Why Were All Theropods Bipedal?
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- เผยแพร่เมื่อ 17 ม.ค. 2024
- We always love interesting questions and one that my eye caught out was why out of every single carnivorous dinosaur! Why were they only bipedal? None walked on four legs full time. Let's
If you enjoyed then I'd appreciate if you like and subscribed!
I do not own any of the footage and images utilized, they belong to their respected sources
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Lucas Attwell
Sources
What is the earliest known dinosaur?
www.amnh.org/explore/videos/d...
Where did dinosaurs come from? www.nhm.ac.uk/discover/where-....
Persons, W. S., & Currie, P. J. (2017). The functional origin of dinosaur bipedalism: Cumulative evidence from bipedally inclined reptiles and disinclined mammals. Journal of theoretical biology, 420, 1-7. doi.org/10.1016/j.jtbi.2017.0...
RUIZ, J., TORICES, A., SERRANO, H., & LÓPEZ, V. (2011). The hand structure of Carnotaurus sastrei (Theropoda, Abelisauridae): implications for hand diversity and evolution in abelisaurids Palaeontology DOI: 10.1111/j.1475-4983.2011.01091.x
Reolid, M., Cardenal, F.J. & Reolid, J. Digital 3D models of theropods for approaching body-mass distribution and volume. J Iber Geol 47, 599-624 (2021). doi.org/10.1007/s41513-021-00...
Jones, T., Farlow, J., Ruben, J. et al. Cursoriality in bipedal archosaurs. Nature 406, 716-718 (2000). doi.org/10.1038/35021041
Navarro-Lorbés, P., Ruiz, J., Díaz-Martínez, I. et al. Fast-running theropods tracks from the Early Cretaceous of La Rioja, Spain. Sci Rep 11, 23095 (2021). doi.org/10.1038/s41598-021-02...
VIRTUAL PALAEONTOLOGY: GAIT RECONSTRUCTION OF EXTINCT VERTEBRATES USING HIGH PERFORMANCE COMPUTING palaeo-electronica.org/2009_3...
#trex #theropod #carnivore #animals #dinosaur #facts #spinosaurus #giganotosaurus #biped
Birds aren't an example of another animal group that is bipedal. They are literally theropod dinosaurs
If you run around saying "ah! Dinosaurs ahh dinosaurs everywhere!" You'll be institutionalized
Birds have gone there own way long enough.
Sure. But then again, by that logic they´re literally fish.
@@Thetarget1 Well, that's true actually haha. Cladistically fish don't exist/are a paraphyletic group. That doesn't mean the paraphyletic grouping isn't useful for us to describe (reptiles are paraphyletic, excluding birds, monkeys are paraphyletic excluding apes) for common names, but evolutionarily, it is more accurate to say birds are reptiles (and theropod dinosaurs), apes are monkeys, all tetrapod descendants are fish. Plus, birds directly inherited their bipedalism from theropods, so I think it's fair to say the distinction isn't necessary (i.e., they are not secondarily bipedal).
@@Thetarget1no it would be like saying we are placental mammals
@@brandonfoley7519 be that as it may they are directly descended from the dinosaurs and as such are the last members of the clade dinosauria you don’t have to like the truth for it to still be true
It's important to note that dinosaur spines didn't flex up and down the way mammal spines do. Mammals use that to increase running speed, but dinos couldn't do that, which put a cap on how fast quadrupedal ones could go.
Never knew that good info
ooooh shit that's actually brilliant. I never thought of that.
An ostrich can move pretty fast
Biomechanics is such an intering field. Thx for info
@@studio1972 Yes, and they are bipeds, not quadrupeds.
Some early crocodilians, rausuchians I believe, had achieved bipedality in the Triassic too, and were mistaken for dinosaurs initially.
I didn't see it mentioned in the video that reptiles have extra muscle attachments between their tails and hindlimbs that mammals don't have. This would seem to be enough to explain why dinosaurs and lizards run on their hind-legs for speed, and mammals gallop on all 4 limbs.
I would be interested in seeing a comparison between the biomechanics of a mammalian gallop and a dinosaur's bipedal run, but I've never seen it. I will make my best guess below:
Argument from modern morphology:
Ostriches are among the fastest animals in the world, so fast that only cheetahs can hunt the adult animal. There were dinosaurs called, "ornithomimids" which had similar body plans. It stands to reason that related animals with similar body plans would have similar speeds, except that the ornithomimids had tails to help them run (remember the muscle attachments). It stands to reason that there were likely dinosaurs who could run faster than an ostrich, which could mean that they were the fastest terrestrial animals of all time.
