Transcription
When you close your eyes and picture Antarctica, what do you see? Probably lots and lots of ice, with maybe a few penguins sprinkled in. And if you go past that and try to imagine even more of it, then what do you get? Likely even more ice. After all, the continent alone accounts for 90% of the Earth's total glacier ice, and in some places, it is miles or kilometers thick.
To many, Antarctica has always been like this and will presumably always remain like this. However, that's not actually correct. As once upon a time, not only did Antarctica have less ice, but it was instead a world of lush greenery, highly bizarre animals, and owner to a rather tragic ending, making it, in all senses, a lost world.
While Antarctica is today known as the loner of the seven continents, sharing no natural borders, it used to be much more social, in a sense. Being located higher up and closer to other continents, in fact, for a good chunk of history, it was actually connected to the rest of the world. As for millions of years, it was stuck to South America and Australia, or at the very least, had land bridges with them, allowing many walks of life to use Antarctica as a stepping stone throughout time, including the dinosaurs. And we know this, as researchers have found sauropod skulls in all three continents which are nearly identical to one another, implying dispersion across the three. And along with passing through a variety of dinosaurs and other animals, decided to even settle down into Antarctica, as it was much warmer during the Mesozoic, thanks to a more northern latitude and in general, warmer global temperatures, resulting in the continent having a mean air temperature of about 12° C or 53° F during the Cretaceous, so warmer than many European countries of today, like Germany, for example. Therefore, instead of only having a handful of resilient animals like today, Antarctica had a plethora of dinosaurs, including theropods, ankylosaurs, hadrosaurs, and sauropods. While in the waters, sharks and marine reptiles could be found in mass.
Additionally, thanks to the more negotiable weather and increased precipitation, the landscape was unrecognizable compared to now, being very green instead of white and dominated by expansive rainforests where conifers, ferns, angiosperms, and ginkgos made up the majority of flora. So, in other words, there would be absolutely no way of telling that you were even in Antarctica, and that's even with disregarding the dinosaurs.
But as you probably can tell, dinosaurs, or at least the non-avian kind, are no longer found in Antarctica. And that's because, despite being situated on its own tectonic plate and quarantining itself by drifting ever more towards the South Pole, Antarctica, like the rest of the Earth, still got its face absolutely rearranged, or so you could say, by the dinosaur-ending asteroid, which most likely sent a massive tsunami crashing into its coast and heated up air enough to cook anything caught in the open and creating catastrophic forest fires. Then, even when things cooled down, it still remained a bad situation because while eventually it wasn't on fire, it happened to keep cooling and cooling, thanks to the massive amount of dust, sulfur, and other nasty stuff that blocked out the sun, leading to much of the world and Antarctica freezing over.
However, where people get it wrong is that Antarctica did not remain a frozen wasteland. And not only did it make a comeback, but it reached levels of life not even seen during the Mesozoic. Not to mention that, in spite of the common idea that the Cenozoic, i.e., the current geological era, is cold, Antarctica also became possibly warmer than even before, minus the fire part, that is. Which was all thanks to pretty much the exact opposite of an ice age: a super greenhouse. Following the end of the Cretaceous, temperatures would start to tick upwards, which was a result of the abundance of carbon dioxide being released, but from where is not certain. Nevertheless, this caused major changes to the climate, and the Earth steadily became hotter and hotter, with both a Paleocene and Eocene epoch being much warmer than today. In fact, during a climatic event known as the Eocene Thermal Maximum, one Earth may have been at its hottest point for the last 100 million years. And in Antarctica, you could have seen some unbelievable average temperatures of around 25° C or 77° F, which, just to put that into perspective, is like Kenya today. It also helped that even though it had moved south since the Mesozoic, the continent was still higher up than presently, hovering at around 60° South. This allowed many plants to spread out and colonize the continent that today would not stand a chance. And if you ended up marooned there during most of the Paleogene, you might think you were on a tropical island, as palm trees, swamp cypress, and water lilies would be greeting you instead of icy plains and glaciers.
