Am I to believe that this was real?How can a land animal possibly achieve this size?
>>4466838>Am I to believe that this was real?what you believe has no effect on reality>How can a land animal possibly achieve this size?nobody knows
>>4466838>How can a land animal possibly achieve this size?By having better respiratory and skeletal systems than mammals.
>>4466852necessary but not sufficient
By laying eggs, so you're not limited by gestation time.Also having air sacs to make you lighter, like birds have today.
Here go you, faggot op.https://www.youtube.com/results?search_query=how+dinosaurs+big
>>4466838
>>4466863>Also having air sacs to make you lighter, like birds have today.u wot mate?Birds have less dense bone, more like a honeycomb structure, and it's not filled with air They don't have air sacs. Also that only works due to birds' size. Their bone mass isn't sufficient to support dinosaur sizes.
>>4466892I'm not angry at you, just disappointed.
>>4466892Birds have 4-12 extra lungs, generally called air sacs. These extra lungs or air sacs sit next to the neck, spine, chest, hips, legs, wings and tail. The bones they sit next to have tiny holes (foramina, c.f. pneumatic pleurocoels or pulmonary diverticulae) by which air enters the bones. The hollows of the bones are also lined with pulmonary tissue, effectively making the bones into lungs, allowing the bird to breathe through its skeleton. also birds don't inhale and exhale the same way mammals do, air flows in a loop constantly through their bones and lungs. finally they lack the diaphragm used by mammals to breathe, and instead pump air using movements of the legs and hips.these conditions are also found in saurischian dinosaurs, the theropods and sauropods.> Their bone mass isn't sufficient to support dinosaur sizescorrect. Sauropods shouldn't exist based on known biomechanics, just as bumblebees shouldn't fly. But they did, and nobody really knows how.
>>4466895isn't funny how if you mention something someone hasn't heard of, instead of saying "tell me more" or "where did you hear that?" they say "LOL UR A RETARDED LOL RETARD"
>>4466928I think he said>u wot mate?not exactly an insultyou are a retard though.
>>4466838Ask your mom.
>>4466904Maybe they were made of different materialshttps://youtu.be/9cVAVQih_pA
>>4466840>what you believe has no effect on realityWho's reality?
>>4466940Pretty good hypothesis>we find that adult sauropods sat in recliners all day>they asked their children to bring them tons of grass to eat every hour and change the channel on netflix for them>if the young sauropods refused, they slapped them and asked them if they wanted their parents to starve to death>a few mutterings of "after all I did for you" and "kids these days," the young sauropods would go back to cleaning house and serving their parentsreally it's the only model that works
>>4466944>Who's reality?truewho is reality?
>>4466928I think its justified as it was a response to >they dont have sacsif you dont know something dont make statements
>>4466928They guy typed out "birds don't have air sacks" which is embarrassingly incorrect.
>>4466981>if you dont know something dont make statements/an/ would literally disappear in a day
>>4466981>say something stupid>anons correct you>anons mock you for stupidity>leave the thread and pretend you never said stupid thing>next time someone says stupid thing you correct them>also mock them for not knowing thing>pretend like you've always know and were never stupid yourself>maybe even pretend you invented/discovered thing that anon doesn't know>lather>rinse>repeatwhen I first came here nobody knew about avian air sacs. Some of those ignorant fucks are probably itt educating people and acting all superior right now.
>>4466892anon, youre retarded, density is a ratio of mass over volume, birds have denser bones because theyre hollow, they weigh a comparable amount to other animals of a similar sizes while taking up less space, ergo theyre denser
>>4466891Moshops? MOSHOPS! Oh my gosh!Permian synapsid doggie!
>>4468809>birds have denser bones because theyre hollow,based retard denying facts and math and stuff
>>4466838Dunno. Ask your mum.
>>4468854>youre retarded, density is a ratio of mass over volume
have you ever tried it's actually really easy
>>4469226Based kamiya
>>4469227bird bones take up as much space as bones from similar sized animals. The air is on the inside. It counts as part of the volume of the bone.this is how density works in a mixture. Both the bone volume and the air volume count towards the volume of the bone. let me know if you have any questions about this. Don't answer if you're just going to disagree, the rest of the world is ignoring your wrong schizo math because it's not actually useful.
>>4469244except the air doesnt stay trapped in the bones, retard, the hollows are channels for air to move around, you would have a point if it were mammalian bones, but we arent
>>4469249speak for your self human faggot
>>4469249I see you've never examined a bird bone
>>4469249>>4469244>Don't answer if you're just going to disagree, the rest of the world is ignoring your wrong schizo math because it's not actually useful.
>>4466944>Who's reality?Mine
>>4466989>>4466928>>4466895>>4466892/an/ discovers what collective learning is.
>>4469960It's not collective learning if you have one person teaching 80% of the knowledge and getting constantly called a retard for it.If that person stops teaching, the learning stops. Now if some of you actually read up on this stuff on your own, you could take turns teaching. But since most have never heard of it, they have no point at which to start learning. They'd have to read the entire internet to stumble across stuff like that, and nobody does that. Because they're too busy hanging out on /an/ waiting for someone to spoon feed them interesting factoids about animals so they can call that person retarded.
The oxygen in the air was higher before the flood. Read the Bible.
>>4470190dinosaurs lived after the floodremember leviathan
>>44668381) More fertile ecosystems in the Jurassic and Cretaceous due to higher global temperatures and higher atmospheric CO2 - meant lots of food to support large herbivores. There was a period of unprecedented global climate stability between the beginning of the Jurassic and the end of the Cretaceous, with the major shifts being the opening of shallow epicontinental seas with the break up of Pangea, the formation of circum-equatorial warm ocean currents with the creation of the Tethys and Atlantic Oceans, and generally rising sea levels. This allowed for massive, stable, plant-based ecosystems that had very high carrying capacities to dominate the planet and encourage the evolution of truly giant dinosaurs. The Cenozoic, by contast, has seen massive shifts in climate and ecology, with gradual cooling and drying over the last 30 million years or so with ice forming at the poles. Ecosystems seem to generally have been less stable, although this hasn't precluded the evolution of giant land mammals, like the paraceratheriids, giant proboscideans and ground sloths.