From physics: In the gallop, the entire length of the body can contribute to the stride, whereas in the run, only the length of the leg contributes to the stride. I think this has benefits and draw-backs. I think for animals of the same weight, a galloping animal ought to be faster than a running animal, if only because of the length of the stride. A gallop also means, however, that the entire body gyrates, which is inefficient. The gyrating motion, although necessary to get the legs in the right position, does not directly contribute to the forward momentum. This, plus the fact that archosaurs have more efficient lungs, makes me think that dinosaurs were probably more efficient runners.
There is also the fact that the fastest running bird alive today (the ostrich) is larger than the fastest running mammal (the cheetah). Also, dinosaurs on the whole were far larger than mammals. This makes me think that the ideal size for maximum running speed may be larger than the ideal size for maximum galloping speed.
There is also the obvious consideration that a quadrupedal stance is more stable than a bipedal stance.
Taken altogether, I think if mammals and dinosaurs could live together at the same time, competing for speed, fast mammals would typically be smaller than fast dinosaurs, and the mammals would be faster for their size than the dinosaurs would be. The mammals would also be able to turn faster and would be harder to knock over. However, the fast dinosaurs, being larger, MAY be able to run faster than their smaller mammalian counterparts (I'm not sure on this point), and they might have surprising endurance.
I think mammals would not be able to compete with dinosaurs for size, so I think all large mammals which could not climb trees or outrun predatory dinosaurs would go extinct, if they were made to coexist with predatory dinosaurs. Smaller sized mammals which were very quick (like hares, or deer) would be able to survive if they could find food, because the dinosaurs would have a hard time catching them. Small predatory mammals like ferrets would also be able to live, because they can go underground. Cats would also be able to live, because they can climb trees. I think it would be very interesting to see how a leopard would deal with dinosaurs. They could climb the trees to stay out of the way of the large dinosaurs, and come down to hunt the eggs and babies when the adults were absent or preoccupied.
There is a detail missing that may change your perspective slightly. Extant large reptiles (aside from birds) do not run on their hind limbs for speed. I am thinking of animals like Komodo dragons and water monitors and the crocodilians. They sprint on all four legs. This might be especially pertinent in the case of crocodilians being the closest thing to a dinosaur we have outside of the birds. I don’t know if this disproves any of what you wrote and I am sure most of what you wrote is in fact well reasoned but this definitely needs taking account of.
Ha, you've legit undermined this video, I love it, I'll go put 10 minutes into AC6 instead, cheers!
@@JohnAvillaHerpetocultural Modern reptiles' limbs are too short to walk/run bipedally, this is not the case for dinosaurs.
@@DendrocnideMoroides that is incorrect. There are many modern reptiles that run in a bipedal gait. For example; collared lizards, basilisks and several smaller monitors run on two legs. My response was directly addressing an item in the original post.
Yeah, the air sacs and light bones in many of them, added by the muscles in the legs and tail, well... makes quite the well-oiled machine
I'm now starting to watch the video. I was actually thinking about this very topic relatively recently; the dinos were around for some astounding 150+ MIL years and none of their carnivorous lineages apparently evolved to be quadrupedal? I've found it quite strange.
because being bipedal is the way to go, look at humans, even though they can wield weapons so could theropods, the only thing that puts as apart is intelligence.
They very well could have and we havent found them yet
I am almost completely sure spinosaurus was not a biped. Taking its limb to torso ratio and head morphology into account I think we are looking at a mostly aquatic quadruped. Why else have the eyes on top? Why else have a jaw adapted to fish? It now appears that it also had a laterally compressed tail like a crocodile. To me it looks like everything points to a very crocodilian like lifestyle for this animal. It should also be noted that bipedalism isn’t really associated with carnivores outside of archosauria. All extant lepidosaurs are quadrupedal or have reduced or nonexistent limbs. Every carnivore in mammalia is a quadruped. Hominids and the still mostly quadrupedal apes are omnivores. All of the amphibians are quadrupeds. I’m not understanding where the idea that bipedalism is the best for carnivores comes from.
@@TyrannusX we are omnivores
Because there were already land crocodilomorphs that take that spot.
