|
So, why did it rain for two million years? e: I'm also baffled by the Nautiloids being unsinkable until dogs learned to swim. How big did they get? I've been looking at this picture and thinking the thing is killer whale sized: 
Nebakenezzer fucked around with this message at 18:58 on May 13, 2024 |
#
?
May 13, 2024 18:53
|
|
|
|
| # ? May 29, 2024 23:42 |
|
|
Nebakenezzer posted:
I think the biggest one we know of is a Cretaceous fossil found in Germany that's a bit over 6 feet across?
|
|
#
?
May 13, 2024 19:09
|
|
|
Darth Brooks posted:I want to write a story where aliens come to Earth to check on the probes that they left. When people ask "What probes?" as a small flock of butterflies show up. The aliens explain that butterflies are a designed species left on Earth as a benevolent and incognito sensor. If the butterflies are killed off it's a sign that something went wrong. Then someone asks if moths were left too and the aliens respond "You have moths?" They look at each other nervously and then quickly leave. if humans ever leave earth we’ll be bringing rats, mice, cockroaches, fire ants and mosquitoes with us like it or no aliens will think we intended them as bio weapons and we’ll have to explain that no we are just dirty sorry fellas
|
|
#
?
May 13, 2024 19:16
|
|
|
  Previously on the Triassic, land Pseudosuchians dominated the earth, Synapsids have been increasingly shunted aside, Rhynchosaurs rose quickly and fell quicker, a bunch of silly animals made a mockery of the concept of surivival of the fittest, and Dinosaurs have appeared, like the long lost brother dramatically slamming open the doors of the foyer to claim his inheritance in the season finale. In this post I'm going to do my best to try and cram in the endgame for terrestrial life in the Triassic, this will be the end of the Norian period and the entirety of the Rhaetian period, the last roughly 20 million years until the terminus of the Triassic and the beginning of the Jurassic 201 million years, with the overall Triassic period itself having last just over 50 million years. I'm going to format this post differently and pick up where we left off previously, because the earth goes through dramatic and traumatic changes at end of this period I think that might be best left until the end, and we'll revisit the other major animal groups as well to see how things stand with them in this endgame period. Dinosaurs, ya love 'em, ya know 'em, ya might even be eating 'em. The most iconic of iconic extinct animals, we've covered their earliest evolutionary relationships last week, and we can finally cover the first actual, proper dinosaurs now. As mentioned, Triassic dinosaurs come from a divisions of Archosaurs called Ornithodirans, traditionally (I'm going to just ignore the Ornithoscelida hypothesis and all of that nonsense involving Silesaurs since we covered that last week) they have two main divisions, Ornithischians and Saurischians. Saurischians are the only Dinosaurs that have definitive, incontrovertible evidence of their existence during the Triassic, and usually you see them divided into two familiar groups, the Sauropods (big herbivorous dinosaurs with long necks and tails, famous members include Diplodocus and Argentinosaurus, these animals are comfortably the largest land animals in Earth's history) and the Theropods (the overwhelming majority of predatory dinosaurs include the largest land predators in Earth history, like Tyrannosaurus, but also a wide variety of body sizes and lifestyles, including living birds), but this division (surprise, surprise) is much less clear cut when dinosaurs first appeared in the Triassic and most of these early dinosaurs have been classified as being more basal than we used to think, predating the split into Sauropods and Theropods and representing animals that have confusing affinities that can be difficult to pin down. Broadly, earliest Dinosaurs look and act like your stereotypical Theropod, bipedal, energetic, carnivorous etc, and that tended to result in them being assigned to Theropods before their relationships and morphology were given more scrutiny, since which there has been a greater tendency to reorganize their phylogeny outside of the Theropod/Sauropod binary. The absolute earliest animals that can be called dinosaurs is a subject of considerable debate, not helped by the sketchy remains we have to work with, a frequently cited candidate is Nyasasaurus from Tanzania, even the age of this animal hasn't really been pinned down, it was probably from the Carnian despite earlier claims that it was much older, though if they were true it would mean it was more than 240 million years old. I'm not going to dwell on this much because the general consensus I've seen on this animal is that there's gently caress all material to go off, Triassic animals are always a pain to categorize, its probably not even a dinosaur, the best that can be done is to hope for more bones to be found. Even when trying to categorize this animal as a dinosaur, its so poorly known that its been placed in all three major dinosaur groups by different authors, as well as (of course) the Silesaurs.  To talk about solidly, uh dinosaur dinosaurs, we return to Carnian Argentina and find Herrerasaurus as we ended the last post with. This is an exceptionally important dinosaur and one of the first that seems to have made a big impact on its ecosystem, it was a medium sized predator that averaged out at about 3 meters long, but some members of the family might have reached up to 6 metres long, and might have approached 350 kilograms, which is comparable to something like the much later Utahraptor, albeit we are talking about scanty remains for these larger specimens. Herrerasaurs as a group are the main example of those dinosaurs previously thought of as theropods but later reclassified into their own thing, they are likely to have split from ancestral dinosaurs before the big Theropod/Sauropod split, which shows that the features we tend to use to determine dinosaurs don't really work for this point in the Triassic and the resemblance Herrerasaurs have with Theropods was mostly happenstance or the result of the ancestral state of all dinosaurs. This animal would have been an important part of the predator assemblage in Argentina at the time, while the massive Saurosuchus and earlier Prestosuchus occupied the top predator niches in the area, Herrerasaurs were leaner animals that occupied the next rung down on the predatory niche, likely able to hunt the smaller Rhynchosaurs, Shuvosaurs and Synapsids it shared its environment with, as well as Pisanosaurus which was also alongside it. Herrerasaurus in these early years had actually found some considerable success, apparently its the most common carnivore in the famous Ischigualasto Formation where so much information about the Carnian period is known from. Integument is a controversial question for these early dinosaurs, personally I feel like we don't have good enough evidence to reconstruct them with feathers as a rule, but I'll post some images of them with and without feathers.   Herrerasaurus is known from much better material than most other contemporary dinosaurs, but as touched on the phylogeny is highly controversial, in the previous paragraph I've described what I understand to be the currently most popular position but in earlier decades they were actually thought to be basal Sauropodomorphs, and later on basal Theropods (in fact its pinballed between Theropod ancestral Saurischian a lot in the last 3 decades), and other people have even suggested that its still not actually a dinosaur and is part of a closely related but distinct group that falls outside, similar to what I've described as the likely situation for Pisanosaurus and Nyasasaurus. I'm pretty convinced that Herrerasaurus is a dinosaur that's part of a distinct, primitive group, but I just thought this should be mentioned. Either way the Herrerasaur family was very successful, other early dinosaurs like Staurikosaurus , Gnathovorax and possibly Chindesaurus have been assigned to it. These animals tend to be smaller and probably occupied a lower predatory niche with Staurikosaurus being a couple of meters long, they also show signs of being widespread with Chindesaurus, if it was part of the group, being found in North America.    I'll probably just sound like a broken record saying 'the phylogeny for these animals is controversial' for every single Triassic creature, but as mentioned this is especially the case with early dinosaurs, trying to ferret out the first theropods, especially with the increasingly common view that the Herrerasaurs are not Theropods, has been difficult, with the extra complication that some animals assumed to be Theropods have also been suggested to be Herrerasaurs, or something completely different. Its not helped that the animals involved all seem to share similar bodyplans and lifestyles, so there's likely not going to be much to say about many of these other than 'small or medium sized predator' with all that entails. Suggested highly basal Theropods include Daemonosaurus and Tawa, both of these are from North America, the famous Ghost Ranch formation in New Mexico to be specific, and are not known from good remains. I should be fair and say there's some more variation for these creatures than I implied, Daemonosaurus is a funny looking animal, at 2 meters long it has these massively oversized front teeth that stuck out in front of the jaw in a very unusual kind of way, almost like it had buck teeth, and a gap between teeth in its upper jaw. What exactly this was for isn't really clear, maybe nabbing small animals, even though this feature isn't present in similar carnivores, the type specimen might also be a juvenile considering its short skull and big eyes, and of course there remains controversy about its affinity, if it was a Herrerasaur and not a theropod, it was one of of the last such animals, getting all the way to the Rhaetian. Tawa is a bit bigger and also had a bit of a kink in its upper jaw, it was a lithe carnivore and some have suggested it could just be an adult Daemonosaurus. Another possibility is the South American Eodromaeus, a small, speedy contemporary of Herrerasaurus.     