>>4470421>>44668382) Evolutionary arms race/positive feedback loop between predatory theropods and other dinosaurs - larger herbivores would survive predation more regularly, leading to generally larger populations, meaning larger predators would do better, meaning prey had to be even larger to survive. Sauropods were one of the first truly successful branches of dinosaur, prosauropods diversified in the Late Triassic and by the Mid Jurassic they were the dominant herbivores in most land ecosystems on earth. This meant they were the main target for predatory theropods, so developed the arms race that led to the giant sauropods and giant carnivores of the Late Jurassic (eg Allosaurus and Diplodocus). Ornithischian herbivores in the Jurassic were lagging behind sauropods and were crowded out of the giant herbivore niches, so either evolved to be faster and more agile or relied on armoured defence (like stegosaurs). After the Cenomanian-Turonian sea level rise there was a faunal turnover in the Mid-Cretaceous, epicontinental seas along the Atlantic and Tethys flooded many of the lowland floodplains the giant Laurasian sauropods relied on for their nesting and feeding grounds, and they saw stricter competition from large ornithischians like giant ceratopsians and hadrosaurs, although sauropods were still very dominant in Gondwana and got even bigger.
>>44704223) The archosaur unidirectional respiration system was incredibly successful, and had evolved in the early days of the Triassic, when atmospheric oxygen was still low after the Pemian-Triassic extinction event (11%). This, along with their agile builds and generally more efficient metabolisms than other reptiles and the synapsids, is what allowed dinosaurs, pterosaurs and crocodilians to advance and spread during the Late Triassic. When atmospheric oxygen rose again in the Jurassic, dinosaurs were primed for developing even better metabolisms to support larger and larger sizes. At certain points in the Jurassic and Cretaceous, O2 density reached upwards of 30%, higher than the present day. Bird lungs are still more efficient than mammal lungs in the Holocene. A giant Apatosaurus could not have taken in enough breath to live if it had a reptilian or mammalian respiratory system, instead it seems most likely that it had an avian-style one. 4) Similarly, saurischian dinosaurs, especially sauropods, had heavily pneumatised skeletons, with air sacs like modern birds buoying up the heavy bones and reducing overall density while maintaining structural support, especially around the vertebrae (which helps hold up everything else). As synapsids, we have pneumatised skulls, for example with our paranasal sinuses, but dinosaurs and birds have extensive postcranial skeletal pneumaticity - they basically have air-filled sinuses throughout their skeletons. This is what also makes birds so light and makes their respiration so efficient. Pterosaurs also had air sacs, but ornithischians didn't, though they still had advanced breathing and relatively high metabolic rates. We can imagine air sacs would lighten the weight of a colossal sauropod or theropod, or the giant pterosaurs.
>>44704245) For the intermediate metabolisms of giant sauropods, large size also provided them with homeothermy, meaning they could better regulate their internal body temperatures (though if they had been completely warm-blooded endotherms like mammals they would have cooked alive).6) Sexual selection is also a potential cause and explanation - if you already have all of these factors pushing you to grow larger and select larger mates, then more and more of your species are going to be bigger and bigger.There are still many biomechanical questions concerning the truly giant sauropods and their musculoskeletal and circulatory systems, but these are some of the reasons why and ways in which dinosaurs got so big.
>>4466838>extra large things are so impressive that they must be impossible?
>>4470425Oh, and sauropod length was simply a balancing act. They evolved very long necks to expand their browsing areas. Depending on the species, they could extend their next to the tops of giant conifers, or have a wide area in which to crop cycads and ferns. This massively long neck needed balancing, and the natural counterweight in dinosaur biomechanics had always been the tail. Suspension bridge.
So did these big dumb fucks have to stay in water all the time to keep the weight off their joints like old human fatties in a water aerobics class?
>>4466838That’s what I thought when I met your fat mother but she still gave me some sloppy.
>>4470529No, they were brilliantly designed for it. Fat women are an abomination against nature; sauropods were not.
>>4470424>At certain points in the Jurassic and Cretaceous, O2 density reached upwards of 30%, higher than the present day.Climatologists count CO2 as atmospheric oxygen. So no. Oxygen being elevated simply means CO2 was elevated, not O2.In the Late Jurassic anyways. I don't know about the Cretaceous, but I've done O2/CO2 surveys in the kimmeridgian and tithonian, and there was almost 30% LESS O2 at those times.coincidentally the same time period when sauropods evolved gigantism as far as we can tell.
>>4466838Tankbros said the giant robots in my Japanese animes wouldn't work because they'd sink into the topsoil from ground pressure. These critters plus pterodactyls with the lopsided massive heads are why I believe Jews buried dinosaur bones to trick Christians. It goes against science.
>>4470764Seems the source for Cretaceous numbers I was using is outdated, my apologies. But if you look back at what I was saying, my point wasn't that higher O2 = gigantism, in fact nothing of the sort, but rather the very low oxygen at the start of the Triassic (c.12% immediately post mass extinction) encouraged the evolution of unidirectional respiration in archosaurs as a survival mechanism. Then, when oxygen levels rose back to the 15%-20% range as the Triassic went on it meant that this unidirectional respiration allowed them more sophisticated metabolisms that could support larger bodies and more active lifestyles. Based on these graphs, the next step would be to posit that the drop in O2 during Triassic-Jurassic extinction event placed even more selection pressures on early dinosaurs and pterosaurs, leading to them refining their unidirectional respiratory systems even further, possibly by evolving postcranial pneumatised skeletons? This would make large dinosaurs highly efficient breathers with adaptive metabolisms (maybe this is when their mesothermy also developed), meaning they could cope with fluctuating oxygen content. I wasn't arguing that more oxygen = bigger, but that low oxygen meant that specialised breathing was required, and then a subsequent boost in oxygen saw that specialised breathing flourish further, then be put under more pressure, then flourish again.