Well Triceratops is hypothesized to be more like a pig, being mostly herbivorous but wouldn’t mind feeding on smaller prey or scavenging on carcasses. I think if we ever do find a four legged carnivorous dinosaur, I think it would be an early ceratopsian
All herbivores will opportunistically eat some animal material. Just like carnivores will eat plants sometimes, animals will get the nutrients they needs when they can
Yeah but there's degrees to that@@CAMSLAYER13
This is a very overdone paleoart trend. Isotope studies have found ceratopsians to be fairly typical of those of herbivores. Yes herbivores can and will occasionally eat meat, but that does not mean that it was a staple part of their diet, nor does it mean that they will eat meat even if it is on the table. Herbivores eating meat is a very rare event and there’s no evidence to suggest that ceratopsians were any different. Consistently consuming meat is very bad for herbivores and it’s not like there weren’t plenty of carnivores and omnivores already present.
Omnivores aren’t gonna count for this.
I think animals that specialize in feeding on one or the other of plants or animals ... tend not to be absolute carnivores or herbivores; whatever is digestible is food. Ceratopsians might not really seek out animal eggs, mollusks, and arthropods/bugs but if they happen to be mixed in with the usual plant life it may well benefit the animal nutritionally. Likewise, modern members of Carnivora, including bears, cats, & dogs, might have leaves and berries that contribute meaningfully to their nutrition (though in some cases providing almost no value in terms of calories)
I wouldn't be surprised if a quadrupedal carnivorous dinosaur is discovered in the future. That said, it wouldn't be from the Theropod group of dinos. My understanding is theropod wrists weren't configured in a way to bare weight.
It would honestly be very surprising. If they’ve spent 250 million years on this planet (birds are dinosaurs) and none of them even show facultative quadrupedal locomotion, let alone adaptations for being an obligate quadruped, it would be very unusual for us to not find a trace of them if it was possible.
@@firytwig Not sure what would be gained from becoming four legged as a predatory dinosaur.
@@firytwigBecause two legs is was the way to go, its just better for overall terrestrial locomotion and what helped even more is the fact that theropods had special muscle connections near their hips and tails that made them even more suited for pidedalism
@twinturboray I mentioned that because I stated that dinosaurs lasted 250 million years. If you forget that birds are dinosaurs that sounds a little strange since you would think that they all died out 66 ma. I was simply mentioning that throughout their entire time on this planet zero of their carnivores were at least even facultative quadrupeds.
Also I understand the main comment but even then none of the sauropods or ornithischians show any adaptation for even omnivory. We do have carnivorous and omnivorous sauropodomorphs but those are exclusively bipedal animals.
There's that idea of ceratopsian being omnivorous...
"Why are all theropods bipedal?"
Because they're birds, nuff said
Theropods aren't Birds, rather Birds evolved from the Theropods. And that doesn't really answer the question of why they are all bipedal either.
@@allosaurus_fragilisbirds are theropods.
@@Tyrannosaurus_rex. yes, thats what I was implying
@@allosaurus_fragilisan allosaurus would injure its arms if it tried to run quadrupedal. The only dinosaur I see being quadrupedal is Spinosaurus, maybe? (Probaly not, but it wouldn’t be impossible)
@@DinoFan1993 bro what are you on about
Running on two legs is more efficient and having arms free to grasp at things was a beneficial trait for theropods. In the case of the big guys, the head became the main killing tool & the arms reduced to allow them to maintain a bipedal stance, so clearly there was some serious evolutionary pressure to RETAIN it, rather than move away from it.
I would add that the tail also helps with balance , quadrupeds are more stable yes , but the long tails gave therapods enough balance so that quadruped motion isn't that neccesary . Humans are kind of unstable since we are taller than we are wide or long , but therapods are longer than they are wide or tall , that alone makes their bipedal locomotion way more stable than us
@@ulforcemegamon3094 humans are also quite stable when we need to be since we use our arms for balance, which can make us generally as wide as we are tall when needed.
It is a very interesting topic, since looking at the dinosaur fossil record, herbivores exist quadrupeds and bipeds or both, unlike carnivores, where there are only bipeds.
Glad you find it interesting!
Ancestors of all dinosaurs were bipedal, sauropods and larger ornithischians returned to quadropedal.
4:07 Funnily enough Fasolasuchus, a quadropedal crocodile relative, did reach sizes close to Tyrannosaurus, being around 8-10 metres in length depending on the estimate. They also coexisted with early large sauropod relatives, which might have served as a food source (that's just a hunch btw).