Now, I wouldn't get your hopes up too high, though, because if you started to explore this lost world, you'd soon realize that it still was not the easiest place to survive, just for all different reasons. Currently, the largest terrestrial animal and predator in Antarctica year-round is a flightless midge, so the size of a small ant. So, nothing too worrisome yet. During those times, it was something far larger and scarier: a dinosaur. No, I am not joking, but I am also not talking about the non-avian dinosaurs, but rather just about the closest thing to one since their demise: a terror bird, scientifically known as Phorusrhacidae. Now, you may be a bit confused, as these guys are notorious for ruling South America, not Antarctica, but that is where the land bridge I talked about comes into play. Because it was still around after the Mesozoic, and the two continents may have stayed connected, at least periodically, up until 40 million years ago, allowing terror birds to come on down and wreak havoc, having large, powerful, curved beaks that could rip and dismember prey, while also having very strong legs which were equipped with giant sickle claws at the end, which allowed them to both pin prey down or poke them, and made these guys just a bit too close to dromaeosaurs for my liking.
Anyways, furthermore, the one from Antarctica, while currently undescribed, was likely one of the worst kinds you could meet, as it highly resembled the Phorusrhacos, an abnormally large, large, and predatorial member that could be the same size as male ostriches, standing around 8 ft or 2.5 m tall and weighing in excess of 130 kilos or 290 lb. So, you know, just about three wolves stacked together. Yet, despite their size, they weren't three times slower than a wolf because, thanks to their leg construction, they were insanely fast, running at speeds over 31 mi or 50 kmph, allowing them to chase down a myriad of prey. And they were probably the undisputed terrestrial apex predators of Antarctica, patrolling the forested areas and any grasslands.
But considering that the largest pure terrestrial animal is now a bug, it does raise the question of what the heck were the terror birds eating. Well, that land bridge with South America did not just bring down predators or birds, but also an army of mammals that we know about thanks to the Letta Formation, which represents present-day Seymour Island and dates from the Paleocene to the Eocene. And given this long time span, not everything found there lived all at once, yet it still gives us a good general idea of what this lost world was like back when it was green. And because the connection was with South America, many of these mammals were the kind you associate with it, not Antarctica, like the Astrapotheria, a now-extinct group of rhino-like mammals, which were herbivorous and among the continent's larger creatures. Though only two are currently confirmed to have lived in Antarctica: the Trigonostylops and the Astrapotherium. Both of them had weird and large specialized teeth, but I assure you that these guys are vegetarians; they just had some weird dentition. And they also widely ranged in size, as while both are at least pangolin-sized, the Astrapotherium has sometimes been estimated to reach over half a ton in certain species. However, this is more speculative. But a much more confident and equally weighted mammal was the Notiomastodon, who might be the largest confirmed land creature in Antarctica since the dinosaurs, with the adult weighing up to 400 kg or 880 lb, so about the size of a modern-day musk ox. And they likely sustained their respectable statures on nutrient-rich flowering plants that were once abundant at the time.
Now, these guys were not members of the Astrapotheria, but were instead the Xenungulata, an extinct order of ungulates that could, in some cases, be quite strange, as best demonstrated by the only other known Antarctic xenungulate, the Victoriolophus. This was a far smaller mammal, but at the same time, a stranger one, as it had high nasal openings, suggesting a possible noodle-like proboscis, which likely operated like the one seen in tapirs, allowing it to grab vegetation that was otherwise unreachable. In recent times, its nasal openings have also been interpreted as a pair of prehensile lips like those on a moose, or perhaps even a weirder nose similar to what's seen in a Saiga antelope, that would have helped it filter dust, cool it down in the summers, and keep it warm in the winters, if need be.
Now, with all this said, while the Astrapotheria and Xenungulata like made up the biggest mammals in Antarctica, they were by no means the only ones. And many other kinds could be found, including undescribed Didelphimorphia, Gondwanatheria, and even Macroscelidea, better known as the saber-tooth squirrels, thanks to their enlarged teeth, who were also possibly the continent's most dominant insectivore and one of its oldest residents, seeing that this group had been around during the K-Pg extinction event and had managed to survive, likely thanks to their smaller bodies and diet.