>>4470764>>4470962>Climatologists count CO2 as atmospheric oxygen. No they don't. I mean, that claim seems pretty irrelevant anyway, since CO2 has, at least since the Cambrian, been a negligible percentage of the atmosphere. Oxygen is currently 21% of the atmosphere in dry air, while CO2 is 0.04%. In the Cambrian, when CO2 was probably at its highest since the start of the Phanerozoic, it was still only around 0.4%, at a push 0.6%, while oxygen generally oscillated between 15-20%. Between the Late Triassic and Early Jurassic, CO2 peaked at 0.2% (2000 ppm). So whether you count CO2 as atmospheric oxygen or not, it really means no difference to the actual oxygen content and what we can learn from those numbers. Obviously even a tiny 0.01% increase in CO2 can quickly effect the climate, as it is a greenhouse gas, but that's not the same as oxygen levels. The two are linked, sure, but measuring CO2 and bulking it in with O2 would increase O2 measurements by, like, less than 1% in every case for the last 600 million years, so I don't really know what you're talking about.>Oxygen being elevated simply means CO2 was elevated, not O2.No. Like I said, CO2 makes up barely any of the atmosphere, no matter what time period you're at in the Phanerozoic. Oxygen being elevated means that oxygen is elevated.>30% LESS O2 at those times30% less than what?
>>4470747Damn that one has a fat neck. Reminds me of your mom
>>4470764>So no. Oxygen being elevated simply means CO2 was elevated, not O2.this is nonsense
>>4470964Synapsids had tidal lungs which, like modern mammals, rely on diaphragmatic inhalation and exhalation. Birds and crocodilians, and thus most likely dinosaurs, pterosaurs and other archosaurs, can basically breathe in and out at the same time, as oxygen-rich air is blown through their lungs both when they inhale and when they exhale. This is probably a reaction to low oxygen in the post-extinction Early Triassic.Erect limbs also helped archosaurs avoid Carrier's constraint, where side to side crawling squishes your lungs, meaning their breathing was again more efficient than other diapsids or the synapsids, many of which were still sprawling. However, archosaurs had already started becoming 'ruling reptiles' while still sprawling, so this was probably a secondary proliferation rather than an initial cause.Uric acid in diapsids was also more efficient in the arid parts Pangea than synapsid urine, although there were definitely synapsids that were well adapted to the arid environments. It seems the biggest thing that kept cynodonts small by the end of the Triassic was actually competition within the cynodont groups themselves, as they all occupied fairly similar niches in a supercontinent Earth with very little bio-provincialism.They had also evolved the four-chambered hearts with pulmonary bypasses (meaning they can work with three chambers underwater) that are present in modern birds and mammals. Other diapsids lacked this, giving archosaurs the edge.Dinosaurs and pterosaurs advanced all of these great archosaur innovations even further, and, after the Triassic–Jurassic extinction, they came out doing very well for themselves. Pterosaurs obviously had a golden ticket being the first volant vertebrates in the history of the Earth.
>>4470980>They had also evolved the four-chambered heartsAs in, archosaurs had. If dinosaurs were indeed mostly 'mesothermic', while early archosaurs were cold blooded like modern crocodiles, then they seem to have achieved some standard of homeothermy in half the time it took synapsids.In many ways, mammals really just lucked out with the K-Pg extinction, as well as the cooling of the planet over the last 33 million years since the end-Eocene extinction. While they were flourishing during the warm period of the Paleocene and Eocene, their excellent homeothermic metabolisms and temperature regulation, as well as their thermal insulation in the form of fur, meant they were well prepared for the Late Cenozoic cooling process. The nocturnal bottleneck (caused by many mammal lineages being nocturnal during the Mesozoic) lent them generally excellent sensory equipment - hearing, smell and touch, although most mammals have worse vision than birds and reptiles. They also have a unique type of brown adipose tissue, which allowed them to maintain high body temperatures in cold nights. This is also the root of our circadian rhythms and tachymetabolisms. Therapsids already had differentiated, precisely occluded teeth, but the need for a varied omnivorous or insectivorous diet in early therian mammals saw even more variety in their dentition. The tradeoff for having night ancestors is we lack ocular shielding, gladusol sun-defense, and sun-reliant photolyase DNA repair.
>>4470988We also have pretty unique and adaptable guts with microbiomes, which most other vertebrates don't have, probably thanks to specialised eaters in our ancestry. Obviously lactation and mammary glands, ancestral to most synapsids it seems, was a huge win as well. And, while the marsupial gestation method of constantly nurturing altricial young in a pouch is very successful, it was the placental method of internally nurturing young during gestation until they reach precociality as the moment of birth that gave the eutherians the absolute edge in most of the world over the course of the Cenozoic.Of course, there is also brain size, which didn't really start to catch up with body size til the Eocene.However, when it comes to breathing, our two biggest innovations are respiratory turbinates covered in mucous in the nasal cavity that warm and moisten inhaled air and extract heat and moisture from exhaled air, meaning we can breath quickly without drying our lungs out, and our diaphragms, which can be seen as early as the the caseid synapsids. We didn't evolve unidirectional breathing, but archosaurs did, giving them the edge in the Triassic and leading dinosaurs and pterosaurs to dominate for 130+ million years. Personally I think archosaur breathing is more impressive than mammal breathing, and advanced archosaur breathing is what has allowed birds to become the best vertebrate flyers of all time, dominating most aerial ecosystems and being the most numerous and diverse group of tetrapods, with 10,000 species currently recognised, almost twice the species diversity of mammals. So archosaurs aren't doing too bad. Non-avian dinosaurs simply lost the game of luck.
>>4470962>>4470989https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7017431/This is a nice succinct paper that summarises the hypothetical relationship between Early Triassic hypoxia and the evolution of the unidirectional parabronchial lungs, although it makes it quite clear that this is a very theoretical stage and actual analysis of faunal turnover in the Triassic is needed to see just how quickly the 'ruling reptiles' proliferated. I would posit a soft version of this theory, where unidirectional breathing is just one arrow in the archosaur quiver that allowed them to prosper over the course of the Triassic, and it took the innovations of the avemetatarsalians in the Late Triassic and the culling of the T-J extinction for things to really kick off.The evolution of postcranial pneumaticity in pterosaurs and dinosaurs is really the crux. Sauropods would have needed an excellent and efficient archosaurian breathing system to respire adequately, but they would also have required heavily pneumatised bones (which evolved out of unidirectional respiration) to lift their giant bodies. Which was the original point.
>>4470999Oh and they also mention the blood-gas barrier in birds which I forgot about, though I have a feeling that's a product of being LEET flyers and terrestrial dinosaurs wouldn't have needed such a MAXXED system
>>4470999>heavily pneumatised bones (which evolved out of unidirectional respiration)Got any reading material on that?