Dinosaurs had generally hollow bones and air sacks like birds (which are of course dinosaurs of that very same branch) and that means they weighted less for the same volume and strength, so they probably did not need quadrupedalism as much as "we" (mammals) do.
So glad you touched on the point about Triassic theropods. A very interesting book I listened to was "The Ape That Understood The Universe". There's a part where it talks about survival of the fittest and how it's not just about who's the biggest and baddest. The biggest piece is about how certain traits are selected for during mating. I would argue that a big reason theropods were bipedal is because that was one of the traits selected for during the Triassic, because theropods that were bipedal got results. Excellent topic sir.
The idea theropods took over in the Triassic due to being bipedal that theropods had to wait until the Jurassic to dominate and that it was the pseudosuchians that dominated the Triassic.
Cos all of them realized the importance of Leg Day.
Most important day
I have been asking this very question for years now in every paleo channel I know of without any answer. Now I finally see it addressed from the one channel I had not been aware of... Well, subscribed for sure.
I think it's because they began as bipedal due to having a comon ancestor with, you know, other bird-type animals. They were bipedal by default. So instead of evolving into quadrupedalism, they instead went the route of being better at bipedalism, which im pretty sure is evolutionarily easier to do
Same, I agree with this.
They're giant birds
They gained so much weight because their food chain dominance, they lost their wings and grew bigger, in ordwe to survive and feed cells, had to eat more in the land.
It says alot on how big the mouth is ==== sky dinosaurs had smaller mouths
Well, thank you very much for dealing here with such an extremely interesting topic!
Best channel for this kind of stuff!
considering near to every dinosaur of triassic was bipeadal, the real question is why they become quadrapead
Mostly because of size, like in the case of sauropods, or they get heavy armored heads like in ceratopsians.
I read this as “Why Were All Theropods Bipolar?”
Honestly, JP movies always made me think theropods had some serious emotional issues, so it checks out.
Nice video. Some of the things you mentioned are a bit outdated but apart from that your channel seems quite good.
Now that you bring it up I started to visualize a bipedal lion/tiger.
I used to think that most dinosaurs especially the raptors would be factulitve bipeds (think of the indoraptor or a bear.) due to their long arms and stuff. This video really changed my mind.
I believe carnivorous dinosaurs were bipedal because it offered them greater bitting areas & angles of their prey along with the ability to press their weight on top of prey.
Not gonna lie, with the bone density, air sacs that helped with their respiratory system, and the way lizards and the like often have muscles between the legs and tails that are well positioned naturally, well.... it makes for very quick, agile hunters, which definitely would give any prey animal a serious run for its money. (Oh, and life, of course. 😅)
Cracking review! 😎👍
Excellent video!
Bipedalism seems to be just a universally beneficial trait for any sort of terrestrial organism that wants to dominate the eco system to a large degree. Especially so for carnivores that tend to be smarter. Not all the time like when you had herbivorous placerias running most of the Triassic at a time and sauropods but as described. Efficiency of movement seems to correlate very strongly with bipedal organisms with carnivorous/predatory traits.
I think modern mammals are kind of the exception to the rule in terms of a long term perspective of time spent on earth successful as four legged like carnivorans and big cats. Which was ended when humans completely changed the game again.
Only Walking on two legs
You’re ignoring that many (though not all, see Postosuchus) if the predatory pseudosuchians that dominated the Late Triassic, the erythrosuchids that dominated the Early Triassic, and the various dominant synapsid carnivore lineages of the Permian were all quadrupeds and managed to be successful and dominant.
It’s really the theropods and the bipedal Triassic pseudosuchians that are outliers in being bipedal dominant carnivores. (And us humans, but we did it through technology).
@@bkjeong4302 how long did the pseudosuchians exist comparatively speaking in the Triassic. As I said they’re exceptions. Mostly in the Triassic tbh as like I said lystrosaurus and placerias were everywhere at one point being herbivorous but the time frame scale is what I’m looking at to make the judgement
@@justjoshua5759
The pseudosuchians dominated until the End-Triassic Mass Extinction.
