe was the landscape itself. To be exact, the trees that now stood. During the final days of the Cretaceous, conifers, ferns, monocots, redwoods, ginkoes, and angiosperms were among the most dominant tree types. In the last large, expansive forests with dense canopies covered much of the land, providing ample coverage to varying life and supplying an abundance of vegetation for the giant herbivorous dinosaurs.

Yet in this new day and age, forests were a bit less rich than before, and much less diverse, with many of the previously dominant groups having been almost completely wiped out, especially ferns and monocots. And there was pretty much only one group that even benefited from the asteroid, and that was conifers, as the genus, Classopolis in particular, became strikingly abundant, while Bue, was fairly prevalent as well. And these couple of trees and plants are ultimately what made up much of the vegetation, leading to extremely homogeneous forests, no matter where you traveled.

Now this would change a bit as the Danian developed, with flowering plants slowly overtaking all else, a trend we see reflected today. But the lack of diversity would remain a theme in forests for a far longer time. And when exploring these new forests, you'd probably soon come to another observation beyond diversity, one that was much more ominous. that's how quiet it was. Not so long ago, these areas would have been full of the roars and bellows of giant dinosaurs, terrors and so on. Yet now, nothing, or at least almost nothing. For life was still present, just on a much smaller scale, literally, as the Danian stage was home to

animals much smaller than before. And even the mammals, who were now in charge, weren't even close to reaching modern sizes, meaning you could pretty much walk around without having to worry about getting snatched up, which is quite the shift from the Cretaceous. But, that being said, not all of the legacy of the Cretaceous have been erased just quite yet. As the Danian formation tells us that specific animals from the dinosaurs' age had survived into this new planet, representing the last pieces of a lost world. Some of these survivors even became among the largest creatures of the time, and were funnily enough, not usually mammals, but ironically, reptiles once again, namely it was the

crocodilomorphs who were living it up. having fared quite well during the collision, largely thanks to their physical design, as well as lower energy requirements and chosen environments, which typically were sheltered. And as a result, they could be found worldwide, and in many cases, were likely apex predators, being represented by the genera such as the Bodasaurus, Hyposaurus, Theracosaurus, chamsasaurus, and borealisus, the latter of which are two crocodilians who literally lived alongside the legends, having both been residents of Hell Creek. These crocodilians, together, would have held very diverse diets, and they were a bit sizey,

sometimes measuring over 3 meters or 10 feet long, which was rather big back then, and Borealisukas Succas could be even bigger, growing to lengths of 4.5 meters or 15 feet long. Now, most of these crocodilians ended up inhabiting shallow, semi-aquatic ecosystems, but a few others ended up choosing land instead, like their co-existing cousins, the Sebechidae, a fully terrestrial group that had also endured through the asteroid. and were now represented by the Zulmasukas, a Bolivian genus, who was a bit small, but still likely had a rather nasty bite.

And with the dinosaurs no longer bowling his kind, his descendants, especially the Burinusukas, would actually become just about the largest terrestrial carnivores since the T-Rex. Talk about a glow-up. And along with the crockies, another group of reptiles that found themselves doing well to the misfortune of some of us, today, were snakes,

and they survived for very similar reasons to their distant relatives. And honestly, they should have even thanked the asteroid, because while a few groups were wiped out, the lack of competitors going forth led to a massive burst in serpent diversity, and leading to a new status quo that has lasted, with the main change being that boas became quite common and were relatively big compared to other Danian life, and could even, like Crocs, sometimes measure over three meters or ten feet long. Another shift you would have noticed, which again occurred in the reptile department, was that both iguanas and monster lizards had become predominant animal.

animals in various ecosystems, with the latter even joining the ranks of top predators, likely rivaling the size seen today in modern ones. And the reptiles seemed to keep on winning, because there was actually one more group that had all three of the other groups beat when it came to thriving, and were even a short-time ruler of the earth after dinosaurs. And that was turtles. Now, they're not the most intimidating creatures out there, but turtles are hella tough, and I'm not just talking about their shells, with them having both an adaptable diet and a

slow metabolism. In fact, when it came to surviving the space rock, they did just about the best of any group period, better than even mammals, with researchers estimating that 80% of Cretaceous turtles made it into the Cenozoic. And just to put that into perspective, can you guess how many mammals made it? A measly 7%. Thus, for a long time, turtles were killing it, being abundant, diverse, and everywhere. The only drawback to this was because turtles are typically the gentle type, well, at least of some aspects, animals, their high prevalence also resulted in them becoming a huge prey source, with fossils showing that crocodilians especially love to prey on our shelled friends.

So, it seems like Earth immediately after dinosaurs was more reptilian than you would expect than the so-called beginning of the age of mammals. Yet don't get it twisted, because there was much more mammals than before, and they were far bigger, for the very first time, reaching sizes larger than a sheep. But for the most part, they remained fun-sized, and were even a bit adorable, with some new faces, including the polydopamorphia, an extinct order of metathurians closer related to extant marsupials, who had actually been one of the most successful group of mammals in their Cretaceous, with a particularly prominent family during this time being the highopsodontidae.

