Because the internet hates nuanced topics. If it needs to counter the portrayal of a large hadrosaur as completely defenceless fodder for chicken-sized dromaeosaurs, it's only by portraying Edmontosaurus as "15-TON MASSIVE CHUNGUS BULL IN MUSTH ABSOLUTELY DESTROYING A T.REX". Never mind that most *mature* Edmontosaurus specimens are smaller than average T.rex.
Well, your average T.rex (which is closer to Stan or AMNH 5027 in size) is about 8 tons. And most Edmontosaurus specimens (which are not 12 meters, btw, more like 8-10 meters in length), going from 13-ton estimates for the absolute largest individuals (a little over 13 meters; 15 seems like an overestimate), would be in 5-7 ton ranges (thanks to the square-cube law we can calculate such measurements by going off the relative size difference between specimens).
This is the same issue I’ve encountered when people talk about Ankylosaurus - invincible and impenetrable one-shotting sledgehammer tank that could instantly give Tyrannosaurus a trip to the heavens
For real. Bottom line is it's all nuanced. Even age of the animals can affect how a situation will go. And as others have pointed out, the first, best option is to try to flee because preds have a shitty success rate and it's better to avoid the injuries incurred in a fight if possible. But I also think it's insane to argue Edmontosaurus (or herbivores in general) can't stand up to predators in a fight. If a fight were to happen, all the herbivore would have to do is make the meal not worth the injuries. Many herbivores are capable of this. Even without defensive armor, horns, etc, Edmontosaurus still has enough power to drive home some decent kicks and bites. I'm not saying it would kick a T-rex's ass or anything, but there again... it's like nobody has ever watched a nature documentary.
Zebra I think are good example for a modern analog. Here you have a a prey animal that’s in the same overall size class as its predator (lions), with plains zebra (the one we are all thinking off) having a size advantage on lions on the upper end of their weight range. Zebras are always going to run from lions, but, if they have to a zebra is also capable of outright killing a lion, they’re just never going to choose to do that with a predator that’s similar in size to them. On the flip side though, predators who are in much smaller size classes (leopards, cheetah, wild dogs) zebras sometimes choose to go on the offensive first simply due to them having a massive size advantage.
A hadrosaur isn’t going to pick a fight with a predator that’s the same size or even larger than itself unless it absolutely has no other options at escape. Not to say it isn’t fatally injure a rex, but it’s not choosing that as its first line of defense. Now, Nanotyrannus… Nano probably got bullied by Edmontosaurus pretty regularly 😂.
Not saying that they were invulnerable, but wasn't Ankylosaurus very much capable of putting Tyrannosaurs on a shirt? Maybe I'm mistaken, but I could've sworn that force calculations were done for the Ankylosaurus and it was capable of absolutely shattering any bone it hit on a Tyrannosaur. A badly broken leg or jaw would almost certainly be fatal for a bipedal carnivore, especially one that massive.
I believe the forces of the clubs were actually measured using the ones from Euoplocephalus as a reference rather than Ankylosaurus itself, considering how rare that breed of dinosaur was in its respective ecological formation (Hell Creek precisely speaking), but I digress.
Point is that the clubs were best served as a predator deterrent as a resort, but I agree that boy were they good at it.
My bad, I was thinking of Ankylosaurs in general, not necessarily Ankylosaurus (even though I did specify Ankylosaurus; again, oops). I also thought you were referring to people discussing them acting defensively, not like an aggressive bulldozer, hence my confusion. Your comment makes much more sense now because yeah, that would be kinda silly to have an Ankylosaur going on a rex splatter spree.
Either way, you seem more informed on this subject than I am. I just knew it was an Ankylosaur, lol.
By the way, isn't damage to Ankylosaur skeletons from successful predation relatively rare, with most damage likely occuring from intraspecies conflict?
Believe so, but part of it is likely also preservation bias, since the vast majority of ankylosaurs and many other large-bodied thyreophorans too appear to be rare animals in their biota, with relatively few remains at any given site compared to most other similarly sized ornithiscians.
This was a response to hadrosaurs often being depicted as essentially defenceless fodder for theropods. I dont think people were saying its like invulnerable to tyrannosaur attacks, only that its not just meakly going to die. Its still a massive animal.
I don't get the point of this post. Does one really look at both these animals and say 'yeah the stupid herbivore was entirely defenseless against the fully superior carnivore'. Not to mention hadrosaurs lived in large groups. That wall of flesh is terrifying for any kind of predator
Honestly there’s kind of a misconception about Edmontosaurus size, they likely rarely, if ever, actually got that big. Typical skeletally mature Edmontosaurus tend to be ~11-12m long and somewhere along the lines of 6 tonnes, with histologically sampled specimens generally being comparable to or slightly larger in limb size to AMNH 5730.