Staying in New Mexico, we can start to talk about animals that are more solidly understood to be derived theropods, and this brings us to the famous Coelophysis and its relatives, these were the first Neotheropods, the true theropods that would give rise to the rest of the animals that make up the group to the present day. Coelophysis is the Triassic dinosaur for most people, and not for nothing, we have a frankly ridiculous amount of remains for this animal, literally hundreds of skeletons have been uncovered with what appear to have been some kind of mass die off that occurred in Ghost Ranch in New Mexico (curiously, Ghost Ranch used to be owned by Georgia O'Keeffe, this'll come up again later), part of the wider Chinle formation across the late Norian and Rhaetian. Coelophysis was a long but light animal, 3 meters long but only about 25 kilos in weight, it slotted into the aforementioned medium predator role and lived alongside various Phytosaurs, Aetosaurs, Shuvasaurs, Silesaurs, and even the big top predator Postosuchus, as well as various small animals like Cynodonts or Crocodylomorphs that probably made up a major part of its diet. It was by far the most common dinosaur around, and its remains are so extensive we can get possible indications of sexual dimorphism (there's a neat, almost 50/50 divide between the skeletons as robust or gracile, likely male or female), growth stages and diet. Famously it was thought that some individuals were eating baby members of their own species based on the bones present in their abdomen, but recently what was previously thought to be direct evidence of cannibalism has been reinterpreted to be an unrelated small reptile it was eating, probably a Crocodylomorph. At this point in time Dinosaurs like Coelophysis would have been some of the most speed adapted animals in earth history up till this point, and likely had high metabolism not really comparable to anything else around. How social they were has been a longstanding question, obviously the mass remains implies a lot of time spent together in big groups, but then that could have been the result of extreme and unlikely conditions like big crowds of animals forced together because of a major drought and all killed because of a flash flood. Still, some researchers have argued they could have worked in groups to mob bigger prey items to death like you see in things like Komodo dragons today, though this would have been far from pack hunting as we think of it in things like wolves.    The close relatives of Coelophysis would continue well into the Jurassic, staying in the latest Triassic and moving to Europe, one such animal would have been quite a lot larger, Liliensternus. This animal was more than 5 meters long and over 100KG, and ranged until the very end of the Triassic, it might have had a crest on its head similar to the later Dilophosaurus, below its menacing the much larger Plateosaurus. Another such animal is the delightfully named Pendraig from Wales, much smaller than its relatives and possibly an island dwarf, and Lucianovenator from Argentina, which together show how widely ranging these early theropods were despite not being anywhere near as common as Coelophysis.    While early theropods were established by the end of Triassic, there were other dinosaurs that had found radically different niches, these are the Sauropod line dinosaurs on the other side of Saurischia, and here we get to one of the earliest known dinosaurs who's relationships have gone through considerable change over the years, Eoraptor. This animal from Carnian Argentina when first found was thought to be probably the earliest dinosaur known and additionally the first known Theropod, possessing primitive features like a four fingered hand (with the remnants of a fifth digit). Theropods quickly lost or reduced two of their fingers in their hands and later members (notably birds) went further down to just one or two. As it turns out, Eoraptor seems more likely to have actually been a Sauropodomorph than a Theropod, on the line towards Apatosaurus rather than Tyrannosaurus despite appearances. Unlike its titanic descendants it was a very small, only about a meter long, and it was also probably an omnivore with small teeth with an unusual degree of differentiation in Archosaurs that could have eaten various different things. Its affinity is still in flux, of course, and new studies might reclassify it again, but for now it seems like it was probably Sauropodomorph.  Close in time to Eoraptor you also had Buriolestes and Saturnalia, all of these animals are basically from the same place and time, with similar sizes and niches. Buriolestes does seem to have been more carnivorous, while Saturnalia was starting to shift towards purer herbivory and increasingly visually resembled the forms Sauropodomorphs were taking as the Triassic went on with a longer neck and smaller skull. They were all less than 15 kilos and might have been common prey items for the various Herrerasaurs and Pseudosuchians.   These early Sauropodomorphs quickly specialised into herbivory and accordingly their place in the ecosystem changed radically. Thecodontosaurus from the very end of the Triassic in England was a two meter long animal that was probably similar to these early herbivorous Sauropodomorphs, but soon they would get much larger, in nearby Germany you also had Efraasia, an animal that could reach more than 6 metres long and probably several hundred Kilos. As far as I know the overwhelming majority of Triassic Sauropodomorphs are believed to have been fully bipedal, contrary to older depictions suggesting that they were facultivly bipedal if they needed to rear up but quadrupedal most of the time. They had small, peg like teeth on a small head with the neck increasingly elongated, and increasingly large claws on their front limbs. Based on these characteristics, it actually seems that early Sauropodomorphs were converging on a niche that would be later filled by things like Therizinosaurs and even Ground Sloths tens or hundreds of millions of years in the future, eating plants at higher and higher elevations and using their bipedalism and large claws to pull things into feeding range.   But by far the most famous Sauropodomorph, and one of the most important animals in the history of the study of Palaeontology, is Plateosaurus, from Norian Germany and other parts of Middle Europe. These animals are known from very extensive remains, more than a hundred skeletons, and they show a wide range of morphs that range in size from about 5 meters to 10 meters, and about half a tonne to 4 tonnes. Different species of Plateosaurus were probably occupying different roles in the ecosystem to account for the size range. The discovery of these animals in abundance in the early 19th century was highly important in creating the concept of dinosaurs as being a major but extinct group of animals and its been known to science so long that we have a long history of different reconstructions of the animal and its habit, with it starting as a sluggish, lizard like animal that dragged its tail around on the ground, to then being seeing as a quadruped that could rear up on its hind legs facultatively to eat high plants or run away if needed (you see this in walking with dinosaurs), to the current consensus that it was likely a full time biped that kept its front limbs free to handle vegetation or defend itself. Its gait made it a good runner for its size, and animals like Plateosaurus were the first really massive dinosaurs, although interestingly it may not have been the biggest animal in Europe at the time (we'll get to them later). At the risk of suggesting that evolution has an intended end point, you can see most of the characteristics of later Sauropods in these kinds of animals with the long neck and tail, small head, and peg like teeth that it would have used to strip branches of their leaves. Plateosaurus was among the first dinosaurs that was really dominant in its environment, although that environment could be less extensive than might be assumed. Like Coelophysis we have enough specimens to make inferences about things like growth rates, with it seeming to have very rapid growth rates at first and, unlike mammals, it continuing to grow for most of the rest of its life, at a slower rate, even after reaching sexual maturity. This is pretty standard for Sauropods.   Sauropodomorphs are interesting because they seem to show signs that their range was heavily influenced be climate, they are very common herbivores, sometimes the most common, in areas like Europe and southern South America, but don't appear at all in the well preserved beds in North America where we find the likes of Coelophysis. The difference between these environments was generally the temperature, North America at this time was extremely hot, much closer to the equator than today, and that seems to have been quite difficult for the Sauropodomorphs that generally had higher metabolisms compared to other herbivores, but much more favourable to more ectothermic Pseudosuchians like Aetosaurs. For Plateosaurus, based on their eye structure, we even have indications they might have been more active in the evenings and mornings rather than the height of the day and the height of the heat. In South America, a number of Sauropodomorphs ended up taking over a dominant position as major herbivores, such as Riojasaurus that had similar size ranges as Plateosaurus. In South Africa Melanorosaurus occupied a very similar role, though I've heard it has some indications that it was a quadruped. These smallish, flexible Sauropodomorphs would continue well into the Jurassic in the form of animals like Massospondylus and its relatives, where they are very important herbivores in the early period of the Jurassic.   