They fell under the pan-parasidactyl acclade, making them more related to zebras than to rodents, despite their appearance, and generally ranged in size from a small rat to a raccoon, and were likely generalistic eaters that would nip on just about anything that was small enough. But unfortunately, they two were now extinct. Besides them, marsupials were now in the prowl as well, in numbers far larger than before, with the microbiota theory of family, especially having been prevalent in the Danian. Yet, as cute as these guys were, they aren't exactly all that interesting, and frankly, none of them really were.

But I will say, mammals as a whole were testing the boundaries, expanding and experimenting. And in these early days, you could have actually caught a glimpse of possibly the first mammals to ever be apex predators, and who were also, the largest mammals up until this point, the Mesonikians. They were a primarily carnivorous or omnivorous group of animals that in whichever case ate a lot of meat reflected by isotopic analysis. They appeared on Earth almost right after the end of the Cretaceous, becoming the first fully terrestrial mammal group to really take advantage of the disappearance of large theropods. And while they are often reconstructed as having superficially looked a lot like wolves,

if you ever saw them in life, you'd probably make no connection between the two, as most paleontologists assert that they didn't resemble any living creature, generally being described as sporting large heads with powerful jaw muscles, having relatively long necks, and large robust bodies with stocky limbs. That did allow them to run, but not very gracefully. And if they were chasing you, you would have noticed that they bounded more like a rhino than a lion. And this kind of makes sense, seeing that they were actually more related to rhinos as well, being ungulates after all, not carnivorans.

And during their existence, Meso-Nikians greatly ranged in size. and one of the most successful the bunch would have been the disikis, a coyote-sized member who seemed to play the role of a fox or small canad, just on a bigger scale, being actually amongst the larger animals in its homeland, which consisted of North America, Europe, and Asia. And while it was a bit clunky in the running department, it did actually possess additional adaptations for locomotion, so much, in fact, that some paleontologists think it might have held a monopoly in running over all other animals, which was a bit unfair when you realized that it was also the largest animal, around in its ecosystems, which was only made worse by the fact that Mesonikea would soon get even bigger. Best demonstrated by the Anne Callaghan, another Damian creature that reached size is akin to what's seen in modern bears. However, in my humble opinion, they were a bit more scary than bears, and for a reason

what you think would make them safer, and that's blunt teeth. Now obviously blunt knives typically are safer than sharp ones, but An Calagon reversed this, is at the end of the day it still had to eat and ate meat, and thus it evolved an extremely only strong bite, basically erasing the need for sharp teeth as it would kill animals by biting so ridiculously hard and then as ripping the meat straight off of it. So, uh, not a good way to go. And ultimately, the mesonikids would develop many ways to kill in their early days of their dominance, with some showing teeth similar to what's seen in bone-crushing hyenas, while others had those more similar to what's seen in pigs. It was all about the variety. Now, these were the biggest mammalian

carnivores, but they were also joined by the smaller, but equally interesting, hyena danta, which are not to be confused with real hyenas. This was a family of hyper-carnivorous placental mammals belonged to the Ferrymeree mirror order, which basically means they're related to modern-day carnivorans and pangolans, as opposed to ungulates like the Meso-Nikians. And these guys might have actually appeared during the late Cretaceous, when the dinosaurs were still around,

but they only really started to diversify in the Danian. And similar to Mesonikids, they too had relatively large skulls, yet differed in that they sported slender jaws and slim bodies. And as mentioned, they were smaller too, with Danian hyenodonts typically being no larger than a medium-sized dog. However, while size was not on their side, they did have the advantage of superior smell, allowing them to become expert trackers. And their teeth were much sharper, designed for shearing over crushing. And ultimately, their design would come to haunt the mesoninids. For while they ruled the Danian, the hyenodonts would eventually take over, becoming the most important terrestrial predators during the Allegasine, and reaching sizes greater than a polar bear.

But for now, they stayed small. And if you were a carnivore, being small was apparently a strict memo back then. As other carnivorous groups you might have seen, included the Biverevide, Myasida, and Simolesta, who were also in some cases omnivores and herbivores too. So between these hunters and the smaller herbivores that stock the lands, you basically have your answer on what replaced the non-avian dinosaurs. But what about the pterosaurs? I mean, after all, they did dominate Earth for millions of years, too, holding absolute

domain over the skies. which begs the question, who replaced them? Well, in the beginning, not too much, with insects, frankly, being the ones in charge. But even they hadn't fully recovered at this point, which is great news for any of our time travelers who hate creepy crawlies. But even better news for them would be that out of the groups which remained, one of the most prevalent were butterflies,

a pleasant change for once. But of course, besides insects, you also had the remnants of dinosaurs flying around too. Birds. However, like insects, they were hurting. And contrary to popular opinion, only a small handful of them made it past the Cretaceous. And though today there are without a doubt the rulers of the sky, they had not to reach this point during the Danian, with their full recovery taking an additional 15 million years. But you know what doesn't take millions of years?