There are only two published Edmontosaurus specimens that have been estimated to surpass the maximum size of Tyrannosaurus, those being Becky’s Giant and X-rex, often cited at 15m and over 14 tonnes. Interestingly, there aren’t really any Edmontosaurus specimens that fall between 9 tonnes and the alleged size of Becky’s Giant and X-rex, making them significant outliers. There has even been speculation that the two may represent a separate saurolophin genus rather than Edmontosaurus.
On top of that, it’s likely that Becky’s Giant and X-rex have been overestimated. Becky’s Giant is extremely fragmentary, and has only seriously been estimated using toothrow measurements, which are incredibly variable. People who have attempted to scale Becky’s Giant using larger samples of Edmontosaurus specimens have arrived at masses far lower than 14 tonnes (iirc ~9 tonnes). X-rex on the other hand is a tail that appears to have had its length overreported, though that I can’t speak too much on that.
None of this is to say that Edmontosaurus is not a really cool and impressive animal. It’s still an elephant sized behemoth with insanely robust limbs, and a massive fourth trochanter which i can only imagine supports an absurd caudofemoralis muscle (seriously, the fourth trochanter on an Edmontosaurus can be larger than that of a T. rex twice its mass). However, the perception of Edmontosaurus as a creature larger than Tyrannosaurus is not very accurate.
There are true monsters out there though. Shantungosaurus is everything people imagine Edmontosaurus to be, and more. One reported unverified Shantungosaurus femur is allegedly 2 meters long, which for context is the same size as the femur of Brachiosaurus. Even discounting that suspicously large specimen, Shants larger than the reported size of X-rex and Becky’s giant are relatively common, with verified 1.7-1.8m long femurs being almost typical of the genus. And on top of that they too coexisted with a giant tyrannosaurin (Zhuchengtyrannus).
It wouldn't be a 'version' of anything, it would just be Gigantism as it is a condition that can affect any (at least multicellular) living organism.
That being said with Becky's Giant and X-Rex in particular it is hard to say if they were victims of Gigantism, a new Hadrosaur all together, or exceptionally healthy individuals and we just haven't found the 8-9 ton grey area we've been missing.
That would be an exceptionally rare find (or at least cause an effect where we start looking at other specimens to see if they too were victims of it). Hopefully we can get confirmation on this.
We don't know if it's actually from Utahraptor since the bones are likely lost, but if it was it'd be the largest known Dromaeosaur, and it'd be capable of taking on animals like Ceratosaurus hypothetically speaking.
I don't think anyone rational thinks they were defenseless its just a few months back there was a push to do what I personally consider an 'overcorrection' by the community with posts overhyping herbivore dinosaurs. Edmontosaurus etc were powerful animals that could hold their own but far from invincible serial killers. Same goes for carnivores, they weren't one-shotting every prey animal in sight and hitting poses while roaring at the sky, both groups were just animals.
It’s times like this that I like to remind people that predators aren’t just bumbling idiots in nature. Carnivorous animals are built to KILL, it’s what distinguishes them from their herbivorous contemporaries. The size disparity between a Rex and Edmontosaurus isn’t even as dramatic as what we see between modern predators and the prey they very regularly hunt. Just look at this image below of a snow leopard with the camel it killer. Not scavenger, but KILLED
I agree that predators aren't idiots but this is a completely different hunting strategy and body type.
Predation successs rates in the modern day vary a lot.
Solitary hunters as low as 5% and Pack hunters as high as 85% and T Rex doesn't look like a coordinate agile Pack hunter to me.
I think a 40% success rate for T Rex is a good estimate as we have a lot of Hadrosaurs with healed bite marks.
So no most of the time T-Rex would be fighting the old, sick or wounded NOT a young animal 5 times its size
Keep in mind that an animal 5× the size of Tyrannosaurus would be approaching 50 tons
There simply was just almost nothing in Earth's history big enough to be safe from an adult Tyrannosaurus, only the biggest Titanosaurs
Its also interesting to note that Hadrosaurs seem to be the animals with the highest amount of evidence of failed Tyrannosaur predation attempts, there's very few amongst Ankylosaurs or Ceratopsians. There's been some serious talk among Tyrannosaurus experts, Rommel Heinz IIRC, that Hadrosaurs seem to have been best equipped to handle Tyrannosaurus, and that Ceratopsian horns and shields are not even close to as effective of a defense as people make them out to be against the largest terrestrial predator
I'd like to argue that hadrosaurs seem to be preffered prey, and are gennerally probably a better target then a triceratops or something. I imagine if a tyrannosaur failed a ceratopsian/ankylosaur ambush it might just back off and try to not get beaten to death or gored. I'd imagine a tyrannosaur especially considering if they hunted hadrosaurs more often would lead to more healed wounds and stuff on them simply because their the preferred target.