The final dinosaur I'm going to mention is Lessemsaurus, this lived alongside Riojasaurus at the end of the Norian in South America, but what really sets this animal apart is the fact that it was just massive. Estimates put a potential length for Lessemsaurus at up to 12 meters long and maybe up to 10 tons, though I have to say this was a high estimate and more conservatively it could be 7 tons. This comfortably makes it one of the largest land animals in earth history up until this point, there's only one other animal on earth at the time that could have competed, and we'll get to that later, but overall it shows that a tendency for gigantic sizes was an inbuilt feature for Sauropodomorphs almost from the start. Within about 20 million years of animals like Eoraptor coming into being, they had already become absolute titans that didn't have to fear anything else, and this trend would only continue. Some have recovered Lessemsaurus and its relatives as the earliest true Sauropods, others consider it just a close relative, but either way Sauropods would go and dominate into the Jurassic and Cretaceous, spreading across the globe and being the most important herbivorous animals in many different times and places across more than 140 million years, producing the largest animals that ever walked the earth in the form of true behemoths like Argentinosaurus and Patagotitan much later on. Even before the end of the Triassic you could see the direction these animals were going, and it would have been impossible to believe just a few million years earlier, but even then Lessemsaurus was a midget compared to its later relatives. They had a combination of features from more derived and more basal Sauropodomorphs, notably they had bird like air sacs that invaded their bones that gave efficient respiration, but didn't quite yet have the columnar, weight bearing legs and might have still had some use for rearing up and making use of longer claws.   We're going to remain with the Ornithodirans to talk about the situation for the other most famous Mesozoic animals, the Pterosaurs. As mentioned last week we don't really have a good handle on early Pterosaur evolution because of a lack of remains but we do have some good pointers, and the user Knormal was kind enough to direct my attention towards an animal that has been recently discovered that shows features that seem to be on the way towards Pterosaurs, Venetoraptor. This animal from Carnian Brazil had elongated fingers and an odd pointy beak. Its the fingers that are the big draw for it, most Archosaurs do not have enlarged digits like this, especially the bipedal ones, and the structure with the fourth digit being the longest matches what we see in Pterosaurs where the fourth digit is hugely elongated to create the structure for the wing in the first place. The finger structure has been suggested to have been an arboreal adaptation, letting it more easily hold onto branches and prey, and indeed the small size of this animal would also point towards tree living, at about the size of a racoon. I'm sure there'll be more to say about this animal in the future with more research.  Venetoraptor's potential arboreality would seem like a good starting point for an animal to become a flier, although there's no evidence of a patagium (skin surface for gliding) in its fossils. As mentioned last week, other Pterosaur relatives like Scleromochlus seem to have had curious hopping adaptations, and if an animal like Venetoraptor had similar tendencies, both in the trees and on the ground (like a Sifaki) that could have created a strong incentive to evolve some kind of gliding surface for further and further jumps, that then turned into powered flight. Unfortunately, we just have too many unanswered questions that can only really be solved with new discoveries, Venetoraptor and similar animals don't give any insight into how Pterosaurs would have gone from gliding to flapping, and it remains unclear if they really did come from arboreal ancestors or if they can from comparatively groundbound creatures like Scleromochlus that were able to hop further and further in each bound by evolving a gliding surface while running across flat terrain. Similar issues exist with bird evolution, even though its far better understood overall. Additionally, Pterosaurs have another problem, their ancestors seem to have been bipedal, but true Pterosaurs were almost certainly Quadrupedal when on the ground and used their big front limbs bearing the wings as their main mode of moving around while on the ground, we have no idea how and why this kind of transition took place based on the current fossil record. Regardless, we know that Pterosaurs were definitively filling the sky at the end of the Triassic, some of our best remains of them come from sites in Northern Italy, where favourable conditions led to rare preservation of fragile animals like this. Last week I mentioned Eudimorphodon, this was from the end of the Norian and as can be seen was already basically fully adapted to flight. Most of these early Pterosaurs were small animals with teeth and a long, vaned tail trailing out the back, quite different from how the last members of the group would appear in the Cretaceous. Eudimorphodon was no exception and seems to have been about a meter in wingspan and mostly ate fish. We tend to have fish eating Pterosaurs hugely overrepresented compared to more terrestrial ones simply because aquatic sediments are just at preserving things in general, so there's a lot preservation bias going on with Pterosaurs in particular. Eudimorphodon's teeth were actually notable in being better at crushing hard bodied animals like shellfish compared to the Pterosaur norm.  Other early Pterosaurs include Peteinosaurus and Preondactylus, both from Norian Italy. These were still small, only about the size of a magpie or even smaller for Preondactylus, they both were probably orientated towards eating small insects they could catch on the wing, among the first animals in history able to do this kind of aerial predation. Pterosaurs may not have been quite as impressive or diverse at the end of the Triassic as they would later become, but we can't understate just how revolutionary these animals were, they were far and away the earliest flying tetrapod, tens of millions of years earlier than birds and bats, finding and occupying entirely new niches than anything seen before all the way to the end of the Cretaceous and the mass extinction that laid the groundwork the Cenozoic, 66 million years ago. In that time they would diversify massively, including evolving the largest flying animals ever, creatures comparable to small airplanes. Again I just think that's really indicative of how much radical change was going on during the Triassic that was felt throughout the ages afterwards.    Of course, I don't want to give the wrong impression that by the late Triassic it was just a Dinosaur and Pterosaur show, the other animals we have previously discussed, especially the Pseudosuchians, were absolutely still around and remained dominant in all kinds of different niches and environments. Of particular note are the big carnivorous niches, dinosaurs still had a way to go because massive monstrosities like Fasolasuchus were terrorizing the landscape at the end of the Norian. This animal was probably just outside the Rauisuchians, but holds the distinction of likely being the largest land predator ever that was not a Theropod dinosaur, eclipsing contenders like Saurosuchus a few million years before and Barinasuchus more than 200 million years later (all animals are Pseudosuchians, natch). Its conceivable that Fasolasuchus was almost 10 meters long and reached up to 3 tons, comfortably matching or exceeding a number of large theropods like Allosaurus and Albertosaurus. Its size was no accident, it comes from the same Norian age formation in Argentina as the aforementioned Lessemsaurus, leading to speculation that it was pressured into increasing in size so that it could prey on the increasingly large Sauropodomorph dinosaurs that increasingly made up the herbivore clades in the area, while also letting it eat things like the still existing dicynodonts as well. This kind of pressure probably also accounts for the supersizing of Dinosaur predators much later into the Mesozoic as herbivorous dinosaurs got bigger and bigger.   While Fasolasuchus was barging around Argentina, up stateside you had the smaller Postosuchus. This actually was a true Rauisuchian, and interesting recent studies have indicated that it was bipedal, at least as an adult, contrary to traditional interpretations, giving it a very curious look as kind of low slung croc-dinosaur thing, as we know this wasn't really all that unusual for Archosaurs but I think I'm just used to thinking of the Walking with Dinosaurs version of this animal so it feels wrong somehow. Not that it cared very much for what I think, at about 5 meters long and potentially over 300KG it was the largest predator around and comfortably outclassed nearby dinosaurs like Coelophysis, with a massive skull vaguely shaped like a big theropod's. It would have been able to prey on most things in Norian America, with the largest potential food item possibly being the Dicynodont Placerias, as well as the Aetosaurs, for which was probably a main reason they had their armour and neck spikes. Meanwhile, in Germany we had another large Rauisuchian that was probably about 6 meters long and likely preying on the numerous Plateosaurus that it lived alongside, as far as I know this animal is presumed to have been a quadruped but then there hasn't been much work on its stance.    The next creature involves another change of scenery, to latest Triassic Poland, and a recently discovered and very unusual animal, Smok. Poland has in recent years turned out to have some very good extremely late Triassic fossils that have been uncovered, and what's been found has been quite unexpected for the time and place. Smok wawelski(named after the Wawel dragon) in particular fits the standard of being a Triassic animal that they have no clue on how to classify, its been considered both a Pseudosuchian and a Dinosaur by different researchers, not helped by what looks to be a strongly bipedal stance at a time when everyone and their mother was trying out standing on two legs. Since its a recently discovered animal hopefully this will be resolved to some degree in the near future with more work, but the broad consensus seems to be that it wasn't a dinosaur, just converging harder than almost any other known animal with them. Of note is the fact that its arms are very long compared to dinosaurs, but its braincase is similar to dinos and its hips (usually a good way to determine what's related to what, as we have seen) is hilariously frustratingly almost exactly half Dinosaur and half Pseudosuchian. Whatever the case, it was certainly the top predator in its environment, far above uncontroversial Dinosaurs and Pseudosuchians, able to prey on dicynodonts and other animals, with an indication that it could crush bone to get more nutrition. There's even some signs based on footprints that Smok or an animal like it could have survived into the earliest Jurassic.   