Taping that like and subscribe button. It goes a long way in helping out. But overall, in the end, the lands of Earth weren't the most exciting after the dinosaurs. But it was made up for a bit by what was unfolding underwater. Just like the land with its non-avian dinosaurs, the oceans and seas had lost their undisputed rulers as well, namely large marine reptiles, like mosasors and pleasosaurs. However, in their absence a new group arose, and once again, I may add, who also survived remarkably untouched and aren't exactly more comforting than having marine reptiles swimming about.

And of course, I'm talking about sharks, lots of them, in fact. Of the 28 shark families known during the final days in the Mesozoic, just three when extinct, leaving 25 groups still swimming in the Danian. And they weren't exactly small or timid either, as among the numerous genera you would find the largest predator alive on earth during this time, who was also a great reason to never swim. The Otitis, meaning ear-shaped tooth. This was a genus of mackerel shark, just like Great Whites, that is believed to descendant directly from the shark, cradle lamna.

And with the absence of giant mosasaurus, Odidus was able to quickly swell in size. and less than one million years after the Cretaceous, there was not one, but two species of odotus meandering around, that already matched the size of large great whites, allowing them to basically eat anything they desired, which was typically sea turtles and fish. And then, on top of these big guys, there is also the chance that a third species was on the scene too,

the obelicus, which if the case was a very, very bad omen. For this species was even bigger, sometimes hitting nine meters or 30 feet long. And while the odotis species were, unchallenged when it came to size, they definitely weren't the only sharks taking full advantage of this emptier world, being joined by some genera that have even made it to today, like the lamna and nebrious. And besides sharks, there was also many other groups that were popping off, including sea turtles, like I mentioned, eels, with them heavily diversifying at this time,

and then while not marine per se, it was also now that Earth saw the rise of the Anguilidae, a family of ray-finned fish, which contained freshwater eels, not to be confused with their marine counterparts. But for those Unagi lovers out there, best be thankful for that space rock. Along with this bunch, we also got the first cutless fishes back then, a group that like freshwater eels are still living and are predatory fish, yet are a bit of meaner looking, possessing relatively large fang-like teeth, which allow them to pierce and hold prey tightly. And in the end, they weren't the only strange fish to have popped up in their early son is Zoic. As one of the strangest, actually happened to appear right around the impact crater not long after its formation.

and calling it weird as putting it lightly. Perhaps it got mixed up with some of that good old meteorite dust. This was the Ecolostomis. It's a completely extinct genus who belonged to its very own family, of which it is the only known member. It can be simply summed up as an alien-like trumpet fish. As besides the trumpet part, it was also completely armored, kind of like a placoderm.

However, its armor was even weirder than what's typically seen in placoderms, being very rough, unsymmetrical, and protruding, making it kind of look like a cross between a coral and a theroderm. fish, or at least a fish with a serious barnacle overgrowth. And though we don't know much about this creature beyond a strange appearance, we do know it was important, in that its existence itself showed to us that marine life near the asteroid's crater recovered rapidly, and seemingly harbored predators, too, given the presence of its armor. And overall, strange definitely seemed to be the trend for Danian fish, as I present you yet another oddity, the Adaphaon.

Now this genus was actually a remnant of the age of dinosaurs, having evolved during the early Cretaceous. Yet even after the asteroid, it remained a fairly common sight. Everything we know about it points to it having been a type of chimera. And no, I'm not talking about the mythical creature, but rather the equally weird-looking fish that are cousins as sharks and rays that still do swim in the oceans today. But unlike its living relatives, this guy was an absolute unit, sometimes measuring more than 3.43 meters or 11.3 feet long, which also makes them larger than the biggest Goliath groupers out there. Now, the late Cretaceous had been their peak.

But even during the Danian, they were still widespread, living in both the northern and southern hemispheres. Word is thought that for a brief time they would have been among the Earth's top predators. But what they ate exactly is still a mystery. As unlike sharks, they did not have many sharp continuously replaced teeth, but rather large permanent tooth plates that at least in some species seem to be specialized for a mix of jobs, including crushing, cutting, and tearing, leading to the idea that large adaphidons probably ate whatever they wanted, including hard-shelled animals, fish, sharks, and any marine reptile

stragglers left behind. However, like Ecolostomis, they would not make it to the present, and would eventually be replaced by sharks and other predatory fish. But they did last for far longer, making it all the way to the pliocene, and they also would not be the last to disappear, as actually an animal typically associated with the age of dinosaurs is believed to have briefly survived following their demise. And that's the Ammonites, an extinct subclass of co-coiled-shelled cephalopods that existed for hundreds and millions of years, and would have been a common site in nearly all prehistoric oceans and seas. And for a long time, paleontologists believed that all of them, without exception, had perished on the fateful day. But then in Denmark and New Jersey

respectively, paleontologists found the remains of a species dated to after the impact, suggesting that a handful remained for nearly 500,000 years. And these genera included the Eubacalytes, Disco-Scafites, Hoplo-Scafites, and Baculites. And while none were as giant as the older parapasosia, they were still extremely interesting and unlike anything we have today. And along with the rest of the animals that had made it through the boundary were the last remainders of a world lost a time. Thanks for watching. And until next time, on its time, enjoy more ways to save at Ralph's like low prices in every aisle. And when you download the Ralph's app, you can clip and save more with digital coupons every week. Plus,

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