>>4470962Postcranial pneumaticity was common and extensive when sauropods first appear in the record. Since it's shared by theropods, it's reasonable to assume it evolved very shortly after the first dinosaurs.Probably weirder is that it continued to expand as oxygen levels rose.>>4470964>No they don't.sure we do. CO2 is mostly oxygen. It countsthe part you're seeming to miss is that even though CO2 is a tiny fraction of air, if you increase it animals quickly begin to suffocate.It's hard to strip CO2 from hemoglobin when the air has more CO2 in it.>30% less than what?30% less than now. The difference was converted to CO2>>4470966>this is nonsenseI posted you a graph. Show me that you understand it and then tell me what you think is wrong with it.when total O2 rises, CO2 then rises and absorbs it.
>>4470999The problem is that both pterosaurs and saurischians had pneumatic pleurocoels, while ornithischians didn'tAlso pterosaurs, ornithischians, and theropods are known to have feathers or fuzz while sauropods didn't.meaning one or both of these traits either evolved convergently or were convergently lost.
>>4470989>our two biggest innovations are respiratory turbinatesalso found in dinosaurs and birds
>>4471007When I talk about pneumatised bones/skeleton I specifically mean the PSP air sac system>This raises the possibility that unidirectional airflow evolved prior to the pseudosuchian/avemetatarsalian split and was inherited by all archosaurs [18], [111], [112]. The ancestral archosaur has also previously been proposed to have possessed a multi-chambered lung with partial separation of the pump and exchanger [7], [18]. As discussed above, we hypothesize that a non-exchange air sac system is plesiomorphic for (and homologous across) Ornithodira. The split of pseudosuchian and avemetatarsalian (including Ornithodira) lineages occurred before the end of the Early Triassic [48], [66], [67].>A plausible hypothesis, therefore, is that as proposed previously [18] the ancestral archosaur possessed lungs with unidirectional airflow and incomplete separation of the pump and exchanger (but with regions of low parenchymal density that could form the precursors of air sacs), but lacked the true air sac system of ornithodirans (with a complete separation between pump and exchanger), and that the latter evolved in concert with locomotor and other changes in the earliest avemetatarsalians during the Early to early Middle Triassic (Fig. 1). This hypothesis would be consistent with recent work suggesting that elevated evolutionary rates occurred during the earliest phase of archosaur evolution [118]. Furthermore, this hypothesis would suggest that more efficient lung ventilation initially evolved in concert with increased activity levels and (possibly) heightened metabolic rates; subsequently PSP originated and was elaborated on in multiple ornithodiran lineages independently, particularly in large-bodied and/or flying taxa [8], [11], [12].https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0034094#s4>Reassessment of the Evidence for Postcranial Skeletal Pneumaticity in Triassic Archosaurs, and the Early Evolution of the Avian Respiratory System
>>4471058I tend to agree with that idea,but would caution that we don't even know for a fact if dinosaurs possessed avian type air sacs and non-septate lungs because those don't fossilize.I think the presence of pleuorcoels is strong evidence, but it's certainly not proof or anything.
>>4471058also this would mean ornithischians lost the avian condition and re-evolved the earlier septate lungthis is a violation of Dollolosing feathers and regaining scales is hard enough. Losing one type of lung and going back to another is probably impossible.
>>4471058>>4471065>also this would mean ornithischians lost the avian condition and re-evolved the earlier septate lungor that ornithischians aren't dinosaurs, which is generally rejected by everyone that studies dinosaurs because it would require a shitload more really wierd convergence.
>>4471047>CO2 is mostly oxygen. It countsIn every atmospheric makeup I've seen its working with O2 as oxygen molecules, not oxygen in other compounds. Otherwise water vapour would count, and oxygen content would be even higher. It would also be useless ecologically speaking, because aerobes can breathe oxygen, they can't breath CO2 or water vapour. The distinction is necessary.>the part you're seeming to miss is that even though CO2 is a tiny fraction of air, if you increase it animals quickly begin to suffocate.Yeah I get that, that's not my point. Your initial claim, that oxygen levels elevating 'simply means CO2 was elevated, not O2' is just not true. O2 climbing in the Carboniferous is O2 climbing. The percentage of any given O2 that is CO2, if you're including that, is miniscule.>30% less than now.Right I was confused, so you mean at like 15%>Show me that you understand it and then tell me what you think is wrong with it.Nothing's wrong with the graph, it's different from an older graph I saw that saw O2 climbing more steadily throughout the Late Jurassic and Early Cretaceous, obviously that's either outdated or an opposing model.
>>4471047>>4471073>when total O2 rises, CO2 then rises and absorbs it.I know that, that wasn't your initial point. Your initial point was1) O2 wasn't high in the Jurassic. I already conceded this and it wasn't part of my original point anyway.2) Measured O2 variations are actually just a product of CO2 variations, which isn't true. CarboxylateTell me that you understand this graph that I've posted here >>4470964 that shows that CO2 levels are neither a perfect reflection of O2 levels, and that they don't constitute the reason for the major shifts in O2 levels. CO2 levels are subject to other factors, like decomposition, mineral dissolution and ocean release, whereas most O2 comes from photosynthesising green plants or cyanobacteria. If there is any correlation, it's a negative correlation as in your graph - the greater O2 content, the less CO2 content and the greater the carbon capture, as in the Carboniferous Lepidodendron forests. So your statement that>Oxygen being elevated simply means CO2 was elevatedIs actually a positive correlation when it should be negative. It should be>Oxygen being elevated might generally mean CO2 was depleted and more carbon was captured in the biosphere/geosphere/pedosphere etc.
>>4471073>Otherwise water vapour would count, and oxygen content would be even higher.yes. It does and is>It would also be useless ecologically speaking, because aerobes can breathe oxygen, they can't breath CO2 or water vapour. The distinction is necessary.Also correct. climatologists don't usually measure oxygen for ecological studies. We're usually looking at geology.so you have to be careful reading oxygen graphs, because they may not be relevant to life on earth. Or have the opposite relevance, e.g. extremely elevated CO2 will appear on a geo study as high O. But it's extremely toxic to life on earth. Not toxic directly of course, but as an asphyxiant and acid.
>>4471076>most O2 comes from photosynthesising green plants or cyanobacteriadepends on the point in time.
>>4471076>>Oxygen being elevated might generally mean CO2 was depleted and more carbon was captured in the biosphere/geosphere/pedosphere etc.yes, this is generally correct.but as oxygen elevates, CO2 follows. So any net increase in atmospheric TOTAL oxygen is going to convert to CO2 over time.