I have one more of these many many two legged carnivores I want to cover, and this lets me finally put a capper on a group that's been with us since the start of this series, the Poposaurs. Somewhat ironically, the titular Poposaurus only appears near the end of the Triassic after its various diverse relatives, and as Poposaurs loved to do it didn't much in common visually or habitually with its close relatives, despite not being closely related at all it strongly evoked Postosuchus and its relatives in being a low slung, bipedal predator from a recently quadrupedal ancestor. It was smaller though, probably maxing out at around 100 KG, putting it halfway between Postosuchus and Coelophysis that it lived alongside. Since it almost certainly had a more croc like appearance, sort of amusingly it was a bit like a real life version of the bald Jurassic Park velociraptors with a very long tail with a curious hump near the start. In addition to Poposaurus, we also had the closely related Shuvosaurs, with the last member of the group from the latest Triassic bringing things back around to Georgia O'Keeffe, Effigia, with the specific name Okeeffeae after the previous owner of Ghost Ranch in which it was found. This was a far smaller animal compared to the giant Sillosuchus, only a meter or two long, but it still found a place as small, herbivorous lookalikes to Ornithischians later on. Thus we can finally close the book on Poposaurs.   Meanwhile, back in the water, the Phytosaurs were still going strong and reached some ridiculous sizes, again. In North America Redondasaurus and Smilosuchus made crossing a river a game of russian roulette during the latest Triassic. Redondasaurus was about 6.5 meters long and had these curious looking raised spines all along its vertebra, like a slight sail with armour on top, its the latest known Phytosaur we have evidence for. Smilosuchus Gregorii was even larger, potentially the largest Phytosaur with lengths that could have reached maybe 12 meters in some species, placing it alongside the massive crocodilians like Purussaurus and Deinosuchus much later on, but more conservative estimates pull it down to about 7 meters, and its worth keeping in mind that Phytosaurs had longer tails than crocodilians. Regardless, It would have been capable of eating anything in its environment at these maximum sizes, including the large Dicynodont Placerias if it was so inclined. We even have evidence of some kind of large Phytosaur making an attack on a Rauisuchian based on a tooth lodged in its femur, albeit the Rauisuchian survived the attack. It seems as though Phytosaurs like this were more inclined to slash and cut into their victims based on their cutting teeth to try and kill them with lacerations and blood loss compared to the modern crocodilian strategy of simply grabbing them and holding them underwater until they drowned.    Phytosaurs were diverse, not all of them were big animals ripping into prey from the shore. Even within the Smilosuchus genus there was also Smilosuchus adamanensis, which was a smaller animal with narrower jaws more specialized into eating fish than land animals. Meanwhile in Europe Mystriosuchus was also adapted into a Gharial like body plan and interestingly seems to have been another Phytosaur that became highly marine, based on some fossils found in marine sediment, with others in freshwater environments. But most curious was an animal that seemed to go the exact opposite direction, Nicrosaurus, also from Germany, took a novel step and seems to have gone back to being a terrestrial predator, losing some aquatic adaptations in favour of longer legs and a deeper skull that would have been better for land predation, though with some possibility it was still favourable towards the water. It was about 5 meters long at max and probably could have gone after small Sauropodomorphs or Silesaurs, it also had a big conspicuous crest that could have been for display or intimidation. For a group of animals mostly known for their convergence with Crocodilians, its pretty funny that they took that all the way towards even converging with the Crocs that abandoned being aquatic predators in favour of being land predators like Sebecids. I suppose some things never go out of style.     To touch back on Pseudosuchians more gentle herbivores, Aetosaurs were still going strong until the end of the Triassic, as mentioned above hotter areas did not seem to be favourable to big herbivorous dinosaurs and in their place there the Aetosaurs tended to proliferate, although they also lived alongside each other elsewhere. Typothorax was very common in late Triassic North America with its armoured scuts being found all over the place, and had a wide range of sizes a bit like Plateosaurus elsewhere, small individuals were probably about 2 meters long, while the largest could be up to 6 meters ling, the biggest of all Aetosaurs. Its body looks almost comically wide, even as far as the generally wide Aetosaurs go, and particularly contrasted with its tiny little head. It also had big spikes projecting out of its, er, rear area around the Cloaca, why exactly it needed these I don't want to speculate on. In addition to Typothorax, North America also had smaller species like Garzapelta, which has been recently uncovered from a well preserved specimen in Texas. These animals had a row of spikes running down the sides of their armour with enlarged spikes on their necks, to help complete their armour and fend off attacks from any impulsive Pseudosuchian. Over in Germany you had the actual namesake of the whole group, Aetosaurus, a small animal only up to a couple of meters that was a slightly more basal and possibly social member (a large conglomerate have been found together) without the additional row of spikes. Recently, its actually been suggested that this animal is really a close relative to Typothorax and is in fact a juvenile form of another, larger animal called Paratypothorax, which would account for its unpronounced features that could be mistakenly interpreted as primitive. Either way, this would have lived alongside the likes of Plateosaurus, in addition to the various Silesaurs and Synapsids, suggesting that these herbivores weren't necessarily competing against each other but found different niches in the environment to occupy, or that Aetosaurs might have supplemented their diet with insects and carrion.     The last word I'm going to give on the Pseudosuchians and their near relatives is to revisit the ancestors of their living members, the Crocodylomorphs. At the near the end of the Triassic at least one species, Redondavenator seems to have gotten quite large, up to four metres, probably to take over a role left open by absent Rauisuchians, but this animal was short lived. More typically, by the very end of the Triassic you still had the small, bipedal, leggy croc dogs, one of the best examples being Terrestrisuchus from wales, eating insects and not even reaching a meter long despite its lengthy tail. Closely related you had Saltoposuchus, of which it has been suggested Terrestrisuchus was a juvenile form, but I don't think that idea is currently popular since the timeline does not add up at all since Saltoposuchus was Norian. These would be the only Pseudosuchians that would manage to survive into the Jurassic, the gracile forms would stick around for a while but increasingly you had forms that got bigger and resemble modern crocodilians, albeit still not really showing signs of being aquatic, with the most notable species being Protosuchus from the North America and Africa, roughly the size of a Doberman. Crocodilians as we all know ended up being some of the great survivors of the Mesozoic, despite their humble beginnings making it through thick and thin to be very important, if radically different, members of today's biosphere when all of their much more ostentatious cousins in the Triassic had died off.     Now, as we've overwhelmingly covered Archosaurs, and since I've repeatedly talked about Archosaurian success, its all too easy to forget about the animals that we opened this whole series with, the Synapsids. Broadly its true to say that Archosaurs displaced them from key roles in the ecosystem like intermediate predators and most herbivorous roles, but I want to be very careful about this because, in all too many books and documentaries on this topic, this notion gets pushed much too far with this idea that Synapsids petered out into tiny, unimportant rats as they were outcompeted by the superior archosaurs and especially dinosaurs, with the Dicynodonts just sliding towards oblivion in the face of the just plain better Archosaurs. This is a simplistic take the best of times, but recent discoveries have further shown how wrong it can be, in fact it seems to be the case that in significant parts of the world, Synapsids including Dicynodonts remained very important parts of the ecosystem and didn't just whither and die in the face of dinosaurs, but adapted and changed themselves. In North America, as mentioned last week Placerias was still cruising around through the Norian period, in a continent famous for its lack of Sauropodomorphs, and there have been indications that other species of Dicynodont lived alongside it. Likewise at the same time in Argentina you have Jachaleria, a cow sized animal that might have been living alongside the massive Lessemsaurus and Fasolasuchus. Then in South Africa it has been recently determined that a creature called Pentasaurus (can't find a picture sadly), who's affinity was controversial for a long time, was probably a Norian aged Dicynodont who seems to have lived alongside Sauropodomorphs without much issue.   