|
Just bobbing alongside a kronosaurus insisting "it looks like you're trying to wrote a letter"
|
#
?
Apr 13, 2024 23:15
|
|
|
|
| # ? May 6, 2024 12:22 |
|
|
Time for another effortpost! This time its on Pleistocene Australia.  Yeah nah mate, first some context, I'm going to try and keep this post a little more pared down compared to my South America post, which was mostly around the Miocene. Luckily Pleistocene Australia is a bit less broad.  It's actually not quite right for me to use the term 'Australia', which is mostly just the contemporary continent and its outlying islands, during the Pleistocene (which most people would probably think of as 'The Ice Ages', though that's a bit vague, starting 2.6 million years ago, ending 11700 years ago) the massive amount of additional water locked in expansive ice sheets compared to today meant that sea levels were much lower, on the order of 130 meters or more during the Wisconsinan glacial period from about 75000 to 11000 years ago. The result of this, as can be seen in the map above, is a huge amount of additional land area compared to today as what are now shallow seas were then dry land. The difference was most pronounced in areas that currently now have big stretches of shallow sea in the continental shelf, in Northern Europe this mean the North and Baltic seas essentially did not exist at all, and Britain and Ireland would have been impossible to make out from a general blob of land in the North, but in the Asia/Pacific region the difference was at least as prominent. The Yellow sea was dry land, Japan was connected to Korea and Siberia, almost the entire Indonesian archipelago was connected to the mainland in a large peninsula called 'Sundaland' and most importantly for our story Australia, New Guinea, Tasmania and a slew of surrounding islands were mashed together into a much larger continent called Sahul. The erasure of the Bass Strait, Torres Strait and Arafura sea meant that animals could freely range over this entire area with no barriers, and altogether the landmass could balloon up to more than 10.6 million square kilometres in size, compared to current day Australia's 7.6 million square kilometers. This is one of the reasons there's a lot of continuity between the wildlife between places like Cape York peninsula and Southern New Guinea, it was all part of the same landmass until a few tens of thousands of years ago.    As you can see from the first map above Sahul had generally a similar climate to modern Australia, with a massive desert in the centre bearing west, and as it went further north and east the rainfall would get heavier all the way to true rainforest that dominates New Guinea today. But as you can see from the second map, this landmass even at the height of the ice ages and lowest possible water levels was still completely disconnected from South East Asia by a series of extremely deep fissures. These trenches still exist today and are absolutely crucial in understanding the biogeography of Oceania compared to Asia, the Wallace Line is the most famous division and was noticed by Alfred Russell Wallace as the the marker that distinguished fauna and flora that was primarily Asian in origin from that which was primarily Australasian. Animals can't readily cross these barriers which has ensured a large amount of isolation for Australia and New Guinea compared to the rest of the world. Much like South America Sahul became an isolated continent after the break up of the southern megacontinent of Gondwana in the Cretaceous, as you can see in the third map, which depicts the southern hemisphere from about 40 million years ago, it was last connected to Antarctica at a much more southerly position and since breaking off has travelled north, totally isolated from everywhere else to the modern day, unlike South America. The Isolation of Sahul has famously lead to a lot of bizarre animal life since it is so disconnected from the goings on elsewhere and its creatures have been allowed to evolve independently since the K-Pg extinction. We all know and love Australia as the land of marsupials and a lot of poisonous animals. As I've touched on the South America post, contrary to what people tend to think Marsupials aren't actually purely native to Australia and can be found in both of the Americas today, but they certainly are much more dominant in Australia compared to placental mammals. Historically, before human interference, the only placental mammals that could be found in Australia are bats (who could simply fly there) and a number of rodent species that managed to raft across the bodies of water mentioned above (like they did from Africa to South America in the last post), who are collectively known as 'Native Rodents'. These animals occupy their typical niches of insectivores, nectarivores, granivores and stuff like, with a couple of additional unusual niches that some of them have occupied, like the Rakali pictured below, which has taken on a niche more akin to a small otter than a rat, eating fish, crayfish and other freshwater creatures. Australia and New Guinea are considered a hotspot for bat diversity, with all kinds of species from big flying foxes to tiny little vesper bats.   With placentals mostly restricted to these small roles, Australasian marsupials have had the room to go hog wild and occupy the wide variety of niches typically occupied by placentals everywhere else, from big dominant ground herbivores, to tree dwelling monkey or sloth like niches, to the major predatory roles and beyond. Australian marsupials are overwhelmingly part of the superorder Australidelphia, which somewhat infuriatingly actually has one of its members (the Monito Del Monte) all the way over in South America, just barely ruining the neat divide between American and Australian marsupials. Whatever the case, Australidelphia has a wide variety of subdivisions like Dasyuromorphs (mostly carnivorous animals like Tasmanian devils and Quolls), Peramelemorphs (Bandicoots, whose ability to break boxes by spinning into them I have yet to determine), Vombatiformes (Koalas and Wombats) and Macropods (Kangaroos and Wallabies). There's a lot of convergent evolution apparent between marsupials and placentals, probably most noticeable in the Marsupial Mole which, despite having no close relation whatsoever, has hit upon an almost identical body plan and appearance to the African Golden Moles. Both are pictured below and I'm going to challenge people to tell me which is which, just keep in mind that the Golden Mole is more closely related to elephants than the Marsupial Mole, which itself is more closely related to the Tasmanian Devil than it is to the Golden Mole, good luck!    All of these living animals are all well and good, but anyone and their uncle knows what a Kangaroo or Koala is, we're here for the dead stuff! During the Pleistocene the inhabitants of Sahul used to be more prevalent, occupied more niches, and reached much larger sizes. Kangaroos are well known today for being the biggest living marsupials, but in relatively recent history they used to have a much larger cousin, Procoptodon. Compared to modern Kangaroos this animal was considerably heavier and taller, a red kangaroo maxes out at around 90 KG and 1.8 meters tall. Procoptodon could reach heights of 2 metres or more, but could weigh potentially up to 250 KG, making it about the size of a big Red Deer today. This animal was part of a slightly different lineage than living Kangaroos, the short faced kangaroos, and its diet was probably more specialized for eating tough shrubbery and leaves, with the shorter face having bigger muscles and jaws for chewing and more developed hands for pulling down branches. It also notably only had a single toe on each foot instead of having two or three as is the norm with modern kangaroos, and it seems as though it didn't hop, instead its skeleton was more built for running normally.   Macropods have been important animals for a long time, taking on herbivorous niches usually dominated by the likes of deer or antelope elsewhere especially as wider grasslands emerged as Australia got drier since the Oligocene, and they aren't just limited to Kangaroos with most of the species being some variety of Wallaby. Protemnodon seems to have been another offshoot, similar in appearance to living wallabies but much larger, up to 170 kilos, and I've heard rumours that there might have been another species of kangaroo that was even bigger than Procoptodon, but I can't find any real info on that.  Of course, kangaroos aren't completely tied to the ground, though less well known compared to their relatives there are a number of species of tree kangaroo that live, if you can believe it, in trees. Tree kangaroos are much more common in New Guinea than Australia today, because they have a lot more forest to work with on the island, taking on a lot of roles associated with things like monkeys elsewhere, and they can get surprisingly big, up to 15 kilos in some species. But the extinct species could get much bigger, specifically those in the genus Bohra, which could get up to 45 kilograms and lived in a wider habitat in mainland Australia than their living relatives do.    In addition to these big Macropods, we have the Vombatiformes. Today they are limited to three species of Wombat, and the Koala, but in the recent past this group used to be much more diverse. The most famous member is an animal called Diprotodon, as far as we can tell this was the largest marsupial that ever lived, a genuine behemoth that could reach more than three tonnes and more than four metres long, this dominated the Pleistocene landscape of Australia and probably had a considerable effect on its environment as a major herbivore. Like rodents it possessed incisors that never stopped growing, keeping them pared down with its diet of tough plant matter, and possessed a very powerful bite if it needed it. Interestingly, we also have evidence that these animals were strongly migratory, one of the few marsupials that did this, based on isotope ratios in the teeth that match different locations, implying that they had a seasonal cycle of movement based on rainfall and food availability.   Diprotodon is the best known of its kind, but there were other members of its family filling in other niches, Zygomaturus was smaller but still formidable, probably over half a tonne, and seems to have been more restricted to forests compared to the much more free roaming Diprotodon, it might even have had an aquatic lifestyle. All marsupials have lower metabolism than placentals, which might assist them in growing to large sizes on the more marginal land of Australia. Hulitherium meanwhile lived in the mountain forests of New Guinea, and was much smaller than its titanic relatives, probably maxing out at 200 KG, but with a posture more suited to upright stance and a diet likely consisting of a lot of bamboo, almost like a Giant Panda alive today.   Another large Vombatiforme, probably the second largest marsupial after Diprotodon, is Palorchestes. This might have weighed up to a tonne, and seems to be another example of an animal converging on a ground sloth style bodyplan and lifestyle, with large claws it could use to strip bark and pull down branches, a tendency towards bipedalism, as well as good evidence it had a very long and supple tongue to grab food as well. Previously scientists also thought it had a short trunk like a tapir based on the shape of its skull, but it seems it actually had extremely flexible lips that let it grab food as well, just all in all a very weird looking creature.   