>>4471076>most O2 comes from photosynthesising green plants or cyanobacteria.this is a confusion between geology and ecology.plants don't actually produce oxygen, that's impossible. They break down molecules containing oxygen and then release it.so when a geologist says oxygen is elevated, we don't necessarily mean O2. We mean total oxygen. Which doesn't come from plants or bacteria. It comes from volcanos and erosion.similarly when oxygen drops, it's because it's being absorbed into rocks, primarily as CO2 in marine sediments but also as biomass being buried in sediments or by the oxidation of eroding rock materials.
>>4471083Because of this it's quite possible for total oxygen to be elevated but O2 to be reduced. Usually by conversion of excess O2 to CO2
>>4471051Convergent loss of integument isn't that crazy to me. Partial quill/pycnofibre/protofeather integument seems to be ancestral for ornithodirans and then was lost in big dinosaurs for obvious reasons. The air sacs is another question. Until we find more evidence, I feel like the most likely answer is that it evolved independently in pterosaurs and saurischians, but that the unidirectional respiratory system is somehow, morphologically, a good springboard for the evolution of pneumatic pleurocoels. Like unidirectional breathing provides the right building blocks for the evolution of the air sacs, so they became prevalent in both pterosaurs and saurischians. Also was probably a necessary adaptation for each ecological niche.>>4471063>I think the presence of pleuorcoels is strong evidence, but it's certainly not proof or anything.Yeah course not, I'm just hypothesising. Trying to create a convincing evolutionary argument. I always get caught in the trap of telling just-so parables though, because I'm an amateur and a STORYTELLER.>>4471065Yeah I agree. So, unless pterosaurs are actually saurischians, or ornithischians aren't dinosaurs (unlikely like you said), the pleurocoels were involved independently in both pterosaurs and saurischians.>>4471055>also found in dinosaurs and birdsYeah they convergently evolved the respiratory turbinates from the ancestral olfactory turbinates. So even one of our special things they have as well. Damn archosaurs.
>>4471088Personally I see evolution or loss of fibers as a lot easier than avian type airways. In particular I don't think it's possible for avian lungs to be ancestral to all dinosaurs and then lost in one group. That strikes me as probably impossible.
>>4471078>climatologists don't usually measure oxygen for ecological studies.Ok, so I see the discrepancy. I was discussing a theoretical oxygen makeup and its paleoecological impact in the Early Triassic, which like I've said is a shaky theory that needs a full analysis of faunal turnover to actually back. Like I said, I'm hypothesising based on what I've read in papers. Geologically obviously you're talking in a different ballpark, so we're at cross purposes.>so you have to be careful reading oxygen graphs, because they may not be relevant to life on earth. Or have the opposite relevance, e.g. extremely elevated CO2 will appear on a geo study as high O. But it's extremely toxic to life on earth. Not toxic directly of course, but as an asphyxiant and acid.I understand>>4471079>depends on the point in time.Of course>>4471081>>4471083>>4471085Ok, I gotcha. I guess I just don't really see the point in not differentiating actual free O2 as a molecule that can be used by terrestrial breathing tetrapods from the poisonous CO2.>Because of this it's quite possible for total oxygen to be elevated but O2 to be reduced. I understand, but surely you're referring to the totality of oxygen, including non-atmospheric? I specifically mean the breathable oxygen in the atmosphere at a given time that we can try and surmise the ecological effects of, in particular because of our discussion about archosaur breathing and sauropod size.You could still concede the original thing, that if a rise in atmospheric CO2 is tallied into the atmospheric O2 level, it would generally contribute very little to atmospheric O2 levels. That CO2 has a large ecological effect, but numbers-wise it's very small, which is why I was initially confused.
>>4471095>Personally I see evolution or loss of fibers as a lot easier than avian type airways. In particular I don't think it's possible for avian lungs to be ancestral to all dinosaurs and then lost in one group. That strikes me as probably impossible.Yeah I 1000% agree. I think it's probably a pterosaur-saurischian convergence. It seems likely based on some research I've been reading that both lineages were more able to evolve postcranial skeletal pneumaticity due in some part to the preexisting benefits of their unidirectional parabronchial lungs.
>>4471099>I guess I just don't really see the point in not differentiating actual free O2 as a molecule that can be used by terrestrial breathing tetrapods from the poisonous CO2.It tells us how much feedstock is available for biomass, and how quickly they're converting it back into rocks.it gives us info on the chemical composition of mountain ranges that eroded millions of years ago, and volcanos that erupted long before now.and it tells us a bit about the history of the planet, solar system, and universe.>surely you're referring to the totality of oxygen, including non-atmospheric? nah, it's atmospheric, but it includes compounds of oxygen that animals and often plants can't consume.>it would generally contribute very little to atmospheric O2 levelsthe graph I posted shows what I'm talking about. Part of the dynamic is the carbon cycle removing oxygen from the air. So even if the conversion isn't direct, it's still there. When O2 goes down, CO2 goes up. And the opposite.As you say, none of this is directly relevant to any single organism on the planet. That's why I urge caution interpreting oxygen graphs to ecology if they're taken from geological data.Paleontologists are geologists, so we understand this difference in purpose and can adjust numbers to make them relevant to plants or animals or whatever.
>>4471102yes, either way both lineages had a predisposition for evolving feathers/avian lungs. cranial pneumaticity is extremely common, we have it. But pulmonary invasion of sinuses is pretty weird.