@@justjoshua5759well, you can pretty much the entire permian being dominated by quadrapedal animals as well. It’s not that one is better than the other, honestly a lot more evolution is down to luck than we realize. Birds with teeth were by far more common than birds without teeth, yet after the extinction none of the toothed birds survived. Does that meen teeth are bad? No. Otherwise how else would the toothed birds completely dominate the small flying vertebrate niche for around a hundred million years? The best answer we have is that it was just by chabce that the ones that survived the extinction happened to lack teeth, and didn’t have a reason to re-evolve teeth. In the same vein it was just by chance that some animals that dominated happen to be bipedal/quadrupedal, and many didn’t have any real reason to change, (although some definitely did)
@@firytwig
Correction; the small flying vertebrate niches were actually dominated in large part by pterosaurs (the idea birds outcompeted pterosaurs as small flying animals is false, as the juveniles of large pterosaurs continued to maintain a hold on those niches to the very end)
Which only further shows that there aren’t “superior” or “inferior” clades.
bipedal movement is more efficient than quadrupedal, hexapedal, octopedal and centipedal movement. It allows for for sharper pivotting.
Thanks for doing this video man can you also do what if jp dinosaurs were actual dinosaurs
That was a whole lot of fun!!!!
3:00 the bottom image is so goofy
5:12 Carnotaurus is a very late theropod. I think it's possible that bipedality may have originally evolved for freeing up the front limbs and later theropods stayed bipedal even when they weren't using their front limbs because they didn't need to become quadropedal again.
The niches for potential quadraped Dinos were filled by Crocodilians going all the way back to the Triassic. They simply didn't have the opportunity to do so.
And for the entire Jurassic and Cretaceous periods they still didn’t have time. Got ya
@@ThemagpieBird734 Crocodilians exist to the modern day, there were no niches for quadraped Dinos to develop.
Quadruped predator isn't a niche. Grassland apex predator, forest burrowing insectivore, etc. are niches.
So if it were advantageous for some theropod lineage to transition into quadrupedalism, they could have done it. And looking at spinosaurus, it certainly seems that at least one lineage did start transitioning.
@@The_SOB_II Ah yes, using the exact same bodyplan as another animal in the ecosystem will have exactly the same selection pressures as utilizing a different bodyplan with different characteristics because you inhabit the same area or eat similar things. Niche specialization is almost entirely tied to physiology, that's something I learned in my Zoology undergrad btw, funny how randos in comment sections try to school me on my own field.
@@bustavonnutz I'm sorry about your degree man. Maybe next time
Id argue its simply the best system for their habits, and over time that stability got better, and we see the Apex of what bipedalism could achieve, and still retain excellent mobility and athleticism in the Tyrannosaurs.
Remarkable trait and what's got me into Theropods simce I was a kid.
If you go back in time far enough, many of the dinosaurs we think of as quadrupeds, sauropods, triceratops and stegosaurs, have hind limbs much longer than their forelimbs, giving us the clues that their ancestors were bipedal, and that they re evolved a quadrupedal stance in order to accommodate a much enlarged digestive system necessary for eating large masses of plant matter.
I thought about this. But maybe because they did not have to evolve quadrepedal motion. Like, we don't ask why cats do not move bipedally.
I think this is exactly the reason. Walking on two legs worked for them, so there was no reason to change. Cats walk on four legs cause their ancestors did, and they have no reason to change it when it works fine.
@@seanmckelvey6618Indeed.
It really makes loons and hesperornithids anomalies in this group as they can't walk bipedally, MAYBE stand for breif periods of time. So they just drag themselves on the ground. Then considering the body proportions, Spino isn't too far off. Water really pushes for weird adaptations I guess.
Thank you.
nice video
My theory is because theyre bipedal they're able to be taller than their herbivore prey. If they were quadrepedal theyd have more mass and in turn need more food which simply isn't beneficial. Carnivores that hunt prey larger than themselves would have a disadvantage if they were also quadrepedal and therefore less tall or simply need too much food to survive and would be beaten by competition.
"Able to be taller than their herbivore prey..."
Sauropods: Are we joke to you?
@@ExtremeMadnessXthey had it good tho, its like getting into the real estate market in like 1989 and years later your sitting on a fortune, that's how the sauropods had it
Dr.James Napoli covered that on if I remember correctly the Therizinosaurus? episode of the Skeleton Crew.
It's a interesting topic of conversation
Frankly when I saw the fictional Indoraptor it always intrigued me. The possibility of a quadrupedal Maniraptorian always seemed plausible. Due to the fact animals of that size could theoretically have a reasonable niche concerning this matter. Akin to large cats or bears.