Although things like Diprotodon are often colloquially called 'giant wombats', they aren't really wombats and the name is better reserved to an actual giant wombat called Phascolonus, that could weigh up to 200KG (compared to living species of wombat that don't go bigger than 40 KG). There actually used to be number of other wombat species around Australia, including Sedophascolomys, larger than living wombats, that were knocking around Australia before going extinct at the end of the Pleistocene.   Just because its hard to slot them in anywhere else, I may talk about Monotremes, egg laying mammals highly divergent from everything else, 'primitive' if you will even though they are doing fine in their roles today. In contemporary Australia the Platypus is well known and we have fossils of their extinct relatives like Obdurodon pictured below, from the Miocene that still retained teeth and could get more than a meter long. You also have Echidnas, 'Spiny anteaters' that take on the role of things like Anteaters in the Americas or Pangolins in Eurasia and Africa. Extremely ancient representatives of this group going back to the Cretaceous have been found in Australia, Steropodon is the earliest member 100 million years ago, but closer to now you also had the largest Monotreme known, Murrayglossus, a giant Echidna that could weigh up to 30 kilograms, twice the size of the living Long Beaked Echidna that lived in Western Australia in the late Pleistocene.    So far all of these animals we have focused on have been mammals, but Australia is one of the most the best suited places on earth for reptiles, while also being famous for its birds, and accordingly both groups had a major role as part of the megafaunal assemblage in Sahul. To keep on track of the major herbivores in the region, we once again return to the bizarrely recurring phenomenon of 'Heavily Armoured animal grows really big and gets a spiky tail it hits things with', that we have previously seen in Ankylosaurs and Glyptodonts, in this case with Meiolania and its close relative Ninjemys (btw, yes, that name is exactly the reference you think it is). These were particularly large and very spiky turtles, with horns covering their heads and all over their tails that they could have certainly used as weapon, probably mostly against sexual rivals. They are among the larger known turtles, reaching weights of more than 200KG and a carapace length of about 2 metres. They probably couldn't pull their heads into their shells with all of the extra spikes, but at the same time likely did not need to with all of the sharp, pointy protection.. Meiolaniidae have an incredibly confusing evolutionary history and distribution. All of the most recently known forms are from Oceania, but they had relatives all the way over in South America (where else?) up until the end of the Eocene and the clade in general seems to have been very old, going well back into the Cretaceous. They may have even made their way to Australia in the first place via a route from South America through Antarctica, which is bizarre for a reptile. Moreover, they seem to have dispersed across various islands in the South Pacific, species of Meiolaniidae have been turned up in New Caledonia, Fiji and Lord Howe Island, how they did this is anyone's guess, the most popular explanation is that they accidently floated to the islands when washed out and managed to establish themselves there (tortoises are quite good at doing this), others think they might have already been on these islands before they broke off from the mainland, possibly involving the sunken continent of Zealandia with some species potentially having been from New Zealand, as if they are loving Chelonian Atlanteans. Its all very hard to put together, and upsettingly, compared to most of the other animals here, Meiolaniids came incredibly close to surviving to the modern day on their island hideouts in the Pacific, potentially making it to less than 2000 years ago, until they all died out and denied us any answers.     Big turtles are one thing, but big birds are another, Australia and New Guinea are already replete with giant, flightless ratites in the form of Cassowaries and Emus, but they also used to host an entirely different family of much larger flightless birds called Dromornithids. Despite what would seem obvious, these birds don't seem to have been close relatives to the living giant flightless birds of Australasia today, at all, in fact they were probably more closely related to waterfowl and another giant extinct bird called Gastornis. If this sounds familiar, its because its very similar to another bird I mentioned in my South America post, Brontornis, which also is a giant flightless bird that is argued to have a close affinity with waterfowl and Gastornis in particular. Like Brontornis, some of the Dromornitids could get ridiculously big, Dromornis Stirtoni takes the gold in terms of pure size, although this was not a Pleistocene animal. It potentially weighed up to 500 kilos and exceeded 3 meters tall, making it a contender for the largest bird ever. Even like Brontornis there is some controversy about its diet with some scientists pushing the idea that it could have practiced various forms of carnivory with its massive beak, though the current consensus suggests that these birds were probably herbivorous.  That's all well and good, and certainly I would not have started a fist fight with any of these animals, but to pull things back to the Pleistocene, the last known Dromornithids was a beefy customer called Genyornis, otherwise known as the Mihirung. Although not quite as big as its older relatives, it was still massive, at 220 Kilos and 2.2 metres tall, it almost certainly would have encountered the first humans to set foot on the continent, who probably also meant their doom.   So having covered most of the major herbivorous animals in some capacity, we are inevitably at the bit everybody has been desperate to get to, the bit about the animals that ate the herbivorous animals we just covered. No offense to things like Genyornis or Diprotodon, I don't meant to suggest they are simple buffets for the animals people actually care about but... uh, well sometimes it can be hard to get away from that sense of how people see things, and Pleistocene Sahul seems to have already stuck in a lot of people's minds for its collection of dangerous predators, in addition to all of the still extant poisonous snakes and such make Australia such a heavily memed subject. We better get the most obvious one out of the way, Megalania... or is it Varanus Priscus? There's actually some controversy about the naming for this animal, to the best of my understanding, under standard nomenclature in zoology Megalania is no longer a valid genus name and officially the animal is just within the Varanus genus with the name Priscus, but scientists yield that the name Megalania has already entered common nomenclature and likely won't be going anywhere, so I'll just stick with that. Megalania is a Varanid, aka a monitor lizard. Monitors live all across Asia, Africa and Australia and are probably the most intelligent and active lizards in the world, they are also the largest and most heavily adapted towards top level carnivory. In Australia today you find a number of monitors including the massive Perentie, while up in New Guinea you can find the Crocodile Monitor, another big species. The Komodo Dragon is famous as the largest lizard on earth, as big as 80 kilos and capable of brining down animals as large as Water Buffalo. Komodo Dragons have highly limited range today to a few islands in Southern Indonesia, but during the Pleistocene they seem to have had a much wider distribution, including in Australia where they probably would have made up one of the major predators.   Megalania on the other hand was titanic even compared to its relatives, unfortunately we don't have very good material for this animal to make a precise call on its size, it actually seems to have been quite a rare animal altogether, so size estimates vary wildly, based on what living monitors are being used as a reference. Some of the estimates from the early 2000s go down as low as about 80 kilos and 3.5 metres, while others pushing it up to a stupendous 7 meters and weight of 1900 kilos! The first estimate was given by a guy called Stephen Wroe in 2004, but since then he's revised his work and came to the conclusion that these fellas could reach a length of at least 5.5 metres and a weight of over 575 kilos, which comfortably makes it the largest land lizard ever (the much larger Mosasaurs are marine and are lizards), and probably the biggest predator running around Pleistocene Australia. Considering how Komodo Dragons already can take down things like Water Buffalo, Megalania was probably capable of preying on things as large as Diprotodon.   Monitors, as mentioned, are more active and have adaptations towards aggressive carnivory compared to other lizards. Their metabolism is higher, which allows them to keep up with fast prey, and they have the ability to breath while running, otherwise not a thing most reptiles are capable of doing, which gives them much more stamina. They have big, sawlike teeth that are very good at lacerating their prey and causing massive blood loss, which is very good when attacking animals larger and faster than itself since even if they get away from the first attack the damage will probably just cause them to collapse over time. To top it all off, in recent years it has been shown that monitors and the Komodo dragon in particular are actually venomous as well, and in addition to the slashing bite they are injecting poison that helps kill their prey quicker, we can't tell for sure if Megalania was venomous, but since it seems that its close relatives are then we can infer it probably was, which might make it the largest venomous animal ever.  Monitor lizards are one thing, but Australia is also very well known for its crocodiles, and back a few tens of thousands of years ago this would have been even more apparent. The living Freshwater Crocodile and Saltwater Crocodile are well known residents of Australia's waterways, with the latter being the biggest living Reptilian carnivore, and of course these animals were alive during the Pleistocene too, and New Guinea also has its own species of Crocs. In addition to this, during the Pleistocene there was another species of crocodile called Paludirex, that seems to have been comparable in size to Saltwater crocs but was more robustly built, like the Indian Mugger crocodile, better adapted to hunting big prey on the water's edge.  Meanwhile, on dry land, a curiously familiar story was playing out with a group of crocodilians becoming adapted towards fully terrestrial life as major carnivores. Unlike the Sebecid crocs in South America that gave us the likes of Barinasuchus, these animals were from a different lineage that as far as I understand were fully seated within living crocodilians, the Mekosuchinae (this also included more aquatic animals like Paludirex). Their most famous member was Quinkara, which like the Sebecids had evolved cutting teeth and was a major land predator, though it wasn't as large in Pleistocene as Megalania, average about 3 metres and maybe 200 kg (though a Pliocene species much earlier probably reached 6 metres). There's actually a bit of controversy about whether or not Quinkara still had some ties to the water, it might have still spent a fair bit of time in and around aquatic environments even while being better adapted to hunting out of the water, personally I think it was much more terrestrial than aquatic.  