And then, to finish it all off, you had yet another unexpected face: marsupials. When you think of a marsupial, you probably picture this, or this, or even this. Basically, all Australian animals. And while they may have made a good home there, they actually first evolved in South America, and thus leading to their presence in Antarctica, where it is there that they actually moved on to Australia because, like I mentioned, the two continents were connected as well, at least for a part of the Cenozoic. So far, three groups of marsupials are known to have made it down to Antarctica: the Didelphimorphia, Paucituberculata, and Microbiotheria. Unfortunately, almost nothing is known about the first group, but we do know a bit more about the second one and understand that they were quite diverse in appearance and could fill many niches. Meanwhile, the third group, Microbiotheria, we actually know quite well, seeing that they are still living, albeit not in Antarctica, with the sole extant member being the Monito del Monte, meaning "little monkey of the mountain" in Spanish, and it can be found in Argentina and Chile. Interestingly enough, though, these guys are more related to Australian marsupials than its fellow South American ones, but that's besides the point. With the real point being that marsupials and many traditional ancient South American mammals are what largely made up the Antarctic environments, and thus supplying more than enough food for their terror bird overlords.
And it wasn't just birds that mammals had to watch out for, as another carnivore made these lands home too, in the waters, for that matter, which is one that you would never imagine in Antarctica today: crocodiles, or at the very least, some kind of crocodilian. For a long time, paleontologists have guessed that crocs lived on the continent, given its land bridges and previous temperatures, but they never actually found anything conclusive until the discovery of a giant osteoderm dated to some time in the Eocene that exactly match those seen in both living and extinct crocodilians. Therefore, we know it was a croc, but what kind is uncertain. But what we do know is that it was a giant, as the osteoderm in question was about the size of one you'd expect to find on a 23-ft or 7-m long croc, so about 15% bigger than the largest saltwater crocodile ever recorded and about 35% greater than the average one. So, this would technically give the crocodiles the title of the largest predators on land, if we were including semi-aquatic creatures. Furthermore, they were likely opportunistic ambush hunters that dominated freshwater environments, potentially inhabited brackish and even saltwater too, kind of like how the saltwater crocodiles can today, which would have of course brought them into contact with many mammals and made sure that you could never remain completely safe when you went for a drink, especially since its large size meant that absolutely nothing was completely off the menu.
And interestingly, but perhaps not surprisingly, evidence shows that this mysterious reptile was not alone, as other fossils located not so far away imply that there were also crocodiles in the area that were more specialized, namely possessing piscivorous diets. But again, not much else is known about this croc either, though it does tell us that when Antarctica was green, virtually every animal could expect to be eaten by a crocodile at some point.
And this included a very familiar face, who is actually the only animal I brought up so far that still lives in Antarctica: penguins. Now, we typically pair these guys with the cold, so it may come as a surprise that they were still around back when Antarctica was much warmer, and it was in the heat that penguins actually got their start, as they probably evolved off the coast of warm Australasia and New Zealand around 60 million years ago and then made their way to Antarctica, where they then thrived. And if the continent is considered a penguin paradise today, then it was an absolute penguin heaven back then, because now only two penguin species call Antarctica their full-time permanent homes, yet during the Paleogene, this number was more like 16, with each one being a bit different from the last. Yet, it wasn't just the numbers that were surprising, but also their diversity and size, as prehistoric penguins were absolute units. With three of the 16 species being what scientists call giant penguins. Presently, the largest penguin on Earth is the Emperor Penguin, which can be 100 lb or 45 kilos and stand at a maximum of 4'11" or 1.5 m, which is definitely impressive, in all, but is still an absolute small fry compared to two of the ancient giant penguins, specifically Anthropornis and Pachydyptes. Both of these guys were titans who, at their biggest, could have stood at around 6'9" or over 2 m tall. In other words, taller than Michael Jordan. And they were heavier too, thanks to their robust builds and blubber, with adults weighing 108 kilos or 238 lb, and the Pachydyptes could be even bigger, weighing 116 kilos or 256 lb. So, in other words, we're talking about a penguin larger than a jaguar. So, you already know, being slapped by one of these guys most likely hurt. And they were also pretty nifty in the water, likely being able to hold their breaths for over 40 minutes, and thus allowing them to wreak havoc on squid, fish, and krill.