The reson why there are no quadrupdel is because there where already quadrupdel cardiphores the seudosuchans.
I've always wondered why all carnivorous dinosaurs were bipedal but herbivores could walk on 2 legs OR 4.
Xuanhanosaurus had powerful forelimbs, over 65 cm long; this, along with the retention of the fourth metacarpal in the hand, led Dong to suggest that Xuanhanosaurus might have walked on all four legs. If so, it would be the only known four-legged meat-eater among dinosaurs.
Cursorality holds less support after what Holtz Jr. and others did. If _Carnotaurus_ had a build for speed yet lacked pivotal momentum whilst the T.rex could barely clock up to 30mph to catch up with its prey, what importance does speed serve predators by the end of Cretaceous? Clearly, the herbivores, e.g. Hadrosaurs, could run twice as fast--determining if transitioning from a quadruple posture to bipedal is left debatable.
Aren't you a guy who suggested that sauropods were cause of extinction of dinosaurs?
@@ExtremeMadnessX Seems you've misunderstood. Suggesting that a Sauropod's size in proportion to their dietary consumption were one of the factors responsible for global temperatures to fluctuate, does not imply they were a direct cause in the extinction of their clade completely. However, if people want to start the rumor mill with slander, I can attest the proof from the sources papers/articles I've read.
@@TheMightyN That more imply that sauropods were actually incredibly important for ecosystems if their sheer existence was one of the main causes of relatively stable and warm global climate during the Mesozoic.
I just found a quadrupedal carnivore who primarily ate Brachiosaurus, gonna name him the Snackosaurus Crunch.
The ability to stand erect, allows an animal to scan more terrain looking for prey. The most prolific current meat eater is man, we stand erect.
One additional advantage to being a bipedal carnivore is the ability to alter height and profile at will.
To search, a T-Rex or Allosaur can sit up and 'meercat' its local environment and search for smaller prey hiding in the long grass or brush.
Once such prey is detected the hunter can either run fast (a clear advantage for bipeds) or lower its profile down like some breeds of dogs, wolves or cats and go into ambush mode - i.e. let the unsuspecting prey come to them.
Thus bipedalism gives the carnivores two hunting strategies. A quadruped such as ankylosaur or triceratops cannot do this. Its range of view is limited to the height of the long grass, brush and trees.
One advantage for ADULT long-necked quadrupeds, such as diplodocus or brachiosaur, is that their long neck also confers a good 'look down' position but they do have to live long enough to achieve that height. As youngsters they will be as vulnerable as any other quadruped.
I think that, if carnivorous theropods began reverting back to a quadrupedal stance, they would’ve come into direct competition with crocodilians (which had already carved out that niche).
A popular theory about the reason Abelisaurids' arms were too small to get a grip (Not HLM reference) of their prey is because maybe Abelisaurids might have had colored arms to impress the opposite gender. Also, Abelisaurids' arms were possibly easy to move around, like maybe Carnotaurus made a cute dance with their arms?
That concept is so popular it was shown in all yesterdays. Twice!
@@DreadEnder and Prehistoric Planet though it was only shown in PP because of All Yesterdays
@@theotheseaeagle not necessarily the only reason but prehistoric planet was basically the documentary version of all yesterdays.
😆😆😆
why no mention of silesaurs when considering early dinosaur / dinosauromorph locomotion? there’s also a lot to be said about differences in skeletal structure which should definitely be part of this conversation.
IIRC, a lot of dinosaurs went bipedal, and some of their descendants went quadrapedal again.
Another interesting thing about theropod bipedalism is that theropods and early sauropodamorphs were the only 1 tonne+ animals in history to walk on two legs all the time. Meanwhile ornithiscian dinosaurs went from bipedalism to quadrupedalism as they got larger. I am wondering if the pneumatic bones of theropods and sauropodamorphs allowed them to get large while being bipedal.
Reptiles can't gallop (probably because of gastralia). Mammal spines are more flexible in a vertical axis like a spring while reptiles go side to side. Galloping is a game changer allowing all 4 feet off the ground at once and jumping over obstacles without breaking step.
Crocodiles can gallop.
Kind of a silly question. Based on my limited reading, Theropods are a class of dinosaur characterized by haveingthree toed feet and claws. They are a subclass of suarischian dinosaurs so classified because of their pelvic and hip structure. Theropods are bipedal because if they weren't, they wouldn't be a Theropod!