But far and away the most astonishing development has been the discovery of the massive, Polish Dicynodont Lisowicia. This is one of my favourite animals of the entire Triassic, it's from the same latest Norian, early Rhaetian formation as the aforementioned Smok, as noted earlier Poland has been churning some of the most unexpected and important recent discoveries from the latest Triassic and Lisowicia is emblematic of that. This was the largest Dicynodont ever, and one of the largest Synapsids of all time, holding the record until the emergence of Rhinocerotoids like Paraceratherium more than 160 million years later. Its estimated to have weighed at least 5.5 tons, probably going up to 7 or 8 tons in higher estimates, 4.5 meters long and 2.5 meters tall, comfortably in the size range of a large living African elephant. The only larger animals that existed on Earth at the time might have been the aforementioned Lessemsaurus over in Argentina. Interestingly, despite Poland being in close proximity to Germany and Plateosaurus, there's no firm evidence that Sauropodomorphs lived in the area, implying that big Dicynodonts like Lisowicia was already occupying the niches of giant herbivores, or that the generally swampy environment of the area was unfavorable to Sauropodomorphs but well suited to Dicynodonts. Like its relatives, Lisowicia had lost its teeth entirely and had adapted its beak into a large phalanges that resembled teeth, and might have been used to fight each other or dig through the soil. Smok was almost certainly the only animal capable of threatening it, but even then it could only really go for juveniles. Interestingly, unlike other Dicynodonts its legs are positioned fully underneath its body in an erect stance, probably an important adaptation to let it carry its bulk. Just like with Dinosaurs its amazing seeing the change in size from the likes of a cat sized Kombuisia at the start of the Triassic to these elephant sized behemoths by the end.   On the exact opposite end of the size spectrum, Cynodonts were undergoing a general trend towards miniaturisation as the Triassic neared its end. There were still quite large Traversodontids like the pig sized Scalenodontoides, that formed part of the herbivore or omnivore assemblage in places like Rhaetian South Africa, but on the Probainognathian side more relevant to us specifically they were continuing to diversify as they slotted into new niches as dominant small animals. At the very end of the Triassic a curious new group would emerge, the Tritylodontids. These were generally small, herbivorous animals that reached a few kilos and are mostly only known from their distinct three cusped teeth, and sometimes jaws. One of earliest members would have been Oligokyphus that was found in many different places like Europe, China and North America from the Rhaetian into the early Jurassic. It was probably similar to rodents in many ways, eating things like nuts and seeds and other high calorie but tough plant material to get what it needed, some of the earliest small animals to specialize in this kind of food. Tritylodontids lost their canines and had large incisors for nipping and molars for chewing, very similar setup to rodents and might have also had their teeth grow continuously. They were also resilient, lasting all throughout the Jurassic well into the Cretaceous, in fact another Triassic Cynodont lineage touched on last week, the Tritheledontids including animals like Riograndia, would also survive into the Jurassic well past the Triassic extinction, evidently there were multiple non-mammal Cynodonts that made it over the boundary, probably showing how successful they really were as small herbivores and insectivores.   However the Cynodonts that prompt the most interest will always be the Mammaliaformes, as mentioned last week these had started to appear at the tail end of the Triassic, Morganucodon is a crucially important animal with it showing up in the Rhaetian in places like Wales and China, at about 10 centimetres long, based on the remains we have this genus was very common compared to other comparable Mammaliaformes. We can tell that it was close to mammals based on its advanced jaw structure, its jaw was now almost solely the dentary bone with the other bones being increasing diminished and pushed to the back, forming part of the joint. As mammal evolution marched forward, these previous jaw bones would get completely repurposed, turning into the middle ear bones (malleus, incus, and stapes) that helps give mammals such incredibly advanced hearing relative to other animals, which would prove to be a key adaptation for nocturnal life. This was still an ongoing process for Morganucodon but already it was probably assisting in its hearing. Its even been suggested that the toothless state of Morganucodon's young is indication that they were milk drinking, showing that this adaptation that's near impossible to fossilize that makes modern mammals might have already been present, animals like Morganucodon were likely to have been egg laying like Monotremes as well. Morganucodon was almost certainly a dedicated insectivore. Another important latest Triassic Mammaliaform is the mouse sized Megazostrodon, which has been found in France during the Rhaetian. All of these creatures maintained their advanced dentition with two sets of teeth over their lifetimes divided between Incisors, Canines and Molars, which worked well for catching and grinding up hard shelled insects, while their increasingly small size and tendency towards nocturnality, facilitated by good hearing, a good sense of smell, small size, warm bloodedness and burrowing adaptations would carve out the path mammals took for the next 140 million years as these animals settled into humble niches in the shadow of the much more ostentatious dinosaurs around them.  
khwarezm fucked around with this message at 01:23 on May 14, 2024 |
|
#
?
May 13, 2024 19:25
|
|
|
  Its finally happened, I've had to split this weeks post into two, and not for no reason. While I've covered all most of the most charismatic groups in the previous post, primarily Dinosaurs, Pseudosuchians and Synapsids, there's a lot more I want to touch on as we bring the land life of the Triassic to its conclusion, particularly with groups that tend to get less attention in popular culture overall, including some I covered in the first post. I also want to give a run down on the state of the earth as the world moves into the Jurassic, in particular a major mass extinction event that marks that transition and the ramifications of it. To begin, lets look at a particularly bizarre group of animals I teased last time, the Drepanosaurs. So these Diapsid reptiles were some of the various animals that became strongly arboreal as the forests expanded again over the course of the late Triassic and they seem to have turned into some kind of Monkey/Chameleon/Sloth/Koala... thing? Advanced Drepanosaurs like Drepanosaurus itself and Megalancosaurus are known from places like New Mexico and Northern Italy, with the latter location being a good source of smaller Triassic animals like Pterosaurs we have already covered. These animals had long, prehensile (gripping) tails that you see in things like Spider Monkeys and Chameleons today, as well as bird like heads full of small teeth, a claw like structure at the end of the tail, a small hump over its shoulders from enlarged vertebra, and big, grasping front limbs with opposable digits to hold onto branches. Compared to its relatives Drepanosaurus (which was one of the larger members of the group at about 50 centimetres) massively enlarged its front claws, with one particular talon looking almost comical in how large it had gotten. The actual structure of the arm is completely unique and not seen in basically any other kind of animal, as can be seen below. It was extremely beefy and very rigid without much range of movement, but seems to have been capable of very powerful scraping motion. The claws might also be the reason for the strange hump like structure on its back since this may have been important for attaching the muscles needed to give more power to the claws. Its been suggested that for Drepanosaurus, the overall build of the animal and claws suggests a certain amount of convergence with small, arboreal anteaters, leading to the suggestion that it was using its huge claws to dig out insect larvae from underneath tree bark and eat them, but seemingly with far more power and force than any living animal. The other Drepanosaurs with less extreme claws were probably still arboreal insectivores with a similar niche to Chameleons today. One species, Ancistronychus from New Mexico, has been suggested to have adapted its own large claws to live more on the ground and dig up burrowing insects and insect nests to eat, or burrow itself for safety.      The affinity of such strange animals is very hard to place, they are only really sure to be Diapsids but beyond that its hard to say. For some time they were suggested to be Archosauromorphs, possibly related to Tanystrophids, in addition it was also suggested they were related to the Permian, gliding Weigeltisaurids, and the Triassic gliders we have mentioned last post the Kuehneosaurids, but increasingly its been suggested that they are very basal Diapsids that diverged far back in the Permian, perhaps still close relatives to the Weigeltisaurids. Even the more basal seeming members of Drepanosaurs we have found in the late Triassic still seem very odd, most notably the tiny Hypuronector from Norian New Jersey that had highly enlarged, leaf shaped tails that were initially interpreted to be signs of an aquatic lifestyle. Later, it was determined that they were actually arboreal as well, whether the tail had much pragmatic function or was more a sexually selected is hard to say, but some elements of the animals limbs have led to suggestions it was actually a glider, though no direct signs of a patagium have been found.   