Now, you might be thinking, why were they so big? And the answer is, it's thought their giant sizes may have been for energy conservation purposes. But even with their size, it still wasn't enough to ward off crocs if they swam into one, nor did it likely stop the other nightmares that patrolled the coasts. And what were essentially the times: mosasaurs, cetaceans. Obviously, there are still whales in Antarctica today who can definitely be a bit scary in their own right, but the Paleogene ones were somehow both scarier and even bigger too. With two genera being known of so far from the Llama Formation: the first one was almost certainly an apex predator, as it was an undescribed basilosaurid, who were typically large, serpent-like, and specialized to be predators in shallow waters, coming equipped with massive skulls and equally giant teeth that could easily penetrate skin, muscle, and bone. And based off of at least one located mandible, it's possible that this enigmatic basilosaurid might have measured up to 40 ft or 12 m long and most likely fed upon anything the right size that it came across, which might have included now-giant extinct sea turtles that once reached up to 10 ft or 3 m long, so bigger than any turtle we have around now.
And while not as predatory as the basilosaurid, you also had the Lanthanocetus swimming around too, a whale who visually could be even more terrifying, as its remains imply that it was absolutely colossal. For now, we only have the bones of a juvenile, but here's the thing: this juvenile was freaking massive, being about the same size as the largest known adult orcas. So, who knows how big the adults got? But just going off of what we know about modern-day whales, it most likely rivaled humpbacks in size, depending on just how old the youngling was. And this is terrible news, as these guys were likely much more bloodthirsty than humpback whales. Despite though also being baleen whales, you see, back in the day, baleen whales actually still had teeth, and this extended to Lanthanocetus. You could use them for oral behavior or to help trap prey as its suction fed, since its facial construction was a bit like that seen in modern-day beaked whales. There's also a chance that it was a hybrid predator, both hunting and using suction feeding, leading to a very diverse diet where almost nothing was safe, which is only further emphasized by its presence in both river deltas and the open ocean. So, given its size, it could have snacked on a variety of fish, penguins, cephalopods, and even sharks.
And actually, lots and lots of sharks, because opposed to today, prehistoric Antarctica had an exhausting list of sharks. I mean, it was in some ways the Australia of the Paleogene. And so, some of the groups you could find included requiem, goblin, gulper, carpet, kitefin, longnose, school, seven-gill, six-gill, hound, poor beagle, smooth hound, sand angel, and saw sharks. Yeah, I did tell you it was exhausting. And even this wasn't the full extent, as you had three more interesting residents too, such as an extinct species of basking shark, the Megachasma, that was possibly the ancestor of mako sharks. And then, the most fascinating, or perhaps terrifying, of all: the Megalodon. Well, actually, not 100% the Megalodon, but basically, as these were actually two species that belong to the same genus that the Megalodon did, the Otodus, meaning "ear-shaped tooth." Specifically, researchers know that Otodus avi and Otodus cuspidatus prowled the coastal waters of Antarctica, where they were apex predators and presumably came into conflict with the coexisting giant whales, as these guys could be absolutely huge. The smaller of the two was the avi, which had finer serrations than most Otodus and typically grew to be 6 m or 20 ft long, so still pretty big and about the size of the biggest great whites in the oceans today. Now, the cuspidatus was far bigger, with the largest specimens measuring 9.5 m or 31 ft, so not as long as its cousin, the Megalodon, but still large enough to ensure its place as a top predator. And based off what we know about the Otodus in general, we can assume that these two likely fed on fish, turtles, other sharks, and possibly even whales. Their presence, along with the rest of the sharks, made prehistoric Antarctica's waters deceitfully deadly compared to now, and a chaotic place for penguins and really anything else that called the waters home.