Quinkana died out probably around 10k years ago, lasting longer than other Pleistocene megafauna, but Mekosuchids persisted for a while longer on island like New Caledonia and Fiji for a while, along with the last surviving Meiolaniids. The last of these crocodilians was a curious animal called Mekosuchus, which was a small crocodilian that has been controversially suggested to be one of the only crocodiles to evolve towards living an arboreal lifestyle in trees. It lived alongside a large flightless bird called Sylviornis, all of these animals probably went extinct when humans arrived a few thousand years ago.   Speaking of birds, it would be remiss of me not to mention Dynatoaetus, a huge eagle that was discovered recently which was probably twice as heavy as the living wedge tailed eagle, up to 12 kilos, and capable of hunting big prey, possibly specialised for forests like modern Harpy eagles and eating things like tree kangaroos.  The last carnivorous reptile worth mentioning is the giant snake Wonambi, this was a big constrictor snake about 6 metres long, comparable in size and likely lifestyle to a large Python or Anaconda.  All this talk about the cold blooded denizens of Sahul might give the impression that the predatory niches were monopolized by lizards and crocs, but this was absolutely not the case, within the marsupials there are several different lineages that evolved towards hypercarnivores roles and became major predators. Of the living marsupials the most notable ones are Dasyuromorphs, as mentioned above. These entail most of the living carnivores marsupials such as the Tasmanian devil, Quolls, Dunnarts, the termite eathing Numbat, and the very recently extinct 'Tasmanian Tiger', AKA the Thylacine. Of the living animals, the Tasmanian Devil is the biggest and most notorious, being extremely aggressive and possessing an extremely powerful bite considering its relatively small size of about 8 kilos, able to prey on animals quite a lot bigger than itself like wombats but preferring carrion when possible. Devils used to be a lot more widespread across mainland Australia but they went extinct there a few thousand years ago. Quolls meanwhile still live on the mainland and are more akin to a small mustelid.    To focus back on the extinct animals, the Thylacine is one of the famous extinct creatures on the planet, so much so that its essentially turned into a cryptid for regretful Aussies wishing they hadn't shot them all back in the 30s for the sake of a few loving chickens. Like the Tasmanian Devil it used to exist across continental Australia, and also New Guinea, before being restricted to Tasmania when westerners encountered it. Its convergent similarity to canids has always been a source of curiosity, and it was a lot larger than the devil, weighing up to 20KG. Like the Devil, it had a very, very powerful bite force for its size, and preyed on larger animals like Wallabies and Emus. Having said that, the Thylacine's actual specialization in large prey is disputed, it might have mostly focused on medium sized animals in a role comparable to a jackal or fox, which would make sense considering the obvious similarities, but then the powerful bite might have let it punch above its weight. It was probably a mid tier predator in the Pleistocene ecosystem, along with Devils and Wedge Tailed Eagles they would have eaten a lot of carrion and smaller animals available across Sahul.   Its kind of weird being able to post actual photographs of an extinct animal like that, hopefully we will get more photos in the future if science can resurrect these creatures, but Dasyuromorphs like the Thylacine are only some of the carnivorous marsupials around during the Pleistocene, the largest and most powerful meat eating marsupials were actually from a completely different lineage that has utterly baffled scientists, Vombatiformes, leading to the infamous Thylacoleo Carnifex, or as some people like to dub it, the 'Marsupial Lion'. Thylacoleo is a very unlikely animal to become a major predator, as mentioned its more closely related to living wombats than it is to other carnivorous marsupials, its ancestry was probably from an animal that was an obligate herbivore that switched hard into hypercarnivory for reasons we'll never really know. The lineage of this family, Thylacoleonidae, goes back to the late Oligocene, with Thylacoleo being the last and largest known member of the family.   Its the teeth that really make this animal so loving weird, which is probably why every Paleoartist makes sure its showing them off. As you can see from the skull below, they've basically gone for an entirely different arrangement from almost every other synapsid carnivore in the last 300 million years save for Whales, if they count. Instead of using the canines as the main killing and cutting tools, they've shrunk down to virtual nubs, and in their place its the incisor teeth that have been enlarged into these massive daggers. Meanwhile, the only other large teeth they have are a pair of hugely enlarged premolars that they've turned into carnassial shearing surfaces, presumably to cut the meat off their meals. To try and get across how strange this arrangement is, I've put a picture of Thylacoleo's skull alongside that of a tiger skull, a wolf's skull, and the skull of a long extinct cynodont called Cynognathus that was also a big synapsid predator that was probably close to the ancestors of all living mammals 240 million years ago:     Thylacoleo's dentition and lineage are so strange that for a long time, many scientists refused to believe it actually was a carnivore, suggesting weird ideas that these teeth were all evolved to eat massive fruit, but there's really no argument that it was a carnivore, and moreover very good at being a carnivore. The bite forces calculated for this skull are absolutely obscene, its been determined to have the strongest bite force, pound for pound, of any mammal in history, these weren't small animals already, a good sized Thylacoleo was comparable to a Jaguar or small Lion, upwards of 130 kilos, but it had the same bite force as a large lion more than twice its size. This has lead to the conclusion that it was probably hyper-specialised in hunting large game, its bite was so strong that it could kill a big animal like Diprotodon or Procoptodon much faster than a living lion could for comparably sized prey, and it was a rather bulky and slow animal poorly placed to try and chase small game but very good at getting the drop on much larger animals and killing them quickly. We also know that its forearms and claws are very well developed, leading to theories that it might have hunted by dropping down from the trees to get at unsuspecting large animals from above and dragging the carcases up into trees like Leopards tend to do, as well as using its huge claws to get firm leverage on big animals to deliver the killing blow. While Megalania gets a lot of coverage and interest among the public, as far as I can tell Thylacoleo's remains are actually much more common compared to the much rarer lizard, these animals were probably the most dominant carnivores in Pleistocene Sahul and I suspect that they were probably terrifying things for the first humans in the region to encounter.  And encounter they did, basically all of these animals we have touched on today would have met the first Australians. The entrance of the first people into Australia and New Guinea has been, like almost everywhere else, the source of extreme controversy, but increasingly we have evidence that people arrived much earlier than we used to think, some estimates put the first human arrival on the order of 60000 years ago, with the major megafauna starting to go extinct around 40000 years ago. I don't want to get too deep in the debates about this, there's a tremendous amount of controversy of why these animals went extinct, but to put my cards on the table I strongly suspect that human influence was probably the most important factor that caused these creatures to meet their end, either through direct hunting and competition, or the use of new technology and techniques like fire stick farming that probably had big impacts on the wider landscape. The drying environment of Australia likely also would have put a lot of pressure on all of these animals, making it harder and harder to eke out a living alongside the new arrivals, for the likes of Diprotodon it would have meant a long term decline until final termination, and the carnivores that depended on them would have followed soon after. Today Australia has no native land animals above 100KG, but even still we can see what might be fascinating little glimpses across these huge gulfs of time at the memories of these beasts, with suggestions that indigenous oral histories preserve some memories of things like Diprotodon or even that Thylacoleo and Thylacines are depicted in extremely ancient rock art.   Anyway, I hope everyone enjoyed that, its a hell of a thought that people just like us actually encountered and lived alongside these creatures for an extended period of time. I want to give a particular recommendation to Nellie Pease for a lot of the paleoart, she's the one who did all of the illustrations of the adorable cockatoo interacting with these ancient animals, which I think is just such a genius way to link them to the present day Australia. I was also able to get a lot of the art from Nix Illustration again, in addition to the excellent Peter Schouten. The next effortpost I make will probably be on the seas of the Pliocene, especially off the coast of Western South America, the infamous haunt of the giant shark Megalodon, but there's a ton more to talk about the whole ecosystem that I just find fascinating. khwarezm fucked around with this message at 18:42 on Apr 22, 2024 |
|
#
?
Apr 14, 2024 16:27
|
|
|
Op, you know a lot of poo poo. What do you do? Are you a paleontologist? Or is this just something you're really interested in?
|
|
#
?
Apr 14, 2024 18:48
|
|
|
Absolutely losing my mind at the cockatoo in every drawing, it's so cute
|
|
#
?
Apr 14, 2024 20:52
|
|
|
wesleywillis posted:Op, you know a lot of poo poo. Nothing of the sort, I just have an interest, there's a lot of information on the internet these days compared to how things used to be when you have so many blogs, news sites, podcats, youtube channels, etc, even Wikipedia on its own is a much better resource than it used to be. It helps that you can find a lot more information now because there's less of a singular focus on dinosaurs and particularly North America than I would have to put up with from books and stuff when I was young, as you can tell from my posts I find the Cenozoic and Paleozoic more interesting just because they are less talked about, especially the places with biota more divergent from the usual stuff you see in most of the world. Its interesting how learning more about a wider variety of things across a greater time period and area deflates the old things you used to read, a good example of this is one of the common things I used to read when I was a kid, that Sauropod dinosaurs declined during the later Cretaceous, this is really not true at all and is the result of what seems to be a specific phenomenon where they went extinct, for a time (they show back up just before the K-Pg extinction) in North America specifically, and had a bit of a drop of diversity in Asia. Because popular palaeontology is so skewed towards North America for various reasons, especially going back before the 2000s, this mislead a lot of people into thinking that Sauropods were puttering out even before the Asteroid hit the Earth.
|
|
#
?