Back in the Triassic, there were other odd Temnospondyl amphibians to contend with. In the waters of Germany and Poland alongside the likes of Lisowicia, the pancake shaped Gerrothorax To go from the bizarre to something more familiar, we know that by the end of the Triassic more modern reptiles were emerging. The living Lepidosaurs consist of the overwhelming majority of animals recognized as Reptiles, Lizards, Snake and the Tuatara, and these first arise in the Triassic, with Sophineta probably close to the common ancestors. Despite their appearances, Tuataras are part of a distinct subgroup that split off from other Lepidosaurs about 240 million years ago, the Rhynchocephalians, making them drastically removed from living lizards. Rhynchocephalians were far more important and abundant during the Mesozoic than they are today, and they first started to proliferate during the Triassic with early members of the group including Clevosaurus who's remains have been found all across the world from the Carnian to the early Jurassic. This animal was about 12 centimeters long and like mostly ate insects and plants. Meanwhile, one of the earliest animals that was probably a squamate (modern lizards and snakes) or something close is Megachirella, from the mid Triassic in Italy, probably also eating bugs. Its strange to think that something as seemingly basic as a lizard didn't evolve until well into the Triassic but this was the case, and Squamates wouldn't actually become dominant reptiles until much later on, with their remains being extremely rare while in comparison Rhynchocephalians occupied most of the niches they did, and would do so well into the Mesozoic before being whittled down to their current range only in New Zealand.    In addition to Squamates, the final group of recognisable modern reptiles that we haven't touched on have their origins in the Triassic, the Turtles. Turtles have had a highly controversial taxonomic history, for a long time it was believed that they were the most basal of all living Amniotes, the last surviving Anapsids with no distinctive holes in their heads unlike Synapsids and Diapsids. However, genetic analysis has proven this not to be the case, it seems that they are actually diapsid reptiles that secondarily lost their holes and are probably most closely related to Archosaurs, making them much more derived than previously thought. The fossil record for turtles has been typically poor, but some newer discoveries have helped fill in old gaps and show how they started to gain their distinctive armoured shell that has served them so well for so long. There's some indications that testudines might have been around since the late Permian with an animal called Eunotosaurus, and increasingly evidence is pointing towards it being ancestral to turtles, but overall we can only definitively talk about the Triassic, they seem to have been closely related to the marine Placodonts (which will be covered in far more detail in the near future) that also had a lot of focus on armour. A potential early Triassic precursor to turtles is Pappochelys from Ladinian Germany, this small reptile shows some of the beginning signs of modern turtle armour, with its enlarged rib bones forming a sort of plate armour across its abdomen, interestingly one individual even shows signs of bone cancer. Its hard to tell if this animal might have been aquatic, the environment its found in suggests it was, but its body doesn't have many adaptations for life in the water, and its been suggested that it was quite fossorial, with the bones that would turn into the lower part of the shell enlarging here to help support digging muscles. Moving forward a few million years we come to Chinese Odontochelys, this animal seems to have been far more aquatic, and interestingly it seems to have had the bottom half of a turtle shell (the Plastron), but not the top (the Carapace), instead relying on the armoured ribs to achieve the same means. This turtle is also one of the last ones that had teeth. The final animal here to talk about is latest Triassic Proganochelys from Germany, this is considered the first turtle that would have been unmistakable as a turtle, with a fully developed shell with both a Plastron and Carapace, although it couldn't draw its head into its shell like modern turtles and instead had some additional spikes near its neck for extra protection (like Aetosaurs!). The path from animals like Odontochelys to Proganochelys is quite opaque and needs more resolution, there's confusing features like the dentition (living turtles have no teeth, early turtles have both toothed and non-toothed representatives without a clear continuum, making it hard to pin down when they were definitively lost in favour of the beak) and how aquatic they are. Its been suggested that turtles evolved as burrowing animals first and foremost, which helped facilitate their strong shells that resulted in heavy armour that protected them but also limited their mobility and breathing ability, and by happenstance aquatic life helped them overcome these kinds of issues while still keeping the shell, helping push turtles repeatedly towards living in water as we see today. Proganochelys itself might have been at least semi-aquatic and was quite large, over a meter in length, possibly having a fairly herbivorous diet as is often seen in living turtles. Stem turtles just outside of modern living turtles having split all the way back back in the Triassic were around until shockingly recently and we've covered them before, the giant Meiolaniids that only went extinct in the last 3000 years in Oceania were the last of these creatures, how narrowly they missed making it to the finish line.    The last reptiles I might mention is just a reminder that the Procolophonoids, those oft forgotten remaining Parareptiles that used to be a big deal in the Permian, managed to make their way all the way to the end of the Triassic with Hypsognathus from the Eastern US being quite common. This animal resembled a lizard but was generally herbivorous, and its bizarre cheek projections would have set it apart, a more heightened version of the features seen in its ancestors. These spikes might have helped the animal anchor itself in burrows to make it hard for predators to extract, or it could have just been for display. A similar throwback is the Allokotosaur Puercosuchus, this animal comes from New Mexico in the Norian and is much younger than most members of the group, while also having different habits. Unlike its broadly herbivorous relatives it seems to have shifted back towards carnivory, as part of the Malerisaurs, its habits and size were comparable to that of a fairly large monitor lizard.   We can also turn our eyes back to another group from the first post we couldn't revisit earlier, Amphibians. A lot of the giant Mastodonsaurs had been displaced by the likes of the Phytosaurs but the family actually continued to the end of the Triassic with the latest species of the genus Cyclotosaurus making it to Rhaetian Germany. This animal could have reached 2.5 meters long and maintained the same comically large head ideal for cramming in just about any food item it encountered. The Trematosaurs continued unabated as well, with Metoposaurus and Anaschisma in Norian Europe and America respectively being common sights in the waterways, these roughly 3 meter long animals seem to have increasingly been adapted to stay at the bottom of bodies of water, with a flattened skull to facilitate this, quickly gulping up prey items that strayed too near and camouflaging to avoid predators like Phytosaurs. They seem to have been prone to dying in large groups when the bodies of water they depended on dried up with a large number of individuals within them all perishing and being preserved. Within the Trematosaurs, the Chigutisaurids and Brachyopids actually managed to survive the end Triassic extinction, unlike their Phyotosaur competitors. This lineage lasted much longer in the colder southern continents like Australia and Antarctica then might first be assumed, with the likes of the 500 kilo Koolasuchus making it all the way into the early Cretaceous 80 million years later, preserving the role that the Temnospondyls had had for hundreds of millions of years as a top order aquatic predator lurking in the lakes and rivers for any unwary prey, until they finally went extinct soon into the early Cretaceous, ending this resilient dynasty.     To return to Triassic Temnospondyls, one particularly odd group were the Plagiosaurs. These bizarre creatures evolved an exceptionally flattened body, the likes of the pancaked Gerrothorax took this to the extreme, achieving an almost flatfish like body form that let it stay at the very bottom of a river or lake to blend into the sediment with only its raised eyes potentially giving it away, and letting it quickly suck up anything else that swam by before being noticed. Its skull was very odd to facilitate this, with the lower jaw mostly staying in place while the motion was occurring and instead the upper skull moving to create a high angle rapidly to pull in water to create a suction effect, with a novel arrangement on the skull hinge in the back to allow for this, a very unusual feature in tetrapods. It was about 1 meter long, and it seems to have lasted a very long time, about 35 million years to the very end of the Triassic with very little change in places like Germany, Greenland and Sweden. These amphibians would have been almost useless on land with their flattened, aquatic adaptations, small limbs and weak vertebra, accordingly its been suggested that they might have retained neotenic features like external gills similar to living Axolotls to facilitate their lifestyle, but recent research has pushed against this idea. Other members of this family had very similar features, like the larger and earlier Plagiosternum.   