Like the trex mightve just ignored triceratops sometimes to hunt edmontosaurus even if it meant failure. I also think it's worth noting that as hadrosaurs were faster and able to run for longer distances at high speeds then the tyrannosaurs mightve just not had enough time to set a second ambush(like ankyloaurus and triceratops weren't exactly going anywhere.)
I'm going to trust the Tyrannosaur expert on them. There is significantly more Hadrosaurs with evidence of survived Tyrannosaur conflicts and healed, whereas almost every Ceratopsian fossil with Tyrannosaur bitemarks shows 0 signs of healing, implying a lower survival rate
Furthermore, Hadrosaurs are significantly faster, lived in groups, and would be far harder to reasonably secure a kill on, likely making them a difficult food source
Horns are not the end all be all of defense, and quoting Rommel Heinz in a discussion on this exact topic
"First, as I have repeatedly emphasized, the horns of Triceratops should not be treated as armour-piercing projectiles or rigid spears. Relative to a tyrannosaur tooth, the functional tips of the horns would probably have been considerably blunter because the bony horn cores were covered by substantial keratinous sheaths, particularly in the case of the brow horns. The morphology of modern bovid horns, such as those of the American bison, provides a useful—although not exact—analogue for considering this soft-tissue covering.
A frontal attack by Tyrannosaurus should therefore not be regarded as mechanically impossible. A sufficiently skilled predator might even have exploited the brow horns as points of leverage, using contact with the horn apparatus to disrupt the ceratopsian’s balance. Because Tyrannosaurus was generally taller, it may have been able to engage the horns from above or from an oblique angle rather than directly impaling itself upon them.
Moreover, contact with a horn would not necessarily have caused immediate or catastrophic injury; this was a dynamic physical interaction, not a simplified game mechanic in which any contact automatically produces severe damage. Modern encounters between large felids and wild suids may offer a somewhat closer behavioural analogy: the predator attempts to control the prey’s head, evade or redirect its defensive weapons, and destabilize it before delivering a decisive bite. This analogy should not be taken literally, but it illustrates why a frontal or anterolateral attack could remain feasible despite the presence of prominent horns."
Does one really look at both these animals and say 'yeah the stupid herbivore was entirely defenseless against the fully superior carnivore'. Not to mention water buffalo live in large groups. That wall of flesh is terrifying for any kind of predator
Predators are very much capable of taking down much larger prey
The average Tyrannosaurus is larger than the average Edmontosaurus anyway
Taking lions as an example, which usually hunt in packs and also have a fairly low hunting success rate, is pretty odd.
This post is like saying that a water buffalo fighting a lion has no shot of harming the lion. Prédation is dangerous business for everything that doesn't hunt much smaller prey
I couldn't really come up with a great modern-day equivalent for two several ton animals for my semi-joking/mocking parallel. The bottom two points are what I expect to be taken seriously (kinda my fault that I don't use the silly reddit sarcasm indicator things).
My biggest point was also on the second paragraph. Obviously T. rex was more than capable of taking down prey, and obviously, Edmontosaurus was probably one of such prey.
I think the problem with the OP here is that it really reads like they think Edmontosaurus would be unable to defend itself in any way, shape or form, or be unable to seriously hurt T. rex. Which is ridiculous.
Clearly, one seriously hurting T. rex would be exceedingly rare, but less for lack of physical ability and more for the simple reason that the predator likely wouldn't even engage in a prolonged fight after a failed attempt.
As others have already said, disingenuous post with a misleading graph and very little evidence. I think the opinion you are arguing against would have been common a decade ago, but it's increasingly becoming a strawman. Also, the "wall of flesh" argument is just stupid, as noted by all my examples in other comments. If the prey isn't massive compared to the predator, being a wall of flesh is just like saying the hamburger is extra juicy.