But penguins weren't the only birds that had to live on edge, as a huge number called the area home. And birds' success in Antarctica through the Paleogene actually tells of an interesting story, as some paleontologists believe that it was actually here that the first modern bird ever evolved: the Avis. Now, this bird never made it out of the Mesozoic, but its presence on the continent represents just how important Antarctica was for bird evolution. What's more is that some also think that birds mainly survived in Antarctica following the asteroid, and thus possibly explaining their large numbers and high diversity. And thus far, we know that falcons, ibises, albatrosses, and petrels were all present at the time. Plus, you also had the strangest bird of them all, who happens to be the only one now extinct: the Pelagornis. It was a member of the Pelagornithidae family, who were hard to miss thanks to their odd teeth, or at least what looked like their teeth, as these birds in truth did not have any teeth at all, but rather bony projections from their jaws, which just looked like them and gave them a rather freakish appearance. It also didn't help that most of the members of this family were massive, Pelagornis included, with an estimated wingspan of about 16 and 20 ft or 5 and 6 m, so, you know, just akin to the wingspan of a small plane. Or if you prefer pterosaur analogies, it was about the same size as a Pteranodon. Not to worry, though, because in spite of its appearance and size, the Pelagornis was a bit of a softy, literally, with its fossils being abnormally fragile, which in life most likely kept it restricted to just hunting fish and squid, which it did by skimming the surface of the waters and sniping any unfortunate prey that was too close to the surface.
And there you have it. Before the ice, Antarctica was a chaotic but vibrant world full of strange and terrifying animals. Which leads us to our final question: where did they all go? And sadly, the answer is not a pleasant one, as most of the continent's inhabitants met a fairly tragic ending. With this tropical party having come crashing down during the final days of the Eocene. And if you somehow found yourself in Antarctica at that point, you'd be guaranteed a pretty grizzly ending, unless that is, you were a very lucky penguin or bird. And it almost seemed as if Mother Nature had a vendetta against the continent, as everything that could go wrong did, and did so pretty much all at once. The exact timeline is blurry, but it may have started with the continent completely separating from the rest of the world, and thus creating the Drake Passage between it and South America, and the Tasmanian Passage with Australia. This isolation meant that any animals on the continent were now stuck, which is not necessarily a problem within itself, considering that Antarctica is quite big. Yet, the issue is that as this problem arose, so did another, much more troublesome one. For over 200 million years, the Earth had been pretty warm, and at times very hot, and then rather abruptly, this all started to change about 34 million years ago, when temperatures just started to plummet. Which, ironically, is possibly thanks to Antarctica's isolation, because as the passages opened up between it and its previous neighbors, it led to the formation of the Antarctic Circumpolar Current, a major current of cold water that surrounds Antarctica even today and blocks warm waters from reaching the coasts while also absorbing carbon dioxide. This, in addition to its southward movements, resulted in the first ice sheets starting to form and marking the onset of the Late Eocene Ice Age, which, by the way, we are technically still living in. The bitter cold weather that would have accompanied these events ultimately eradicated most of the native life, with the changes being just too rapid for most to adapt, while the ice itself caused habitat loss on an unprecedented scale. Although it wasn't the end of the story yet, as the continent still had areas without ice sheets where the last survivors could have sought solace. But the relief, like many things, was only temporary, as over the next 7 million years or so, the continent slowly succumbed to the ever-expanding ice until it was virtually covered. Then, of course, to add salt into the wound, the effects of the cold only worsened as these ice sheets grew, since they reflect massive amounts of heat from the sun. And as you can probably figure out, the continent has remained in this perpetual icy state, mostly unchanged. And while we do have the Llama Formation, there is no telling what could be hidden beneath all the ice in the rest of the continent, although honestly, to find that out would probably require a lot of pain that I, at least, would rather avoid. Thanks for watching, and until next time, OnxZoo.