Rounding out the amphibians, as mentioned in the first post at the start of the Triassic we seem to have modern Lissamphibians with the frog like Triadobatrachus, but after that their fossils are sparse, though with some evidence from the Chinle formation. However, one animal we do have some recently uncovered evidence for are possibly the earliest Salamanders, in the form of a creature called Triassurus from Carnian Kyrgyzstan, making it definitive that these animals are at least Traissic in age with a potential divergence from Frogs maybe going much further back. Interestingly, we also seem to have signs of early Caecilians or animals like them, these worm like animals are quite distinct from frogs and Salamanders and a suggested very early member of the group is Funcusvermis, from Norian Arizona. This animal shows potentially transitional features retaining small legs and much more well developed eyes compared to living Caecilians, but still showing the snake like body shape that was going to become the Caecilian trademark. Later, more solidly assigned Caecilians from the Jurassic show they still had limbs a few tens of millions of years later, making it easy to suspect that an animal like Funcusvermis could be ancestral. Another curious animal worth mentioning is Madygenerpeton, this seems to have actually been a Reptiliomorph, the amphibians that were very close to amniotes in their relationships but not quite all the way there, likely not quite able to lay Amniote eggs and still dependent on the water. These accordingly would have been distinct from all other amphibians and reptilians, having reached the highest diversity at the end of the Carboniferous into the Early Permian, but still hanging on in the late Triassic Kyrgyzstan. Despite technically being Amphibians they would have appeared much more like lizards and even have had water sealing skin and armoured plating like Crocodiles, an interesting throwback animal from a transitional stage that still found a place for itself.    The last group of creatures is among the most important, but hardest to talk about, the Arthropods, with a particular focus on the Insects. Small land arthropods are always difficult to study because they don't fossilize well, and the Triassic has poor amber deposits (though the first that preserves trapped organisms) so we have a weaker record compared to later eras. Despite this we can still make interesting inferences, as mentioned in the very first post insects seem to have been hit quite hard by the Permian extinction, which is fascinating because that's one of the only times in Earth history that a major extinction event managed to considerably afflict insects, that otherwise are extremely resilient animals to such upsets. There's various lines of evidence that point towards this, first are just a general drop in insect fossils during the Permian crisis, which show a complete extinction of some previously very successful groups like the Palaeodictyoptera (which had these weird mouthparts to stab and suck plant juices) or the infamous Meganisoptera (Griffin Flies like Meganeuropsis), but there's also trace fossils that show these changes too, one study noted that the collapse of forests during the extinction decimated wood boring beetles that we know of mostly from the holes they left in trees, with such beetles almost completely disappearing through the early Triassic and only showing again, likely having had to re-evolved from completely new lineages since the old ones were all dead, with the recovery of forests during the mid Triassic. This was significant because wood consuming animals like this are crucial to effective cycling of nutrients in forests, it show how badly damaged the biosphere was that they just kind of vanish for a while. Its actually a subject of much debate about just how bad the Permian extinction was for insects, with some arguing they got through it reasonably well, but even so, its generally believed the suffered a drop in diversity and numbers and considerably diversified in the aftermath.    When talking about Triassic insects, its kind of easier to talk about what wasn't around. A lot of familiar insects hadn't evolved yet, in large part because other types of organism and environments they depend on hadn't come into being either, particularly flowering plants. A lack of flowers means a lack of niches for things like nectar feeding insects, accordingly we don't see true butterflies (Lepidoptera) with only their relatives the Caddisflies being around, Butterflies show up in the Jurassic. Similarly, the main members of the order Hymenoptera weren't evolved yet, no bees, ants or wasps (yay?), the only members of the group that lived during the Triassic were the more basal Sawflies that the others descend from. Termites and true Cockroaches (Blattodea) don't seem to have existed either, in fact there's no evidence of any of the famous Eusocial animals we have today between the likes of termites, ants and bees, these kinds of advanced social adaptations would appear much later into the Cretaceous, first in Termites, then in Hymenoptera (and uh, later on again in Mammals like Mole Rats, of all things). There could have been some other groups that developed some form of Eusociality, today we find it in a few species of weevils and thrips, but we have no real way of knowing and certainly there's no sign that there was anything having such monumental impacts on their local environment that ants and termites with super organized social structures can have today. Its kind of bizarre to think that such an important element of contemporary earth life like a termite mound just didn't exist when the first dinosaurs and mammals were around but that seems to be the case, when these kinds of insects did appear and spread they helped support bizarre new lifestyles for animals specializing in eating ants and termites much later on, like Alvarezsaurs and our current day Anteaters and Pangolins. Having said all of that, I should still keep in mind that, as mentioned, there was a lot of diversification in Triassic insects. As mentioned beetles recovered and diversified hard after the mass extinction, as did true bugs (Hemiptera), crickets and relatives (Orthoptera) and Mayflies and Dragonflies (Palaeoptera). Additionally, as mentioned this is the earliest point we find Hymenoptera with the appearance of Sawflies, butterfly ancestors with Caddisflies, as well as the first appearance of the true Flies, Diptera. We have good evidence from places like China, Kyrgyzstan, France, Argentina and Italy of insect diversification in the later Triassic, and not just insects, we've found fossils of primitive spiders like Rosamygale in Mid Triassic France, which was related to funnel web spiders today. For other Arachnids, In Italy, as mentioned we have the oldest evidence of animals preserved directly in amber, consisting of the Gall mites Triasacarus and Ampezzoa, that would have sucked on plant juices.     Its kind of hard to get information on insects from this era, I think there's a broad lack of interest since its after the famous massive insects of the Paleozoic and before the really impeccably preserved species locked in Amber that appear in the later Mesozoic and Cenozoic, but one particular insect I want to finish on is probably the one that's gotten the most attention, the ridiculously named Titanoptera Gigatitan. While it sounds like it should be in a Toho movie, this was actually part of the Titanopterans, a lineage of massive insects closely related to Grasshoppers that seem to have occupied a predatory niche comparable to Mantises (which themselves are closer to cockroaches and termites). Their front limbs, like with a Mantis, had evolved spiny protrusions and a crushing motion that would have let quickly kill and tear up its prey. These insects actually evolved in the Permian, but Gigatitan from Triassic Kyrgyzstan is most famous, reaching ridiculous sizes, with an up to 40 centimetre long wingspan and weighing almost twice as much as the largest living grasshoppers, its one of the largest insects after the Permian period from any point in history. Its so large its wingspan exceeds that of any living insect, and its not clear if it was actually capable of powered flight anymore and might have just glided. It was probably big enough to prey on small vertebrates it shared the trees with like Longisquama or Sharovipteryx, and it even made sounds with a similar structure as living grasshoppers, with a deep sound from it size almost making it sound like a bird.   Unfortunately for most of the animals we have covered, even including the Gigatitan here, we come to the final act of the Triassic and the end of one of Earth's most bizarre periods. Pangaea at this point was on its last legs, Northern Eurasia and China was always more tenuously connected to the rest of the supercontinent and high sea levels seems to have likely divided it from the rest of the Supercontinent near the end, but a bigger issue was the formation of a major rift zone that was starting to tear out North America from the conglomeration of land, at which point going into the Early Jurassic the beginnings of the Atlantic ocean begin to open up. North America and Eurasia would then form a sort of 'megacontinent', Laurasia, that counterbalanced the southern megacontinent of Gondwana, still a massive landmass consisting of Africa, India, Australia, Madagascar, South America, New Zealand, Arabia and Antarctica. The opening of a permanent, deep body of water between Laurasia and Gondwana put an end to animals being able to range across most of the world without an ocean getting in the way, which prompted greater and greater regional variation and endemism as the continents got increasingly isolated from each other.   