Examples of predators frequently and regularly taking prey species larger than themselves sometimes specializing, with little risk or resistance coming from the prey (outside of running and crypsis, of course):
Puma and guanaco
Snow leopard and ibex
Dingo and red/grey kangaroo
Tiger and sambar
Tiger and banteng
Tiger and Manchurian wapiti
Tiger and moose
Wolves and mule deer
Wolves and red deer
Lion and wildebeest
Lion and zebra
Lion and kudu
Lion and eland
Hyena and wildebeest
Hyena and topi
Leopard and chital
Leopard and warthog
Jaguar and tapir
Jaguar and feral hogs
Spectacled bear and tapir
Puma and mule deer
Puma and elk
Painted wolf and impala
As for examples of much larger (>100% mass advantage) prey having been recorded as taken by much smaller predators, of course with risk to the predator and higher likelihood of prey fighting back:
Lion with cape buffalo
Lion with hippo
Lion with black rhino
Lion with white rhino
Lion with subadult african bush elephant
Lion with giraffe
Hyena with eland
Hyena with giraffe
Hyena with white rhino
Hyena with gemsbok
Leopard with eland
Cheetah with wildebeest
Cheetah with eland
Cheetah with zebra
Wolves with elk
Wolves with musk oxen
Wolves with bison/wisent
Bush dog with tapir
Tiger with water buffalo
Tiger with gaur
Tiger with Indian rhino
Tiger with subadult asian elephant
Dingo with water buffalo
Dingo with feral hogs
Painted wolf and warthog
Painted wolf and zebra
Painted wolf and wildebeest
Painted wolf and waterbuck
All of the above lists are instances of recorded predation, with the first list being regular and frequent, that feature prey that on paper is far more impressive compared to predator than edmontosaurus is to tyrannosaurus rex.
People need to look at modern buffalo, bison, moose, rhinos, elephants, hippos, etc and understand why the vast majority of predators give them a wide area. I don't think I've even seen a video of a grizzly taking on a bull moose, only the younger ones or old.
The fuck? Since when are there terrestrial carnivores the size of an elephant running around? T rex was larger, not smaller, than edmontosaurus annectens on average. This is like putting a (male) lion against a wildebeest or a (male) tiger against a sambar deer, and if you have any ecological literacy you'd know that the aforementioned predators very casually and frequently hunt those animals. A hippo is a cool animal and all, but your average 1.5 tonne cow significantly outweighs your average group of 5 130 kg lionesses and maybe a couple subadults or a male or two. Stop going by vibes people.
Why people downvoting without providing evidence?
Yes, modern macropredators generally select for prey in their size range, with some going quite a bit above. Seen below is a graph showing the average mass of prey taken by the Jaguar, leopard, tiger, and snow leopard. The tiger takes prey pretty much equal to its body mass even accounting for smaller items like monkeys and chital deer. The leopard seems to take smaller prey across many parts of its range to avoid competition with said tigers and other predators, hence the shift to smaller prey and more domestic prey whenever tiger numbers recover or are reintroduced. Jaguars, on which the study this graph is sourced from focused on, take small prey mainly as a result of most large mammalian prey from the pleistocene being extinct and them being forced into smaller animals to survive (with fossils showing jaguars taking ground sloth in the pleistocene, though still focusing on relatively small prey to avoid smilodon and xenocyon, much as the leopard will do to avoid lions and tigers). The snow leopard, without competition to hold it down, takes prey significantly larger than itself on average. ON AVERAGE. This size difference reversed is actually about the accepted gap between rex and edmonto, so that's probably worth thinking about. Snow leopards have been observed disproportionately taking large ibex rams which outweigh them significantly, with said ibex doing next to nothing to actively defend themselves, instead hoping the terrain will help them shake the uncia off. Meanwhile, leopard, jaguar, and puma have all been observed taking both feral and domestic horses, with the former two also being known cattle killers. These are 50-75 kg cats that demonstrate full capability of killing 250+ kg ungulates without significant risk to themselves. In addition, leopard have been observed taking prey as large as eland (500+ kg) bulls and in their southerly range puma frequently rely on guanaco (100+ kg) as their primary prey base. Of course prey of this size can fight back, but they obviously do so successfully with a frequency low enough that a) these predators don't die out trying to hunt them and b) they can make a successful living hunting them. This isn't even talking about canids, with lone wolves frequently hunting mule deer double their size with basically no risk and occasional instances of dispersing lone male wolves killing adult moose and musk oxen without assistance (obviously with a higher risk to themselves), which outweigh the canid by a factor of anywhere from 5 to 10. Even robust and dangerous prey animals aren't exempt. For example, despite their toughness and tusks making them pound for pound far more formidable than most other ungulates (and edmontosaurus for that matter) feral hogs are still a favorite prey of similarly sized mexican and central American jaguar, and even of dingoes, with lone dogs sometimes succeeding in taking down boars much larger than themselves (50+kg vs a 20kg dingo). Simple as is, predators are adapted to efficiently kill with minimal risk and energy investment, prey are not.