Apr 15, 2024 02:18
|
|
|
McSpanky posted:Absolutely losing my mind at the cockatoo in every drawing, it's so cute And the Satin bower bird! It's so awesome to think of my backyard birds chilling with these guys. Megalania used to terrify me. There was a life sized model using the a bigger estimate at (what must have been? )the Australian Natural Museum in the late 80s/early 90s that gave me nightmares. I lived in the bush with big goannas everywhere (I could see a big goanna taking down a small child if it had a mind to) and it was way too easy for my child brain to imagine there still being Megalania sized ones still out there.
|
|
#
?
Apr 15, 2024 02:29
|
|
|
There's a youtube series by Linsday Nicole on the history of life on earth that is an excellent intro and primer into some of the cool extinct beasts. Nicole's bona fides are legit and she's fun to listen to. https://www.youtube.com/@LindsayNikole Here's the series, she's up to the Carboniferous so far. https://www.youtube.com/playlist?list=PLAXKicFIXWd9mguoAA5jsI9-jkgEaCH2k her catchphrase is "THAT we KNOW OF" and I like that, she emphasizes that when we state facts about the prehistoric world they're based on what evidence we've gathered so far, we're getting more, and our understanding will change over time. Really a big improvement over all those dinosaur books when I was a kid that just stated facts about dinos as if they were 100% certainties. Leperflesh fucked around with this message at 04:53 on Apr 15, 2024 |
|
#
?
Apr 15, 2024 04:37
|
|
|
I want to typeset khwarezm's post into a little booklet.
|
|
#
?
Apr 15, 2024 18:23
|
|
|
Darth Brooks posted:I want to typeset khwarezm's post into a little booklet. I already have and I'm putting it on Amazon
|
|
#
?
Apr 15, 2024 18:27
|
|
|
Smugworth posted:I already have and I'm putting it on Amazon https://www.youtube.com/watch?v=6RKpCbmemZQ
|
|
#
?
Apr 15, 2024 18:30
|
|
|
Has this thread covered drepanosaurs yet? Triassic reptiles with the heads of birds, bodies of chameleons, and big claws on their front feet and one on the tail? At least that's the typical body plan. Sometimes they did other things.  I want one of the big claw ones. I would give it a cat tree to climb on.
|
|
#
?
Apr 15, 2024 23:03
|
|
|
Knormal posted:Has this thread covered drepanosaurs yet? Triassic reptiles with the heads of birds, bodies of chameleons, and big claws on their front feet and one on the tail? These are adorable, and yes being them back so we can have them as pets.
|
|
#
?
Apr 15, 2024 23:11
|
|
|
Knormal posted:Has this thread covered drepanosaurs yet? Triassic reptiles with the heads of birds, bodies of chameleons, and big claws on their front feet and one on the tail? what the gently caress these are so cool
|
|
#
?
Apr 16, 2024 00:00
|
|
|
Thats one hosed up lizard
|
|
#
?
Apr 16, 2024 00:12
|
|
|
the one on the bottom almost looks like a katydid
|
|
#
?
Apr 16, 2024 00:19
|
|
|
Knormal posted:
So if these guys fall off the branch do they spin around on the way to the ground like sycamore seeds?
|
|
#
?
Apr 16, 2024 00:22
|
|
|
Snowglobe of Doom posted:They're just excitable, they're doing their best with the data they have available. I read that book a ton as a kid
|
|
#
?
Apr 16, 2024 00:32
|
|
|
Jimbone Tallshanks posted:So if these guys fall off the branch do they spin around on the way to the ground like sycamore seeds? If they don't then I'm glad they're extinct
|
|
#
?
Apr 16, 2024 00:34
|
|
|
Jimbone Tallshanks posted:So if these guys fall off the branch do they spin around on the way to the ground like sycamore seeds? Funnily enough there actually were a bunch of Triassic gliding reptiles with ridiculous looking setups for it, my favourite is Sharovipteryx that adapted its back legs into its main gliding surface, showing an impressive dedication to leg day:   Between this weirdos, the aforementioned Drepanosaurs and so many other things, I'm definitely doing a bunch of big posts on the clusterfuck that was the Triassic after I have my Late Miocene oceans one done.
|
|
#
?
Apr 16, 2024 00:34
|
|
|
tfw you finally unlock the Majora's Mask paraglider skin
|
|
#
?
Apr 16, 2024 03:31
|
|
|
Goatse James Bond posted:I read that book a ton as a kid Me too! I checked it from the library so often an entire checkout card was stamped just from me. Met Bakker once after a talk in the geology department, real cool guy. Feathered theropods were just starting to gain some traction in the community around that time, he really lit up when I asked him about it.
|
|
#
?
Apr 16, 2024 03:59
|
|
|
McSpanky posted:Me too! I checked it from the library so often an entire checkout card was stamped just from me. lol I am imagining the librarian who came to know your visits...
|
|
#
?
Apr 16, 2024 04:00
|
|
|
Looks like the thread's slowed down, but I'll do some more of these effortposts if people are still interested, this week's one is on the Late Miocene Oceans, with a particular focus on Western South America and the Pisco formation of Peru. So its, about 7 or 8 million years ago, South America and its gaggle of weird animals covered in this post has been moving steadily northward for millions of years by now, South America is still disconnected from the rest of the world, but already a chain of islands has sprung up in what's now central America that will soon create a continuous landbridge between North and South America, with massive ramifications for the world. As of this moment in time, a shallow sea exists where land does today, allowing easy exchange for animals between the Pacific and into the Caribbean and thus the Atlantic. This was extremely important for marine communities, as of now the disconnect between the Atlantic and Pacific created by the Panamanian isthmus forces marine life into isolation from each other, causing them to evolve in separate ways and considerably changing major aspects of the ocean's biogeography like currents, migration routes and the extent of shallow seas.   The Miocene (23 million to 5.3 million years ago) oceans were effected by other long term trends, as you can see from the map above, the northward progress of Africa has resulted in a similar situation as the Americas, with the once great Tethys Ocean getting crushed into oblivion by continental movement. The existing remnant in the form of the Mediterranean would actually dry up at a point in the Miocene when the strait of Gibraltar was closed off, creating a bizarre phenomenon called the Messinian Salinity Crisis, when the whole basin turned into a salty desert with dry land literally several kilometres below sea level with remaining pockets of water creating hyper-saline lakes like the dead sea, this lasted for a half million years before a major event called the Zanclean flood at the start of the Pliocene caused the straits of Gibraltar to be breached and the entire basin was refilled by cascading water from the Atlantic streaming into it, with a flow 1000 times larger than that of the Amazon river refilling the whole sea in a matter of a few years. Its almost impossible to imagine this actually happening but it really did, as far as I know its the biggest known flood in the history of the earth and considering that this was all done in a few years at max its amazing to think that such a massive change to the earth's geography would happen in such a short amount of time, could you imagine how unthinkable this would be from a human perspective? Just a massive 2,500,000 km2 sea just popping back into existence in a gigantic flood, PBS Eons has a cool video on this: https://www.youtube.com/watch?v=HooZ84rpovQ Meanwhile, going down to the very bottom of the earth, Antarctica has been growing an increasingly large permanent ice cap over the last few million years since the Oligocene, but in the Miocene this started to enter overdrive. Whatever land life had been clinging on in the increasingly frigid environment, be they Marsupials, Notoungulates and even Terror Birds, at this point faced their total annihilation as not even tundra environment could continue in the continent. The basic problem was that since it had become fully severed from both Australia and South America, with no land in the way a huge current enshrouded Antarctica, the Antarctic Circumpolar Current, probably the largest and most important current on Earth, it still exists and has been circling the landmass for almost 30 million years, defining the boundaries of the Southern ocean. The result of this is that warm water is forcibly kept away from Antarctica by the current, creating a runaway cooling effect that has had huge impacts on both the continent and the current state of the earth, combined with the continuous drop in world temperatures since the Eocene almost 50 million years ago this doomed Antarctica to its current state of being locked within into a gigantic ice sheet several kilometres thick that prevents anything bigger than a mite making a permanent living on land.   Now I'm not going to act like I really know what I'm talking about when it comes to paleoceanography, but to the best of my knowledge all of this stuff had huge ramifications on the Earth's oceans since it shut down tropical currents that could circumnavigate the entire planet when there were unimpeded by physical barriers that land presented from the Mid Mesozoic up to the Mid Cenozoic. Disrupted by continental barriers, currents in tropical areas became more localised, along with the marine life in these environments. Conversely, the largest and most powerful current on Earth was now an extremely cold one that dominated the Southern Hemisphere, combined with endlessly dropping temperatures this remade the ocean's environment to be colder and colder and more like what we see today. A period of sharp cooling is associated with a minor extinction event known as the Middle Miocene Disruption 14 million years ago, as ecosystems had to adapt to these long term trends. All the while, Marine ecosystems were forming into a position more and more like today. My understanding is that the aforementioned effects of cooling oceans and increasing isolation of oceanic ecosystems, along with continued effects of things like erosive land processes fertilizing the oceans, caused a dramatic increase in productivity in the seas in the latter half of the Miocene. Phytoplankton, particularly Diatoms, did well, this seems to be in large part because colder waters are typically more fertile, since there is greater mixing between different depths without the formation of strong thermoclines, which is further helped by current action and disruptive weather. On the back of these photosynthesizers, the cascading foodchain going from zooplankton all the way up to the largest apex predators benefits from increased productivity. Modern species of fish like Herrings, Sardines, Tuna and Marlins proliferated, along with swimming crustaceans like krill and copepods that fed animals like this. On the seafloor you had the familiar assemblages of molluscs and Demersal crustaceans and fish like crabs, flatfish and rays. Of note is that at the start of the Miocene, about 19 million years ago, sharks and rays (elasmobranchii chondrichthyes) seem to have suffered a very harsh extinction event that slashed their numbers by almost 90%, this was actually much worse for them than the losses they suffered during end Cretaceous extinction 66 million years ago, why this happened nobody even seems to have any theories on, especially since it doesn't line up with any other extinctions or major climatic shifts, but sharks still haven't recovered from it to this day. Regardless they would continue trucking and during the Miocene produced their most infamous member ever.    