While it would take time for North America to actually detach, the titanic geological forces at work were spelling trouble for the entire world. the force of geological and volcanic activity in the area that was starting to form the first signs of the Atlantic created violent vulcanism that was turning into a full blown large igneous province, bringing to mind nightmarish flashbacks to the processes that led to the Permian mass extinction fifty million years prior. Unfortunately a similar outcome was going to be the result of this, one of the big five extinctions, the Triassic-Jurassic extinction. This extinction is actually quite unusual, its mostly not payed attention to in the popular imagination that focuses far more on the end Cretaceous and end Permian extinctions (despite this one also involving dinosaurs and mammals), and tends to be left out of the layman's understanding of the Mesozoic and the rise of the Dinosuars, but it was extremely important in their elevation to the top animals on land. Additionally, the extinction is quite odd because its one of the only major mass extinctions that seems to have effected land life more heavily than marine life, usually its the opposite with marine ecosystems proving vulnerable to exceptionally destructive deoxygenation and acidification crises that come with the other downsides of dramatic global warming that tends to less heavily afflict land life, in both the Permian and Cretaceous mass extinctions marine life got hit harder than land life as a result, as well as the Devonian and Ordovician where most life was Marine anyway so its a bit of a moot point. That wasn't the case for the Triassic extinction, not to suggest that Marine life wasn't hit hard, but we'll get to the ramifications on marine life specifically in the next week or two on my posts on the Triassic seas. Suffice to say a lot of long standing groups and marine reptiles died, but just as many survived, far moreso than would at the end of the Cretaceous. There's also been some argument about the causes of extinction, as with every mass extinction, with some people putting forward alternative hypotheses like the ever popular asteroid impact theory. There actually is a major impact in the late Norian that created the Manicouagan crater in Canada (below right), which has become very visible since the the reservoir has filled in, but the dating for this impact, while large, is more than 10 million years out of step with the end of Triassic. Its actually funny, despite the popularity of asteroid impacts as a cause for mass extinctions they usually have very little evidence to hold it up when you look into it closely, the only one that I can think that's almost certainly associated with a major extinction is the famous Chicxulub impact at the end of the Cretaceous, and I think that might have been a very exceptional event that was absolutely not the norm, but because its associated with the most famous and recent (well, second most recent increasingly) mass extinction this might have primed people to assume that most of them can be connected with an impact. Some other scientists have argued that the suddenness of the Triassic extinction has been overstated and that it was a more drawn out thing, questioning its validity as a mass extinction at all. The patterns are certainly quite confusing as we have touched on already, but I don't think this is a very popular notion. Generally its accepted that in the process of rifting in what would become the Atlantic created the Central Atlantic Magmatic Province over a huge area of central Pangaea, causing ruinous destruction and mass release of CO2 and other gases that contributed to massive global warming and worsening air quality. The Triassic was already hot but this might have increased the world's overall temperature by up to 4 degrees and contributed to lowered oxygen and more acidic ocean water as well, albeit nowhere near as bad as at the end of the Permian.    Sea life might have been relatively spared because the oceans could absorb more heat so long as this kind of heating happened on a shorter timeframe before things got really bad, unlike the Permian. Meanwhile on land, the vulcanism was happening in a huge area around the tropics on an already hot planet. Plants took a hit in abundance but came back much quicker compared to the long malaise in the aftermath of the Permian extinction. The biggest victims were the Pseudosuchians and more basal archosaurs, all Phytosaurs, Aetosaurs, Poposaurs, Rauisuchians, Silesaurs, and just about every other miscellaneous groups of archosaurs were dead. Additionally, Drepanosaurs, Tanystropheids, Allokotosaurs, Traversodontids, Titanopterans, Procolophonids, the vast majority of Temnospondyls and the venerable Dicynodonts were also wiped out. Confusingly, the Dinosaurs seemed to come out of this catastrophe almost scot free, most of the major groups at the end of the Triassic carried over into the Jurassic, Theropods and Sauropodomorphs, along with whatever ghostly animal was representing Ornithischians at this point. Dinosaur survival is hard to explain, especially since it can't have been dumb luck when so many survived, its extra confusing because, unlike most mass extinctions, some very large Sauropodomorphs made their way to the Jurassic, animals conceivably weighing several tons. This is extremely unlikely in a mass extinction, where overwhelmingly its the smallest animals that get through to the other side, even during the Permian Lystrosaurus was only about the size of a pig. Its hard to know what the secret sauce was for dinos, their diversity of forms and lifestyles helped, but one big reasons I've seen suggested is that their higher metabolism caused them to monopolize higher latitude environments with bigger temperature swings than the tropics. We've seen that the likes of Plateosaurus were much more common in more temperate regions compared to the baking heat of equatorial Pangaea. The other Archosaurs might have had less flexibility in this regard and were dependent on places with more constant temperatures, so if the tropics became nearly uninhabitable it was harder for them to move north or south when these areas would still have considerable climatic variation over the year with seasons. Dinosaurs were much better placed to handle this, allowing high latitude environments to operate as refugia for them with their insulting feathers and warm blood while the Pseudosuchians were essentially trapped and scorched to death. The other big survivors are multiple lines of Cynodonts, including mammaliaforms (also warm blooded interestingly), Pterosaurs (also also warm blooded), the only surviving Pseudosuchians in the form of Crocodylomorphs, Lepidosaurs, Turtles and Lissamphibians. All of these animals would quickly radiate post extinction to refill the ecosystems over the Jurassic.   Thus the Triassic ended, and all the weirdness we known and love gave way to the more familiar era of true domination by the dinosaurs. With almost all of their competitors taken out Dinosaurs were given essentially free rein to take over the earth, dominating almost every niche in the world for 150+ million years with the exception of the very small ones. They'd grow to be absolute giants, taking on a dizzying variety of forms, and some even learned to fly and withstand the next big hiccup. In the meantime, Crocodylomorphs would go on to refill a number of niches that the older Pseudosuchians previously occupied, most notably the Phytosaurs, but the late Mesozoic in particular would see a lot of novel and unusual crocodilians start to take over some of the niches of their long extinct relatives even in the face of the dinosaurs, especially in places like South America and Madagascar. All the while, the Synapsids, scurrying in the undergrowth, rejecting the pomp of the archosaurs, comfortably taking over small humble niches as undergrowth insectivores and herbivores, and sometimes more, but waiting... planning for a day when they'd get another chance to take the world back from these upstart Archosaurs.   Of course, while I'm done with the story of the Triassic as it relates to land life, there's a lot more to cover, with the incredible story of how the seas went through a dramatic revolution over the course of the Triassic, with the rise of the some of the largest animals in the history of the earth. I hope everybody looks forward to it next week! 
khwarezm fucked around with this message at 19:13 on May 15, 2024 |
|
#
?
May 13, 2024 19:26
|
|
|
Neat
|
|
#
?
May 14, 2024 10:22
|
|
|
|
|
#
?
May 14, 2024 14:56
|
|
|
i like how in a decent proportion of the pics the artist is like "gently caress it i'm gonna have the little one riding on the big one"
|
|
#
?
May 14, 2024 15:30
|
|
|
i should grow ginko trees
|
|
#
?
May 14, 2024 15:37
|
|
|
Yeah these write ups are great! Thanks for putting so much effort in.
|
|
#
?
May 14, 2024 16:23
|
|
|
https://youtu.be/geU1xBaxFGw?si=Pozg3BSxgLa0FFWo
|
|
#
?
May 15, 2024 01:36
|
|
|
|
|
#
?
May 15, 2024 18:18
|
|
|
Definitely real and accurate. https://www.youtube.com/watch?v=XcBoY_aEVj8
|
|
#
?
May 16, 2024 03:34
|
|
|
Ratios and Tendency posted:Definitely real and accurate. Those birds are hosed up
|
|
#
?
May 16, 2024 03:50
|
|
|
Ratios and Tendency posted:Definitely real and accurate. https://i.imgur.com/PdkUx6f.mp4 unmute
|
|
#
?
May 16, 2024 04:40
|
|
|
 pterosaur
|
|
#
?
May 17, 2024 08:55
|
|
|
Regular Wario posted:
That's neat, I thought somebody was having a laugh making a fake looking addition to a duck's beak to make it look prehistoric, until I did a reverse image search.
|
|
#
?
May 17, 2024 16:59
|
|
|
Sorry Fellas, no post this week, I might update some of the older posts though, like recently I was made aware of Oncorhynchus rastrosus, the so called 'Saber toothed Salmon' that was recently found to not have its teeth in a saber tooth position and instead they were horizontal. Absurdly large as well, coming in on the dimensions of a bottlenose Dolphin at 200 kilos and up to 2.5 meters. I may add this to the Miocene oceans post. Also, check out this incredibly freaky looking art work from Hodari Nundu of one in the process of rotting alive like happens to living salmon when they have completed their spawning cycle (word to wise, for people who aren't already familiar with this hosed up phenomenon from not living near spawning areas, do not look up any videos of salmon living out their final week of life after spawning, its incredibly sad and sickening, like they literally turn into zombie fish).  Which reminds me, I probably should go through the art from the last couple of posts and credit the people I got it from.
|
|
#
?
May 20, 2024 01:52
|
|
|
|
| # ? May 29, 2024 23:42 |
|
|
https://www.youtube.com/watch?v=ns0PpRzEsKM I guess AI actually does have some uses.
|
|
#
?
May 28, 2024 02:40
|
|