>>4471105>It tells us how much feedstock is available for biomass, and how quickly they're converting it back into rocks.>it gives us info on the chemical composition of mountain ranges that eroded millions of years ago, and volcanos that erupted long before now.>and it tells us a bit about the history of the planet, solar system, and universe.No I know in general, and that's genuinely fascinating, I just mean specifically with regards to what we were talking about (hypoxia in Early Triassic potentially leading to archosaur breathing innovations). Feedstock for biomass is also obviously relevant to dinosaur size as well.>nah, it's atmospheric, but it includes compounds of oxygen that animals and often plants can't consume.Ok, again, obviously that has extensive ecological effects, but when we're talking about hypoxia in the Early Triassic as a selection pressure for more efficient respiration in diapsids, we're talking about the oxygen that animals can consume, eg O2.>Part of the dynamic is the carbon cycle removing oxygen from the air. So even if the conversion isn't direct, it's still there. When O2 goes down, CO2 goes up. And the opposite.Yeah I know, nice
>>4471113>>4471105>As you say, none of this is directly relevant to any single organism on the planet. That's why I urge caution interpreting oxygen graphs to ecology if they're taken from geological data.>Paleontologists are geologists, so we understand this difference in purpose and can adjust numbers to make them relevant to plants or animals or whatever.Right. But would you say that the geological data on overall oxygen content in the very Early Triassic and its apparent drop from the Late Permian (part of the P-Tr extinction) can, when adjusted for relevance as you say, inform us about certain environmental pressures that Pangaean diapsids would have been experiencing at the time? The only problem is this is primarily a thought experiment for me and for you as well, because there hasn't yet been a comprehensive survey into the faunal changeover of the Mid-Triassic to see if the evolutionary traits of archosaurs and their apparent success did in some way reflect these ecological conditions that we could infer from the geological data.
>>4471113>hypoxia in Early Triassic potentially leading to archosaur breathing innovationsI wasn't disputing that. I doubt it happened that early, but the mechanism makes sense whenever it happened.avian lungs are pretty obviously an adaptation to high activity in a low oxygen environments.
>>4471114that would depend on how athletic those archosaurs are. And whether or not they were warm blooded.a hummingbird consumes oxygen much faster than an alligator.
>>4471108Yeah archosaurs are amazing! even the shit ones
>>4466891keked
>>4471118>even the shit onesjejwhich ones are those?
>>4471115>that would depend on how athletic those archosaurs are. And whether or not they were warm blooded.Think the consensus is the early ones weren't warm blooded but probably still pretty active for diapsid standards, again not sure.>I wasn't disputing that. I doubt it happened that early, but the mechanism makes sense whenever it happened.>avian lungs are pretty obviously an adaptation to high activity in a low oxygen environments.Ok, I guess the question is if that adaptation goes back to early archosaurs, and the more efficient avian version (as opposed to the alligator's) is an ornithodiran thing. But we don't know right now.>I wasn't disputing that. Well, I guess that was the main thrust of that part of my point, so I'm happy. Also thanks for the geology insights.
>>4471121
>>4471123>the consensus is the early ones weren't warm blooded but probably still pretty active for diapsid standards, again not sure.I'm also not sure. Not really my area of study. All I've read is speculation based on the crocodilian patent foramen panizza.>>4471126ah, I like those guys. Their brains are phenomenal, even for birds
>>4471123>I guess that was the main thrust of that part of my point, so I'm happy.Yeah, I wasn't disagreeing with that.just the part about O2 being 30% higher at times in the Jurassic. And the part where people call me a retard for pointing out the truth.
>>4471128>All I've read is speculation based on the crocodilian patent foramen panizza.Yeah same, but then there's also the 4-chambers. In my mind they began evolving mesothermy alongside the unidirectional parabronchial lungs.>>4471128>Their brains are phenomenal, even for birdslove those little shitheads
>>4471131>just the part about O2 being 30% higher at times in the Jurassic.My mistake, thank you for correcting me. >And the part where people call me a retard for pointing out the truth.I didnt say that! this is my first post >>4470421
>>4471140No worries. I have a bit of time so I'm going to go back and hit a couple valid points you mentioned.CO2 is a tiny fraction of the atmosphere, but O2 isn't exactly huge either. It's less than a quarter of air now and was as low as 13% in the kimmeridgian. So increasing CO2 by 10x or more still represents hundreds of millions of tons of oxygen in the air.The reason water vapor and carbonic acid or sulfuric acid isn't given as much weight is the same reason climatologists often ignore it now-It flows through the air very quickly. Millions of tons of oxygen pass into and out of the air every day in the form of water. And while that is a geological process, it is usually more useful to find an average and ignore the massive fluctuations vs. things like O2 and CO2. But in the Jurassic the climate was monsoonal with 2 seasons, the rainy season and the dry season. So water vapor constituted perhaps billions of tons of oxygen in the air, but that evened out over the seasons to some average number.Other sources like ozone, sulfur dioxide, various acids, carbon monoxide, etc. were much smaller, but still significant to total oxygen.I discuss all these because most oxygen graphs DO SHOW ELEVATED OXYGEN in the Jurassic despite breathable O2 being extremely low at the time. I assumed you were looking at one of these graphs. As you may have been.
>>4471140Regarding the effects on animal life, a couple thoughts:1. Low O2 and high CO2 was probably a force keeping mammals small at the time. Other forces existed, but the fact is humans couldn't function well in Jurassic air, and the risk of dying would be much higher for us if we lived then. Simply put, the oxygen levels were low enough to kill large mammals. Somehow dinosaurs not only survived this, but became enormous.2. Avian lungs could've evolved in the early triassic, but the atmosphere was poor enough in the jurassic they could've evolved then as well.3. Probably the biggest problem with any explanation is one ornithologists would immediately spot:Birds have amazingly efficient lungs, but that also means they die much faster when exposed to elevated toxins and asphyxiants. Whether it's burnt teflon from nonstick pans or methane in coal mines, or carbon monoxide from a furnace, birds die much faster than mammals from bad air.so there's a huge question of how dinosaurs would manage to survive essentially poisonous air that lasted millions of years if they had bird lungs.The last one is an unsolved problem in paleontology, and a reason why lots of scientists doubt that dinosaurs actually had avian style lungs.
>>4471286>so there's a huge question of how dinosaurs would manage to survive essentially poisonous air that lasted millions of years if they had bird lungs.though as a counterargument, birds had certainly evolved by that time, and they managed to survive it just fine. So either the air wasn't that toxic, or birds were less prone to death by gasses at that time. Though why they'd be more robust back then is unknown.
>>4471287>why they'd be more robust back then is unknown.size may have been the important factor. Most pet birds now are much smaller than the average Jurassic bird probably was, meaning much faster respiration and thus perhaps higher sensitivity to toxins in the air.there's also the question of climate and metabolism, since the planet was much warmer then it's possible that metabolism was slower without the extreme needs for active endothermy that modern birds have.
>>4471291these however are unanswerable questions, just as we don't actually know what the lungs of Jurassic birds were like.
>>4471140The bigger problem is one you already noted ittall these are reasons WHY sauropods could become enormous, but ignore HOW they became enormous.Basically problems like how the bones supported their weight, or how their hearts pumped blood to great heights, or how they mated, are unanswered questions in paleontology, and perhaps more what OP was asking about.