Sharks weren't the only long-running marine animals to take a mysterious hit during the Miocene, Nautiloids, represented today by the living Nautilus, went through a long and protracted decline. These animals have been around for almost half a billion years, all the way back to the late Cambrian period, withstanding every single mass extinction in Earth's history. After the extinction of the related Ammonites at the end of the Cretaceous, the similarly shelled Nautiloids moved into a lot of the vacant niches left behind as armoured, pelagic cephalopods that previously were so successful, but starting in the Oligocene and continuing to today their diversity cratered and they have been extirpated from most of the world with the exception of the waters around the Malay Archipelago and its extensive reefs, their final holdout. Why this happened was originally assumed to be because of some vague effects of climate change, but recent research has suggested a very strange alternate explanation, the decline of Nautiloids seems to correlate very, very closely with the spread of pinnipeds (seals and sea lions), the thinking goes that these marine mammals, who evolved in the Oligocene and spread throughout the world in the Miocene, happened upon an incredibly efficient and effective feeding strategy called 'pierce-feeding' that let them effortlessly bypass Nautiloids previously useful defences, making the shells worse than useless since they didn't work at all as armour and just slowed down the animal, letting pinnipeds just wipe them out wherever they found them. The Indo-Pacific area that living Nautiluses still live in is notable for having no native pinnipeds and seemingly never having them, everywhere else you find seals and such there's no Nautiluses, who knew that these animals could survive everything from gigantic volcanoes almost exterminating life on Earth during the Permian, to a massive asteroid wrecking the entire planet at the end of the Cretaceous, and everything else over the last 500 million years, just to find out that a bunch of dogs that learned to swim were the final boss that spelled their doom? One genus called Aturia seemed to be able to hold out for a while through the Miocene, they seem to have forgone heavy armour and evolved better evasive capability, but they went extinct about 5 million years ago. From then on, cephalopods have overwhelmingly been represented by their shell-less members like Squid and Octopus, where speed and smarts are the better strategies for the modern oceans.   One of the most impactful developments over the course of the Cenozoic oceans has been the emergence of two novel environments, both of which are odd, aquatic parallels to more familiar land based ecosystems. The first of these are seagrass meadows, built around seagrass, if you can believe it. These plants first started to appear during the Cretaceous, but I can't find much information about them before the Cenozoic when they really properly proliferated and created highly productive environments with animals specialised to live in them. Seagrasses are very strange, they are the only Angiosperms (flowering plants) that have adopted a completely marine lifestyle, I think they might even be the only plants from a completely terrestrial ancestor that's done that as well actually, they have special adaptations to live their lives completely submerged in salt water, and thrive in warm, shallow water around continental shelves down to a depth of roughly 50 meters. Like terrestrial grass they lock up a lot of carbon, help keep marine sediment in place, and provide food for a lot of animals. The other environment to mention here are Kelp Forests, unlike the seagrasses these are created by brown algae which, despite appearances, are in a totally different kingdom of life from plants, fully marine through their history. Kelp famously grows very long (up to 80 meters), and very fast(up to half a meter per day), preferring colder waters they tend to displace seagrass meadows and other such environments in more temperate or arctic latitudes, especially around the North West coast of North America or the South West coast in South America. Kelp forests are much newer than seagrass meadows, appearing mostly during the Miocene period, but both are massive concentrations of biodiversity in the oceans.   ]The emergence of these new environments allowed for strange new niches to pop up alongside them, a lot of animals have evolved to live within these areas, and it seems that the sheltered environments with a lot of refuge has been very important to the evolution of seahorses in particular, these most unusual fish descend from Pipefish and show up during the Miocene, abandoning most of the typical ways that fish evolved have developed to move in favour of this bizarre combination of a prehensile tail and flapping their tiny dorsal fins, methods that can only really work in seagrass beds and coral reefs and not the open ocean. They rely on their boxy skeletons and good camoflague for defense, mostly eating small crustaceans, their close relatives like Dragonfish have famously evolved particularly extreme camouflage to blend into their weedy homes. The earliest known seahorses like Hippocampus Sarmaticus come from deposits in Slovenia from about 13 million years ago.   A lot of living fish, crustaceans, echinoderms and even birds like parrot fish, sea urchins, bonnethead sharks, kelp crabs and kelp geese eat seagrass and kelp, but what's particularly noteworthy is that terrestrial animals that were herbivorous have been able to move into marine ecosystems and just start eating grass or kelp, these kinds of large secondarily aquatic tetrapods that have settled on a herbivorous lifestyle are, to my knowledge, extremely specific to the Cenozoic and particularly dominated by mammals at that. Most secondarily aquatic animals that move into the oceans are highly carnivorous, including all pinnipeds, cetaceans, penguins and sea snakes, this also extends even to extinct animals, Plesiosaurs, Mosasaurs, Ichthyosaurs, Nothosaurs, Thalattosuchians and Placodonts are, to the best of my knowledge, almost overwhelmingly understood to have eaten animals of various sizes, not plants or algae. The only exception I can think of is a strange Placodont called Atopodentatus, but we'll cover that at some point in the future. Additionally some sea turtles like the Green Sea Turtle have evolved to eat sea grass as they get older. Back to the Cenozoic, I can think of at least three lineages of marine mammals that became specialised aquatic herbivores to exploit these new environments. The first are the ones that are still alive today, Sirenians, manatees and dugongs, without going into too much detail they evolved around the Eocene, 50 million years ago from elephant or hyrax like ancestors, and today are extremely specialized into a diet overwhelmingly consisting of seagrass, with the recently extinct Steller's Sea Cow being a huge animal that was specialized in eating the Kelp that grows in the North Pacific, their small population was wiped out by Russians soon after they discovered them in the 18th century near the Commander islands.   Next you have the Desmostylians, these weird animals are considered the only extinct order of marine mammals, they seem to have evolved during the Oligocene and died out at the end of the Miocene, and its unclear what they are closely related to, with theories suggesting either Sirenians or Perissodactyls as their closest relatives. Desmostylians were restricted to the northern Pacific, eating sea grass and kelp they seem to have been adapted to walk along the ground underwater, with big heavy bodies and thick bones keeping them submerged like a hippo. Larger species like Paleoparadoxia or Desmostylus might have reached up to 3 tonnes, but they went extinct probably due to competition from Sirenians and changing climate and habitats (ironic because no Sirenians currently exist in their old haunts despite the rich kelp forests of the North Pacific). They were around up to about 7 million years ago, just in time to perhaps encounter some very scary predators if they wandered outside their usual habitats a bit into more open waters from places like northern California or Japan. As you can see from the skull below they had very weird looking forward pointing tusk like teeth, in addition they also had very tightly packed molars that almost looked like hexagons for grinding up their food.     Finally we have probably the most unexpected of the lot, Thalassocnus a genus of ground sloth (or sea sloth in this case?) that showed up in the late Miocene (just as Desmostylians went extinct, natch) and seems to have adopted a very similar lifestyle of living as a marine herbivore eating sea grass down the west coast of South America, managing to do so without many swimming adaptations but seemingly walking along the sea floor like their northern counterparts. A testament to how absurdly adaptive and resilient sloths can be, they might have been pushed towards this lifestyle as terrestrial plants became harder to find with aridification of the western coast, not much to eat in the Atacama desert, it got up to three meters long and had similarly heavy bones to keep it underneath the water, getting more specialized for this lifestyle as time went on, with them having to learn how not to get eaten by the various hungry predators swimming around. Apparently these poor animals also have signs of very heavy injuries from being tossed around by waves during bad weather when they were close to shore.   These sorts of environments were intrinsically shallow water and might have served as useful refuges for various larger animals who otherwise lived more in the open ocean, especially for the purposes of breeding. Its easy to imagine cetaceans and perhaps also sharks coming here to give birth since the young would be more protected here. But shallow demersal environments had other opportunities, notably a lot of molluscs that would make beds of things like clams and oysters on the sea floor, in addition to all of the other benthic crustaceans, fish and worms that live on the sea floor. In South America a very odd kind of whale evolved to exploit this niche, Odobenocetops, looking like some kind of unholy fusion of a Narwhal and a Walrus. Like both animals it had extremely elongated tusk like teeth (its only teeth actually), its habits seem like they would have been similar to walruses based on its jaw shape, rooting through the sediment on the sea floor and sucking up any shelled animal it found. The tusks show clear signs of sexual dimorphism, the right tusk is hugely more elongated in certain individuals, probably males, just like Narwhal tusks, and have signs of wear. What they were using them for is very hard to determine, we don't even really know the function of Narwhal tusks and they're alive! Most theories are either that it helped in some way in rooting through ocean sediment or had a function in sexual display or combat over mating rights. The difference between males and females strongly supports the sex selection idea, but its unclear what exactly, they seem too fragile to be used in combat but then a lot of the specimens have damage associated. Females still had short tusks, and male tusks only elongated on one side, implying they might have had a more pragmatic sensory or feeding function we still haven't been able to pin down in addition to a sexual role. The animal also had a very large range of motion in its neck compared to other whales and might have even had sensory hairs on its face to help it find food, again like a Walrus, and it was about the same size as a Walrus, up to a tonne and about 3-4 meters long.   