I personally think theropods ended up bipedally, because their ancestors relied on muscles at the base of their tail (connected to their hind legs) to propel themselves forward.
Because of this, ancestral (quadrupedal) archosaurs had relatively large and heavy tails (compared to mammals and permian stem-mammals) which kept their center of mass towards the back and caused some lines to favor bipedalism.
Perhaps if they didn't rely on tail muscles for propulsion they would've evolved further into quadrupedalism, like mammals.
As for theropod's massive sizes, it might also be related to their stance compared to that of modern carnivores, but that's just my personal belief.
I think there's a soft limit on how large a quadrupedal predator can get and it's around the size of a large tiger, which runs differently when compared to something like a rhino or buffalo.
Any quadrupedal predators larger than a tiger are either omnivores (bears) or special cases (polar bears are hypercarnivores, but hunt marine mammals in a way vastly different from how cats and dogs hunt their prey)
Even in terms of Prehistoric creatures, quadrupedal carnivores larger than tigers are either omnivorous (Andrewsarchus) or only large in popular media (gorgonopsids). The only exceptions I've encountered so far are Sarkastodon (800 kg and only known from a skull) and Megistotherium (a 500 kg Hyaenodont).
As for herbivorous dinosaurs I've also noticed how they were either bipedal (ornithopods, pachycephalosaurs) or had some solid way to defend themselves (horns in ceratopsians, tails in thyreophorans, massive size in sauropods), which for me indicated that bipedal dinosaurs were simply faster than quadrupedal dinosaurs.
Although the defenses of small saurupods are still a mystery to me.
TLDR: Honestly it just feels good to come up with an idea about dinosaurs and then watch a TH-cam video a few months later that practically confirms it.
I wonder if it also has to do with reptile vertebrae moving side to side while mammalian vertebrae moves up and down.
Oh, you should make a video about "Why all mammals are warm blooded"
kindof weird to think that two legged running is faster with how many animals outpace us easily
especially considering how heavy large dinos would have been, giving a great advantage in spreading out the weight during a sprint
also wonder how that changed hunting behaviors since its a lot harder to sneak up on prey as a bipedal dino then a quadrupedal tiger
would be pretty funny to see one try and sneak forward in a squat
but can also not be an endurance hunter once you get so big
but then their prey was also a lot slower and often spikier, so i guess just going brute force would be enough
different targets different solutions i guess
Now name me a bird that walks on all fours. Coincidence?!
The niches that were available for a large quadrupedal carnivore were already taken by crocodilians like Deinosuchus. All the more reason for therapods to stick to their own niches as bipedal carnivores.
Interesting video. Another mystery is why there weren't marine dinosaurs but only marine reptiles.
Spinosaurs were actually filter feeders.
They also reproduce through binary fission.
The Overseer: "Why were *all theropods bipedal* ? "
The Indoraptor: " *Am I joke to you* ? "
Overseer: "Bruh, I'm *talking about REAL Theropods, not hybrids from JW* . "
Also Indoraptor: "Oh, then..." *has left the chat*
I wonder how much damage some of the bigger ones would cause themselves if they tripped while running
silly hypothetical but it’d be so weird if dinosaurs kept on evolving and just slowly lost their arms over time. i have no idea if that’d happen, but it’s just a thought.
I think all the dinosaurs were bipedal in first place (that's why they spread out), the question is why some of them became four legged, the answer is weight stability!
I always wondered this! Cause all the Herbivore Dinosaurs have these unique builds with all kinds of unique features
And Carnivores were just like “Yo I walk on two legs”- XD
If you want to be technical, the closest to carnivorous four legged dinosaurs are the herbivore. Like with the opposite with the carnivores, will sometimes supplement meat in their diet when they don't get the nutritional value they need.
Second,love The video man
Appreciate it!
Dimetrodon has entered the chat.
Dimetrodon is not a dinosaur, it is actually more closely related to mammals.
That's not a dinosaur.
It's a synapsid
mammals put their entire weight on their front legs, so 4 legs works best. The only soul exception was us, because to transferred things to our back, while our closest relatives like gorillas and chimps rely on their front still.
Dinosaur put that same weight on their back, this allowed them the strength to pull up their front and in doing so allowed for the front then to become more versatile for other things and improved reach and flexibility.
If a creature evolves the ability to put weight onto its back legs, it gains huge advantages no matter what. It might slow it down, but, it improves things in other areas. Least thats what I've read.