>>4466838>How can a land animal possibly achieve this size?>I need to eat everything to grow large>neck goes BRRRRRRRRR
>>4466838roids
>>4471302>bones supported their weighttheir legs were built like elephants, they were almost ungulates>how their hearts pumped blood to great heightsa lot them did not eat from the tops of trees, most of them were lawnmowers, and the ones that did have height probably we like giraffes, big heart and a bunch of other things>how they mated,they probably just turned around, like stegosaurus or anyklosaurus where mounting is very difficult>are unanswered questions in paleontologybecause these questions are based on soft tissues, things that dont really preserve, so all you can do is guess and never really get a definitive answer unless you build a time machine and vivisect one
>>4471283>But in the Jurassic the climate was monsoonal with 2 seasons, the rainy season and the dry season. So water vapor constituted perhaps billions of tons of oxygen in the air, but that evened out over the seasons to some average number.That was probably the source of my inaccurate information>I discuss all these because most oxygen graphs DO SHOW ELEVATED OXYGEN in the Jurassic despite breathable O2 being extremely low at the time. I assumed you were looking at one of these graphs. As you may have been.Now I understand, thanks>>4471286>1. Low O2 and high CO2 was probably a force keeping mammals small at the time. Other forces existed, but the fact is humans couldn't function well in Jurassic air, and the risk of dying would be much higher for us if we lived then. Simply put, the oxygen levels were low enough to kill large mammals. Somehow dinosaurs not only survived this, but became enormous.Yeah, and that was also true for the early Triassic (at least wrt low O2), so ONE theory I've seen in some places was this is what led to more efficient breathing in archosaurs. We know both crocodilians and birds have unidirectional breathing, but crocodiles don't have the post-cranial skeletal pneumaticity of birds. Unless crocodilians and birds evolved them independently, the assumption amongst some paleobiologists is that unidirectional breathing is synapomorphic for archosaurs, and in fact every lineage of avemetatarsalians and pseudosuchians had this type of breathing, while only some lineages of avemetatarsalians (saurischians and pterosaurs) evolved the more derived post-cranial skeletal pneumaticity that we know in birds, which appears to be a derived trait seen only in saurischians and pterosaurs, although again we don't know for certain with non-avian saurischians and pterosaurs, because we only have fossil remains.
>>4471286The next step, as we discussed, is explaining why ornithischians don't seem to have pneumatised skeletons, and what their breathing apparatus was. I read this quite recent paper about the ventilatory anatomy of Hypsilophodon that suggests ornithischians evolved a unique lung arrangement that was still unidirectional but relied on what the authors call 'pelvic bellows':https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8260226/And there's also this article that describes unidirectional airflow in iguanas, which might imply that it's a synapomorphy in all diapsids:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4260542/>2. Avian lungs could've evolved in the early triassic, but the atmosphere was poor enough in the jurassic they could've evolved then as well.That's a good point, I don't necessarily mean avian lungs alone though (as in a ventilation system with post-cranial skeletal pneumaticity as seen in birds and theorised for saurischians and pterosaurs), but rather the pre-avian unidirectional breathing method that seems to be basal for other archosaurs as well (crocodilians). Though, if it's possible that it's basal for all diapsids (as iguana paper suggest), that might also scuttle any Triassic O2 theory. Again, I don't think that post-cranial skeletal pneumaticity is definitely a Triassic development, but if we argue that PSP in theropods (birds, Aerosteon) and sauropods is a synapomorphy, and that the pneumatic airspaces in sauropod vertebrae have a similar function and origin as the airspaces in birds, then that would imply that it predates the theropod-sauropod split, which is usually thought to have happened in the Late Triassic, probably Carnian. But anyway, that's pneumatism, which isn't the same as unidirectional breathing alone, but just a potential derived form of it, at least according to my understanding.
>>4471710>Based on the presence or absence of postcranial pneumaticity and an array of vertebral laminae and fossae, Butler, Barrett & Gower (2012) proposed that pulmonary air sacs were present in the common ancestor of Ornithodira and were subsequently lost in ornithischian and other members of the clade. Benson et al. (2011) concluded that pneumatization in non-volant maniraptoran nonavian theropods evolved in association with an elevated metabolic rate and “high-performance” endothermy. Wedel (2007) and Wedel (2009) concluded that air sac-driven pulmonary ventilation was ancestral for Saurischia based on the presence of vertebral pneumaticity in various sauropods and theropods.This is from this paper: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3628916/I don't really buy Barrett and Gower's proposition that pulmonary air sacs are ancestral for ornithodira and lost in ornithischians, because of Dollo's law like you said, but I can see that they might have been ancestral for saurischians.>Here we have shown that Nile crocodiles neither have postcranial pneumaticity nor air sacs and yet have lungs with truly flow-through ventilation. Hence unidirectional ventilatory flow (a flow-through lung in physiological terms) is possible in an ectothermic animal without pneumaticity and without air sacs. This emphasizes that bronchial anatomy, air sac anatomy, and ventilatory patterns can be decoupled from each other in archosaurs and should not be presumed to be correlated in simple ways.So the parabronchial unidirectional breathing is not the same as the derived pulmonary sac system and the pneumaticity.
>>4471712>>4471286>Birds have amazingly efficient lungs, but that also means they die much faster when exposed to elevated toxins and asphyxiants. Whether it's burnt teflon from nonstick pans or methane in coal mines, or carbon monoxide from a furnace, birds die much faster than mammals from bad air.That's true, so maybe the blood-gas barrier was thicker in Jurassic saurischians, as it appears to be in crocodilians. Again, bird lungs are different from other archosaur lungs because of their pulmonary sacs, my argument wasn't that archosaurs evolved pulmonary sacs very early on, but rather that they evolved unidirectional breathing. Pulmonary sacs and PSP seem to have been an avemetatarsalian innovation.>The last one is an unsolved problem in paleontology, and a reason why lots of scientists doubt that dinosaurs actually had avian style lungs.Yeah. My intuition tells me they could've have had a set of transitional forms that were not yet as efficient as those of birds, but still allowed for greater and more efficient intake than tidal breathing and also allowed for quite extensive postcranial skeletal pneumaticity.>>4471287>>4471291>Most pet birds now are much smaller than the average Jurassic bird probably was, meaning much faster respiration and thus perhaps higher sensitivity to toxins in the air.Well yeah we're also not too sure about how close Jurassic avialans were to modern birds, anatomically. They still carried loads of morphological traits that were present in small maniraptoran dinosaurs. Archaeopteryx probably wasn't a very good flyer and probably didn't have as efficient a pulmonary sac system as modern birds, but still had a pneumatised skeleton with air sacs, perhaps evolved by ornithidires or saurischians, and still had the unidirectional breathing that seems to extend all the way back down the archosaur tree. I imagine no Jurassic avialan would have had quite as efficient a metabolism as modern birds, either.