Since we've brought them up now I'm going to dedicate a massive chunk of this post to other Cetaceans, which reached their greatest diversity during the Miocene and are the most important fossils of the Pisco formation. I won't go into detail about their evolution in this post, but suffice to say, about 50 million years ago a wolf like hooved mammal in modern day Pakistan started going for a swim in the sea and tens of millions of years later their descendants evolved into dolphins and whales. The earliest whales that were completely disconnected from the land were the weirdly elongated Basilosaurids of the late Eocene, who quickly got really big, we might cover them in a future post but after a few extinctions and adaptations to the changing oceans by the Miocene, the modern groups of Cetaceans had arrived that are still alive today, Mysticeti and Odontocetes. Mysticeti are baleen whales, they've evolved to lose their regular teeth and replaced them with hair like baleen to allow them to efficiently filter feed, taking huge gulps of water to consume vast clouds of small fish or crustaceans like krill, straining out the water and leaving behind the food. In the Pisco formation there are a number of well preserved species that lived in the waters, including Piscobalaena and Incakujira, these animals are considerably smaller than the average living baleen whales toay by and large, around 4-6 meters long and a few tons, comparable to things like Minke Whales or Pygmy Right Whales.   Odontocetes are toothed whales, a slightly misleading term since some of their living members have mostly lost their teeth. Still, most of them have at least a few, they include living dolphins, beaked whales and sperm whales, in addition to teeth their most notable characteristic are their unique ability to echolocate, and their extremely keen intelligence. Echolocation in particular is something of a super-power for these animals, I can't think of any other marine animals that can do it but its incredibly useful to help locate food and find their way in dark and murky waters over long distance, and their whole face has been configured to accommodate it, its why dolphins and such have that large melon structure in the front of their face to help direct and pick up their sonic rays. Living sperm whales produce the loudest sounds on earth and some people think they might be able to use their sonic blasts as a weapon, these animals have very complex social structures and verbal communication, even among whales, with very large brains to boot. Odobenocetops was a tooted whale, and most species living and dead were high level predators that were built to hunt fish and larger prey. The fact that they are warm blooded seems to give them an advantage against ectothermic fish and squid, which might have helped prompt higher metabolism levels and more efficient body plans in fast pelagic fish like tuna or marlin, who are almost warm blooded themselves. Tooted whales have shifted a lot in their habits, to focus in on beaked whales, these are part of the family Ziphiidae and notable today for being some of the most elusive animals on earth, we know they are quite diverse, with more than 20 species, and can get as large as 12 meters, but they are very, very rarely seen and almost impossible to study because they seem to have specialised for spending most of their time very deep underwater in the open ocean looking for deep sea fish and squid, mostly alone in dives that can last hours. Some species are only known from a few sightings or even just a few washed up corpses, no other large mammal is this poorly known, we aren't even sure if we've found all of the living species. Back in the Miocene they seem to have been less specialised for this sort of lifestyle and species like Messapicetus looked and lived more like dolphins, particular specimens from Peru have been found that seem to have been eating sardines in shallow water that they vomited back up before puttering out (possibly poisoned by algae), the environment and type of food is very different from modern beaked whales. These animals also had tusk like teeth in its lower jaw that might have been used for fighting each other, this is commonly seen in modern beaked whales. These dolphin like whales were probably displaced by actual dolphins over the Pliocene up till today, hence why modern beaked whales are specialised for deep diving.   Another dolphin-like group of cetaceans were the Eurhinodelphinids, who were a few meters long and evolved this bizarrely projected, thin and slightly curved upper jaw that seems to have had almost exactly the same function as the sword of a modern swordfish or marlin, letting that slash at small fish at speed before gobbling them up.    The other dolphins that were knocking around the Pisco formation aren't even closely related to familiar modern dolphins like bottlenose dolphins, instead species like Isthminia and Brachydelphis seem to be more closely related to living Amazon River Dolphins and the La Plata Dolphin, which are quite different from animals in the modern family Delphinidae. These earlier dolphins probably got displaced by modern dolphins and mostly continue to exist in freshwater refugia environments. Of course these dolphins still had river bound members, and something I didn't mention in my previous South America post that I may as well here is that there was a giant species of river dolphin in Peru during the Miocene called Pebanista that was about 3.5 meters long, compared to a modern Boto at roughly 2.3 meters. Weirdly it was more closely related to living Ganges and Indus river dolphins than Amazon dolphins.    Beaked whales and dolphins are cool enough, but the big heavyweights of the Miocene seas were from a totally different group, the sperm whales, or Physeteroids. The living sperm whale is the largest predator of large animals on earth, with lengths that can exceed 18 metres and weighing more than 50 tonnes in large males, but they are specialized into deep water diving and sucking up big cephalopods like giant squids. Already these are intimidating animals, but their extinct relatives were something else entirely. A term that's used to describe these Miocene sperm whales is 'Macroraptorial', instead of focusing on soft bodied cephalopods these whales seem to have been specialized into hunting down other whales, any other large sea creatures they could find. Modern Sperm whales only have thin teeth on their bottom jaw, mostly to just stop squid from escaping, Macroraptorial whales had massive cutting teeth on both jaws and seem to have used them to rip and tear at the small baleen whales, pinnipeds, fish and penguins they shared their environments with. One of the smaller such whales was Acrophyseter, about 4.5 metres long, comparable to a big dolphin, it still sported nasty looking teeth and probably could have easily killed penguins and seals.   The next step up from this was Zygophyseter, this animal would have been about 7 metres long, comparable to a modern Orca, and probably capable of attacking animals in a similar size range as orcas can, up to and including the aquatic sea sloths, small baleen whales and pinnipeds.   Neither of these fellas could compete with the real king though, Livyatan Melvillei, a completely ridiculous animal that seems to be in the running as the largest and most dangerous predator in Earth's history. This was a huge whale where size estimates range from 13 to 17 metres in length, with a potential weight in excess of 50 tonnes. There's a lot of debate about how to properly scale these animals, some scientists suggest that the skull its mostly known for might have been disproportionality large compared to other whales, going for shorter lengths, others scale it to both the living sperm whale and extinct macro-raptorial relatives to get larger lengths, with scaling off its closest relatives giving the largest estimates. Either way, just going by its skull alone it was a titan, the holotype skull is more than three meters long and it seems to have had probably the largest bite of any tetrapod in history, along with also having the largest non-tusk teeth. Its teeth alone are just ridiculous, each jaw was packed with gnashers that at the smallest were 30 centimetres long, comfortably outsizing the biggest Tyrannosaurus teeth. Although its skull was found in Peru, its teeth have been recovered from around the world and it probably lasted into the Pliocene epoch. This animal outclassed almost every other major marine predator in history, including every Mosasaur, Pliosaur, and other whales like Basilosaurus, the only other big predators that came close were some Triassic Ichthyosaurs like Shastasaurus and a contemporary pal of Livy we'll get to in a moment. Eat your heart out Jurassic World!    Like modern sperm whales Livyatan and its relatives seems to have had a very well developed spermaceti organ that could facilitate its sonar capabilities (and maybe used for offense like some kind of videogame boss). Living Sperm Whales have extremely complex social systems and recent research into their communication and intelligence seems to suggest that they might have a straight up, actual language, able to communicate with each other over huge distances to interact in complex ways like passing on information for good feeding locations. I don't know if Livyatan could do this, but its amazing to think how terrifying it must be for a little baleen whale just trying to eat some krill when a fifty tonne monster with banana sized teeth and a sonic boom attack might literally have been telling its friends where the eating's good while they use their impressive brain power to formulate a plan of attack. Livyatan could eat almost everything that existed alongside it in the Miocene oceans, but not quite everything...   Amazingly, Livyatan wasn't actually uncontested as being the king of the seas of the Miocene, much to the chagrin of those other little whales. Now we come to one of the most famous extinct animals of them all, the giant shark Megalodon. This shark is just stupendous, the estimates range up to 20 metres in length, with a possibility that it could get even bigger, and some weight estimates based on this scale cause it to exceed 100 tons, in other words, the size of some adult blue whales today. More constrained, and likely, estimates bring it down to more like 17 metres and 60 tonnes, having said that a recent study has supported the idea that it was more elongated than previously assumed, probably regularly reaching 20 meters but with less bulk than the previous estimate to that length. I feel like recent studies have been pushing the size of this animal higher and higher, its hard to get a handle on what exactly might be the true dimensions, but its plausible that nothing approached it at the biggest sizes. A lot of the issues with reconstruction come from the fact that shark remains are mostly restricted to teeth, Megalodon's teeth are, predictably, ginormous. More than 7 inches long, they are almost four times the size of a Great White Shark's teeth and accordingly a lot of the size estimates are based on scaling up from Great Whites. There actually is other material, while cartilage from sharks is bad at preserving, it does happen from time to time, we have some vertebral columns from Megalodon that help with reconstruction. Previously Megalodon was assumed to be within the Carcharodon genus, like Great Whites, and it was assumed it was literally just a massive Great White in appearance (you see this in most reconstructions, especially in TV and movies), but recently its been moved to its own genus called Otodus and it seems its similarities with Great Whites is mostly just convergent evolution, another big Miocene shark in this Genus is Otodus chubutensis, that was probably twice the size of the biggest Great Whites and lived earlier in the Miocene compared to its big brother, its shown in the family portrait below as its second largest member.   