Simply put the physiological and ecological changes that quadrepedal movement required are enormous and by themselves don't offer any advantages to diapsid predator. Hence why it would be always selected against.
They're using this video to teach real students in High School about Theropods
Bipedalism is more favorable in carnivorous dinosaurs for a number of reasons not described in the video. One, they have better vertical pouncing and are better at concentration force onto prey than quadrapeds. Bipedals are better at long distance pursuit of prey while quadrapeds are better at either short distance sprint as described in modern predators. In modern herbivores and predators, time is of the essence; the longer a chase lasts, the less likely a successful kill is going to be made. The opposite is true in the dinosaur world. Quadrapeds had to sustain their body weight and avoid predators which consumed a massive amount of energy. Bipedal predators did not need to outrun their prey; they just needed to wait long enough for their prey to run out of energy. The prey item that carnivorous dinos did have to be quick about killing would have been stegosaurus that had wandered too far from the pack. Being able to pounce and knock over an unaware stegosaurus would lead to an easy kill. Either that, or being able to outmaneuver a charging stegosaurus would also pose advantantagous. Terror birds could swing their head in the direction they want to go to swiftly change directions, and the same could be said about bipedal carnivorous dinosaurs.
Let's all remember that birds are theropod dinos, and there are no quadruped birds, not even among the land ones. Terror birds were carnivorous and dominant in south America for dozens of millions of years.
I did the illustration that you used in the thumbnail, credit me in the description of the video
Also wonder why there aren’t a lot of bipedal carnivores (not including birds or us) assuming it’s because 4 legs are faster than 2
I want to know how such large animals could get up off the ground without forelimbs. Even a chicken uses its wing to get up after laying down.
It's only a matter of time before carnivorous dinosaur remains are discovered next to a 95million year old bicycle. Just saying.
I always though they traded arm weight for head weight.
So they couldn't gorge themselves on sauropod but there are other ecological niches even back then like wide ranging herbivores
The walk on two legs cause they wanna hug you 🥰
I mean. if you're talking about... a full ecosystem. pterosaurs were quadrapedal. and crocadilamorphs existed already. Yes dinosaurs were the major predators, like mammals are today. but i would argue the numbers split was fairly similar to a reverse of modern day. there were a LOT of pterosaur species. in a WIDE variety of sizes. in some environments they rivaled the apex theropods during the late cretaceous. saying "why are all theropods bipedal" is like saying "why do all mammals have fur" that's simply a key trait of that evolutionary family
I believe in modern day humans are the only bipedal exclusive mammalian predators. so mammals have the same situation in reverse going on. and lets be real. humans are Really Weird compared to other mammals and even other apes. we're the outlier here
The argument that theropods would 'lose agility and speed' if they evolved into quadrupeds is not supported. In the modern world, quadruped maximum speeds are much higher than the fastest bipeds. And cheetahs seem pretty darn agile to me.
I think my bipedal is the template of hunters for the animal kingdom
Lots of things skipped over in the story, ..the way nervous systems are arranged for different aspects of predator-prey attack and defence when competing for resources. Have to start somewhere somehow.
Small arms are for navigating their immediate environment
Yes
Theropods were bipedal so they could strut like badasses.
Do a collaboration video with TheDinoFax
Dat bird body plan
I'm guessing that most of the quadrupedal apex predators in the Mesozoic were suchians.
the argument made for "agility and speed" on 2 legs makes 0 sense. A quadruped animal can move better with better distributed weight, and we can see that clearly in today's animals.
Now sure our largest animals are all slow, but thats because they are herbivores who dont need to run or move that much. Doesnt mean a 4 legged predator is unviable.
I think it was a mater of coincidence, the first dinossaurs had selective pressure as small animals and therefore as they climbed up the food chain they just kept the trait as it wasn't a real problem.
Large creatures on every other faction were all quadrupeds.
edit* just saw a rly clever comment below. Apparently dinossaur spines weren't flexible like mammal's are, so unlike mammals they couldn't use it to provide force when running, which capped their speed when compared to every other faction. Actually brilliant.
Are there or have there been any animals that walk on the front limbs?
I might have seen something in marine bottom dwellers and someone could argue that for the mudskippers. Don't remember on top of my head at 2am now though. Time to sleep.
that’s really interesting. maybe seals, right? their back legs are all flipper.
Birds and humans are bipedal now .
I mean they came up with the name to describe the class of biopedal dinosaurs soooooooo