>>4471291>there's also the question of climate and metabolism, since the planet was much warmer then it's possible that metabolism was slower without the extreme needs for active endothermy that modern birds have.That's a good point as well, modern birds, like mammals, have adapted to a Cenozoic world that was both richer in O2/less composed of toxic compounds, and progressively cooler, meaning their efficient breathing apparatus could afford to have a thinner blood-gas barrier, and their metabolism needed to be all the more effective. They are also most likely much more excellent flyers than in the Jurassic or Cretaceous. I feel like the air sac system of true avians is probably an even greater improvement to that which was present in other saurischians, and it has only been improved upon with time, alongside their other morphological specialisations for high-activity, flying lifestyles.So like, to be painfully linear about it, my version of it would go:(perhaps some kind of ancestral unidirectional diapsid breathing??) --> more efficient unidirectional archosaur breathing, as seen in crocodilians --> pulmonary sacs and PSP, as theorised in saurischians and pterosaurs, perhaps ancestral to ornithodira, but probably not and probably just a pterosaur-saurischian convergent homoplasy --> advanced pulmonary sac breathing and PSP as seen in avians, while other saurischians maintain a less derived version, and ornithischians evolve their weird 'pelvic bellows'There would also be a process of changes in metabolism. All of these would be unidirectional breathing, though>these however are unanswerable questions, just as we don't actually know what the lungs of Jurassic birds were like.On god i just want a time machine and a scalpel
>>4471716>>4471302>Basically problems like how the bones supported their weight, or how their hearts pumped blood to great heights, or how they mated, are unanswered questions in paleontology, and perhaps more what OP was asking about.Yeah, I guess my main point about the postcranial skeletal pneumaticity in sauropods is part of an explanation for how they kept their massive bodies up, by comparing it to what we know about living archosaurs and what scientists have theorised about extinct ones. The point is that archosaur anatomy, especially when it comes to respiration, is very VERY different from mammalian anatomy and respiration, so what we know there doesn't directly help us in explaining dinosaur size. Other things, like what we know about biomechanics from mammals, are more useful, of course. There are also other ecological factors across the Mesozoic to do with climate stability and overall greenhouse effect that might mean mesothermic archosaurs did a lot better than they would in the Cenozoic, which has been getting gradually colder for 30 Ma. The stuff about sauropod musculoskeletal anatomy and bone anatomy is still a mystery under investigation, as are other aspects of their biology and ethology. However, I feel like understanding the fundamental unique nature of archosaur ventilation and general anatomy is a good starting point for the how of how sauropods got so large. Just a starting point, however.
>>4471710>https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8260226/The pelvic bellows are supposed to be analogous in musculature and function to the hepatic pistons of crocodiles, btw, but truly unique to ornithischians.>In archosaurian ventilation models, the involvement of the pelvis is ubiquitous, ranging from pelvic rocking in birds (Baumel et al., 1990), to the hepatic piston in crocodilians (Farmer and Carrier, 2000), to the prepubis of pterosaurs (Claessens et al., 2009). Anterior bony projections of the pubic region are key components of these models, including the mobile pubis of crocodilians, and the prepubis and puboiliac complex in pterosaurs. Carrier and Farmer, 2000 highlighted the APP as the integral locus for interpreting ornithischian lung ventilation, focusing their hypothesis on the major genasaurian clades Neoceratopsia, Ornithopoda, and Stegosauria. Macaluso and Tschopp, 2018 hypothesized that pubic retroversion in dinosaurs is linked to the evolution of an innovative ventilatory mechanism, arguing that the plesiomorphic cuirassal breathing proposed by Carrier and Farmer, 2000 constrains the pubis into the propubic condition, and that evolution of mesopubic and opisthopubic conditions indicates a relaxing of those constraints as a new mechanism evolves.So the ornithischian hips and lack of gastralia served a function, I guess
>>4471707>>4471710>>4471712>>4471714>>4471716>>4471719>>4471728I should've been more clear in what I mean by "avian type lungs." We're inferring the existence of non-septate unidirectional lungs based on the apparent presence of air sacs. So while we may not be able to tell when the unidirectional lung evolved in crocs, or if it existed in ornithischians, we can tell in saurischians and pterosaurs based on skeletal pneumaticity. So year, unidirectional lungs can clearly exist without air sacs, and very likely are basal in archosaurs. But the avian system with air sacs is hit and miss. Some have it, some don't.regarding the blood-gas barrier, your idea works but I'd wonder why they evolved a highly efficient method of breathing only to make it less efficient by blocking some gas exchange. But perhaps a less permeable barrier existed over a much larger area, as there's no particular reason the air sacs couldn't have contained parabronchi and some workers have suggested that they did. Birds would've lost most of this pulmonary tissue (but not all of it) as oxygen conditions improved. This is speculation, but it would seem to make sense.
>>4471719Another unsolved problem afaik is the tidal volume and dead air problem in the neck. If sauropods were both inhaling and exhaling through the trachea then their lungs would have to fill pretty much the entire body cavity just to move dead air out of the neck with each breath. Clearly some of this air was being exhaled via the air sacs rather than the trachea proper, but the volume of the air sacs as indicated by the pneumatic pleurocoels of the cervical series isn't apparently large enough for effective air exchange at the neck. Basically with a neck that long, they'd seem to wind up breathing the same air over and over again as the volume required to clear used air out of the neck is enormous. Or they were clearing spent air, but at the expense of some huge fraction of each inhalation and exhalation wasted on simply moving used air out instead of getting fresh air in.
>>4466838It's ok, brah. They all walked off the edge of the world like 900 years ago. It's cool. God bless.
>>4470529>there is an eclipse >get eaten by hideous demon