Megalodon teeth are extremely common and show that it had a worldwide distribution for almost 20 million years, it probably had a huge effect on the structure of marine ecosystems, especially in conjunction with Livyatan. The fact that these titanic sharks and giant whales could live at the same time, seemingly in a similar position on the top of the food chain, is probably an indication of how incredibly productive that the Miocene ocean was. We have direct evidence of Megalodon preying on the largest baleen whales in its environment and they could probably eat anything, in fact at least one study has shown that baleen whales of this period grew much faster and lived much shorter lives than contemporary whales, most likely an indication of how impactful these predators were on ocean ecology. As mentioned sharks at the start of the Miocene had gone through a very heavy extinction event that almost killed them off, but they became more adapted to open water hunting and existing in the increasingly cold waters of the Miocene, sharks up to the present day have evolved a very efficient metabolism and internal heating system, its not quite warm bloodedness but it allows them to operate as pursuit hunters in a wide variety of water temperatures that help keep them viable in colder waters. Having said that, there Megalodon was probably not able to cope with the cold waters of the polar regions and was probably excluded from these productive areas, which were more monopolized by warm blooded cetaceans and pinnipeds. There's also controversy on how they should be reconstructed, since its become more apparent that its not close to Great Whites some people have suggested a much more unusual look, making it more of a bulldog shape as can be seen below with a rotund body and mouth much closer to the tip of the snout, I think this is considered an unlikely reconstruction though. Its been suggested that it might have employed something of a ramming strategy to kill prey, trying to disable them by doing massive damage to fins and tails before moving on to the body cavity to try and target the heart and lungs. Megalodon might have been the single largest and most dangerous predator in all of earth's history, with Livy as a close runner up.   In these discussions its always super tempting to think who'd win in a fight between Megalodon and Livyatan, while meg was probably bigger, Livyatan was probably far more intelligent and could probably call in back up with its likely much more complex social system. The boring but probably truthful answer is that both predators would likely avoid each other as much as possible because attacking the other was probably a guarantee of significant injury at the very least and modern sharks are actually very careful predators that go to extreme lengths to avoid the risk of injury. Still, have a few pictures of wacky encounters for your inner ten year old:   All of these giant predators, we need a bit of a palate cleanser. I think now is as good a time as any to talk about the last major group of marine mammals, which we've already touched on as part of the Nautiloid extermination service, Pinnipeds. Unlike Cetaceans, Pinnipeds are younger, they seem to have entered water around the Oligocene and still have land adaptations since they return there to breed. They are Carnivorans, mostly closely related to things like stoats, unlike whales that are Artiodactyls (even toed ungulates) most closely related to hippos. Pinnipeds have three living groups, eared seals, otariids (ie sea lions), earless seals, phocids (ie harbour seals) and Walruses. The Miocene was a major time of Pinniped diversification and there seemed to be more groups of things like Walrus line pinnipeds. In the Pisco formation we have fossils of the seal Acrophoca an earless seal with an unusually long neck that seems to have been related to living Leopard seals, and like it could probably do some filter feeding with its odd teeth, and Hadrokirus, also earless that seems to have tough jaws for going after shellfish.   Further north, along the coast of North America there seems to have been a number of Walruses that stayed true to the family tradition of having very odd tooth morphology, Gomphotaria from California had these four, forward facing tusks it might have used for combat or digging through sediment, it looked more like a Horker from Skyrim than a real Walrus, and probably was a fair bit bigger than living Walrus.   Alongside Gomphotaria you had a huge animal named Pontolis, this seems to have approached the dimensions of a big Southern Elephant seal today, up to 4 tonnes, one of the largest pinnipeds ever, with less pronounced tusks than its relatives it lived more like Sea Lions and Elephant seals too.   Finally, there was also an extinct family of Pinnipeds from the North Pacific, the Desmatophocids. They seem more primitive than the other groups, being more land orientated like Sea Lions, they seem more adapted for eating at greater depths and might have had sensitive vision for this, but went extinct at the end of the Miocene with 3 meter long Allodesmus being their last member.  Having covered the mammals and fish, we'll go through the last few major groups in the Miocene oceans I want to touch on, the first of course are birds, in the Pisco formation we have extensive fossil records of a variety of Penguins, including those that are very closely related to the living Humboldt Penguin from along the west coast of South America. These are Banded Penguins from the genus Spheniscus, penguins as a whole deserve quite a lot of respect they aren't normally given, I can't really go into detail here but they are far more ancient than people tend to realize, they first appear very soon after the K-Pg mass extinction about 62 million years ago, around the southern hemisphere with early fossils being found in New Zealand, Waimanu, below left. They are actually the second oldest still living marine Tetrapods, the only animals older are Sea Turtles, so penguins have been swimming longer than the likes of whales, seals and manatees. Ancient penguins could get very big, up to 1.8 meters tall with Anthropornis (below right) from Eocene Antarctica, but competition from newly arriving marine mammals probably pushed them out of their large bodied roles into the smaller animals they are today.    Regardless, they were plenty successful during the Miocene, as mentioned they are common fossils in the Pisco formation of the Genus Spheniscus, with Spheniscus megaramphus being a big long beaked species, alongside the familiar Humboldt Penguin.   Penguins fly through the water, but flying through the air the air was something much more dramatic. In addition to the other recognizable sea birds like albatrosses, gulls and boobies, there also existed a very unusual soaring bird called Pelagornis, this seems to have had similar features to modern Albatrosses, but was doing it on a far grander scale. The estimated wingspan for Pelagornis is an astonishing 6.5 meters, twice the length of the modern Wandering Albatross (which has the longest wingspan on any extant bird). It had the longest wingspan of any bird ever, although Argentavis Magnificens (covered in my South America post) was probably significantly heavier. Like existing albatrosses it probably made use of ocean winds to keep aloft for weeks or months on end, it might have weighed up to 40 kilograms and actually was comparable to some big Pterosaurs like Pteranodon, which it outclassed in terms of wingspan.   The weirdness doesn't stop there, despite the superficial resemblance to Albatrosses, its actually unclear what Pelagornis is closely related to. Its part of a group of birds called Bony Tooted Birds, and, as you can see in the pictures enclosed, its a very descriptive name, birds don't have teeth anymore but clearly there was a strong incentive for something with Pelagornis's lifestyle to have them or rather a close facsimile, probably to help in catching fish. And accordingly they just evolved bony projections coming straight out of the jaw to fulfil this function, they aren't true teeth, and are considered 'Pseudoteeth', but did the job well enough. Pelagornids just barely missed out in interacting with humans, going extinct just a couple of million years after about 20 million years alive, and their remains have been found all over the world but especially in Peru.   The very last animal worth mentioning is, of course, a marine crocodile. Its been quite common for crocs to try out fully marine lifestyles with ancient groups such as Thalattosuchians and Dyrosaurs from the Mesozoic, and the abundance of food during the Miocene prompted several species of Gavialid crocodiles (like the modern Gharial) that were more specialized fish eaters to become marine. These show up again in the Pisco formation and the largest species was an 8 meter long fella named Piscogavialis, who snapped up fish with its long thin jaws alongside the sloths, whales and penguins.   Sadly, insofar that I can be sad that giant sea monsters aren't still roaming the waves, it wasn't to last. The processes that helped make the Miocene so productive also worked to change the world further and bring an end to the conditions that let things as varied as Megalodon and Thalassocnus survive. The oceans continued to cool, going into the Pliocene this disrupted habitats as productivity started to shift towards the poles, this made things harder for ectothermic animals like Crocodilians and Sharks that couldn't so easily deal with cold waters. Baleen whales in particular started to move further away from the tropics and get bigger, making it harder for them to be preyed on by the giant carnivores. Alongside this, the final closure of the connection between the Caribbean and Pacific with the formation of the Panama isthmus seems to have wrecked havoc with marine ecosystems in what was probably the most productive place on Earth, this happened in conjunction with a general drop in sea levels and especially along the American coastlines this removed a large amount of shallow seas that animals had become dependent on. This was probably particularly devastating to Megalodon, which may have needed these waters as spawning grounds, and there seems to have been a collapse in the sea grass meadows in South America which probably killed off the marine sloths. Cetaceans suffered a general drop in diversity which likely stressed the big predators, and Orcas started to emerge as a major predator in their own right that probably helped displace Macroraptorial sperm whales and giant sharks. A sharp series of extinctions during the Pliocene about 5 to 3 million years ago spelled the end for the older dominant animals, and the modern state of the oceans emerged in its wake. Megalodon and Livyatan were a thing of the past, it was at this point that Baleen whales, probably freed from intense predatory pressure and fed by the ridiculous abundance of food in the polar regions, absolutely explode in size. The giant animals we are familiar with today are very recent in evolutionary terms, only emerging in the last couple of million years. Meanwhile modern dolphins take over a lot of major roles we see today including the most important top level marine predators in the forms of Orca. So it goes, I suppose we'll just have to see how these animals can deal with humans and global warming. Western South America actually remains a very productive marine environment today, but its makeup is probably quite a lot different from what it used to be and its mostly because of the cold water Humboldt current bringing nutrient rich water up to tropical regions, creating a glut of food for modern whales, fish, seals and seabirds.   Anyway I hope everyone enjoyed that, apologies that these posts just get longer and longer but there's so drat much to talk about. I hope all the images don't cause your computer to catch fire. I might have to do a separate post trying to attribute the artists but if I don't then I should mention, again, that the likes of Gabriel Ugento, Nyx Illustration, Hodari Nundu, Atolm and others I can't pull the names up for are really good for these images. If anyone has any comments, especially on the various things I almost certainly got wrong (I feel like my understanding of Miocene oceanography and climate probably has a lot of holes), please don't hesitate to say something and offer corrections. the next series of posts I may do will probably be stuff focusing on the Triassic period, since we're on the topic of giant sea creatures, I may give a little preview!  11-Year-Old Uncovers Fossils of Giant Ichthyosaur in England, the Largest Marine Reptile Ever Found, Scientists Say Stay tuned! khwarezm fucked around with this message at 01:44 on Apr 22, 2024 |
|
#
?
Apr 22, 2024 00:14
|
|
|
Well, I read all of that post and had not heard of a single one of those animals before so that was super educational and very cool. Thanks khwarezm for going to all that effort! I love the enormous, human-sized penguins.
|
|
#
?
Apr 22, 2024 01:19
|
|
|
the giant gently caress off sharks and giant gently caress off whales do not gel well with my slight thalassophobia so i am glad that they are dead i do want to tackle a giant pengiun though
|
|
#
?
Apr 22, 2024 07:18
|
|
|
Great posts. I wish I had something substantial to add besides my appreciation.
|
|
#
?
Apr 22, 2024 09:15
|
|
|
Non Compos Mentis posted:i do want to tackle a giant pengiun though Have you ever seen the inside of a penguin's mouth?  Now imagine that but in a 6' tall creature, that's nightmare fuel.
|
|
#
?
Apr 22, 2024 09:15
|
|
|
khwarezm posted:Anyway I hope everyone enjoyed that, apologies that these posts just get longer and longer but there's so drat much to talk about. Don't ever apologize for these posts, they're great. I never knew how big divers used to be. Incredible!
|
|
#
?
Apr 22, 2024 09:34
|
|
|
Amazing thread, love the long posts! If anyone wants to take a piece of our extinct forebears home with them, you should check out Bone Clones. Amazing osteological reproductions, for decent prices too. Lots of stuff there that won't break the bank. I've got a Smilodon skull from them, as well as Megalodon tooth. Lots of amazing reproductions, life casts, study pieces, and just general cool stuff. Perfect for those that want some fossil bones, but can't afford the real thing, or the dubious ethics involved with obtaining the real thing in many cases.
|
|
#
?
Apr 22, 2024 09:56
|
|
|
Snowglobe of Doom posted:Have you ever seen the inside of a penguin's mouth? i can take it in a fight
|
|
#
?
Apr 22, 2024 10:02
|
|
|
Kurash posted:Great posts. I wish I had something substantial to add besides my appreciation. Not an emptyquote. This thread is amazing
|
|
#
?
Apr 22, 2024 10:06
|
|
|
i was looking at their primate skulls and i never realised how close a baby gorilla skull is to a human babies  like that could just be the skull of a human baby with a defect
|
|
#
?
Apr 22, 2024 10:08
|
|
|
khwarezm posted:(incredible post) Thanks again, these posts are the best. You've got me drawing extinct critters again! Non Compos Mentis posted:the giant gently caress off sharks and giant gently caress off whales do not gel well with my slight thalassophobia so i am glad that they are dead Oh for sure, I can't look at that turbo-toothed whale without my palms sweating. e: drew this for the excellent pyf comics thread, but it works for this one too 
Tree Bucket fucked around with this message at 11:43 on Apr 22, 2024 |
|
#
?
Apr 22, 2024 11:25
|
|
|
I bet all the other animals bullied the poo poo out of sea-sloths
|
|
#
?
Apr 22, 2024 12:14
|
|
|
I absolutely love your effortposts, please keep making them! It's rare to find text-based lay information for adults on paleontological topics, especially for non-Mesozoic (and realistically, non-Cretaceous) fauna. I hadn't heard that about nautiloids before. Do you know why it might be that pinnipeds never made it to Malaysian waters?
|
|
#
?
Apr 22, 2024 12:20
|
|
|
Tree Bucket posted:Thanks again, these posts are the best. You've got me drawing extinct critters again! Lmao this is so good Also amazing work on the in depth posts op!!
|
|
#
?
Apr 22, 2024 13:10
|
|
|
Tree Bucket posted:Thanks again, these posts are the best. You've got me drawing extinct critters again! You better post these new drawings! On a side note, I love the old trope that for some reason, whenever a dinosaur is being shown in its environment there has to be a volcano going off in the background. How did this idea even start? Its very random. I at least get why people are endlessly drawing an asteroid about bonk a T-Rex on the head, but the volcano thing is quite puzzling to me since they had to deal with them about as much as we do, and as disappointing as it may be, usually when I go outside there's no visibly exploding volcanoes in sight. Peanut Butter posted:I absolutely love your effortposts, please keep making them! It's rare to find text-based lay information for adults on paleontological topics, especially for non-Mesozoic (and realistically, non-Cretaceous) fauna. Thanks, that's actually a really good question, I'm not expert but as far as I understand, tropical waters seem to be a very difficult to cross barrier for a lot of sea life, but especially for swimming birds and mammals. If you look at the map below you can see that seal diversity is super concentrated in the polar regions and trails off as you head to warmer waters, with them being essentially non-existent in the equator. The reasoning I've heard for this is that warm blooded animals like seals have huge advantages when it comes to pursuing their cold blooded prey like fish and squid in cold waters, and just generally since colder waters are more productive there's a big glut of food for them to exploit. As you get to the equator, these advantages trail off, and Pinnipeds can't operate as effectively, especially in the cramped, constrained environments like Coral reefs that most tropical sea life concentrates into.  Penguins actually seem to have a similar issue, their range is restricted to the southern ocean and the southern fringes of Africa, Australia, New Zealand and South America where the water is coldest, and they have their highest diversity close to Antarctica. Both Pinnipeds and Penguins have a bit of a sweet spot in the Galapagos where the cold ocean currents bring favourable conditions almost to the equator.  There are three species of seals that are kind of specialised into warmer water, these are the Monk seals. They live in the Mediterrenean, Hawaii, and used to live in the Caribbean but unfortuntely that species was exterminated (like the Thylacine we have a photo of a living animal below), they are famously shy and generally seem to have always been rarer compared to other seals, which probably indicates the tropics just aren't great seal habitat. Monk seals never found their way over to the great Indo-Pacific shallow seas around South-East Asia and Oceania, its probably just too far for them to travel from Hawaii.   Cetaceans are more adapted to open pelagic lifestyles and their size lets them cross these climate barriers if they need to, but they still have higher diversity in colder waters and the polar regions are absolutely crucial for the massive Baleen whales to get enough food to live. I know that Humpback whales and some other big species will go and give birth in warm waters during winter because its easier for the calf (and there's less predators around), but to do this the mother essentially has to fatten up hard beforehand because she'll be in some tropical place in the Caribbean or Hawaii feeding her calf for months before heading back north and finally getting a proper meal.  The divergence between north and south created by these climate barriers are so intense that some groups like Penguins, famously, have never been able to cross them. I'm sure if they could that Penguins could thrive in Greenland or Alaska but they can't get past the equator in their entire 60+ million year history, this is actually why you have Auks like Puffins and Guillemots that occupy an almost identical niche to penguins but are totally different birds, albeit they can still fly which helps with migration, finding nesting sites and escaping land predators, but also compromises their ability to swim and restricts their size. Auks also can't cross the tropical barrier and are stuck in the Northern hemisphere. The extinct Great Auk actually used to be a big flightless swimming seabird, its actually where the original word penguin comes from, clearly converging on the same lifestyle as living penguins, but they were hunted to extinction in the 19th century.  
khwarezm fucked around with this message at 13:59 on Apr 22, 2024 |
|
#
?
Apr 22, 2024 13:56
|
|
|
khwarezm posted:You better post these new drawings! Great Auks are probably one of the only extinct species of which we likely have a personal account of the final act of extirpation https://www.smithsonianmag.com/smithsonian-institution/with-crush-fisherman-boot-the-last-great-auks-died-180951982/
|
|
#
?
Apr 22, 2024 14:07
|
|
|
free hubcaps posted:Great Auks are probably one of the only extinct species of which we likely have a personal account of the final act of extirpation I'm not reading that link because it will make me sad and/or angry. Anywho, here's a colourisation experiment from the now-extinct (haha) dimetrodon thread. 
|
|
#
?
Apr 23, 2024 09:13
|
|
|
|
| # ? May 6, 2024 12:22 |
|
|
its a shame we dont know what colour an extinct animal was
|
|
#
?
Apr 23, 2024 10:36
|
|