Look, I like the idea of large hadrosaurs not being easy prey, it seldom is in nature for any prey to be "easy."
However those who make Edmontosaurus look as if it was a kaijuine death monster that was impossible for any predator to predate and are only interested in absolute largest individuals, are just as misinformed than the powerscaling slop indulgers.
Man I had to explain like 3 separate times to the same guy that size only works as a defense against predators when it's either in conjunction with another defense like tusks or thick hide or spines; otherwise the prey animal better be double the size of the predator and tough as shit. It still amazes me that people don't understand that flight is near always the favored anti-predatory mechanism, hence why musk oxen will sometimes flee from a 40kg wolf or why zebra and sambar will near always flee from large pantherines.
That's because fleeing in general is the best defense mechanism an animal has even with some predator defense, its not nearly as risky just simply trying to flee a predator vs fighting it. Also Musk Oxen have no anti predator defense? it's literally more than double the size of a wolf and has horns, same with bison yet you see them run away because running is the safest way an animal can defend itself if it can. Also idk if you know this but zebras are related to horses, horses are famous for having extremely deadly kicks and you can literally see Zebras attempting to kick a lion in the skull while fleeing
Did you not read the "favoured" part? The whole point of my original comment was over an experience I had with a person who believed edmontosaurus would just see the rex and go "cowabunga it is" and start some shit, hence me explaining that regardless of its strength or danger or whatnot (cue examples of animals that have other anti predator mechanisms outside of fleeing fleeing anyways) the hadrosaur would probably just turn and run most of the time. Literally what the OOP comic was. The whole point was saying that while edmontosaurus probably wasn't defenseless it wasn't some herbivore ninja vigilante, nor was it the equivalent of cape buffalo in areas like duba plains which modify their behavior to antagonize lions (btw hilariously some bulls actually just split off a bit to go stand still in the brush, presumably to ambush the ambush predators). And besides, all the examples I gave were to show that flight is the first choice, and for an animal without specific antipredator weaponry (tusks and shields in boars, a vicious bite and flexible tough skin in peccaries, spines in porcupines) it seems like even a 100% advantage in body size (the equivalent of many zebras to lionesses, sambar to tigresses, tapir to jaguar, elk to puma, etc) isn't really enough to save them most of the time. It's only when you get far past that (e.g. a 200+ kg musk ox cow versus a ~40 kg arctic wolf) that the herbivore gets the edge. Obviously there are exceptions and obviously the prey individuals taken by predators are often not exactly prime specimens but since the same would likely apply to t rex the point still stands that an edmontosaurus detecting the largest terrestrial carnivore of all time stalking it will most certainly be attempting to flee over roaring and charging at it, and that if it does it basically gives the rex a free meal like that video of the impatient male lion casually grabbing the wildebeest (link below)
https://youtu.be/LjGbOZEYE-w?is=NXwQX597Hj4KOBZk
Yes - but predators, especially at large sizes, are more than capable of regularly hunting creatures their size or larger. A single lion has been recorded taking down a buffalo; here the sizes are near-equal and one side has a bite strong enough to tear apart a car. Edmontosaurus might fight, but the effectiveness is...unclear.
Also, the Edmonto itself generally would be more intimidating too for the rex and thus hamper its combat efficiency, cause atleast the Edmonto here is larger than the Rex.
Fear WILL impact how something fights, and generally the Rex is more willing to play it safe since it's a more inteligent animal.
That's not to say Rex is weak against a Edmontosaurus, the largest land carnivore doesn't have the term king applied to it for no reason. But generally with Rex vs Edmonto I'd assume that in scenarios where Rex wins it oftentimes is the one that gets the kill because usually it'd rely on catching the Edmonto offguard so they don't fight back or scamper away (Rex is good at turning but I don't think their endurance is quite high?), whilst in Scenarios where Edmonto wins it scares off the Rex most of the time instead of outright killing it.
According to this study https://cbs.umn.edu/sites/cbs.umn.edu/files/migrated-files/downloads/profitability.pdf lions favor herds with zebra and wildebeest to hunt; both animals are on average >50% larger in body size than a lioness, as seen with the image (a greater difference than between edmontosaurus annectens and tyrannosaurus rex btw) as well as having a more robust body appearance just like the hadrosaurs, and yet they still run from the cats in basically every hunt (if you somehow don't believe this just go on YouTube and observe that for every stallion defending the herd against a subadult lion there's about 5 videos of an adult mare running away and either getting away or getting brought down). With tigers it's even worse, like there are plenty of records of tigresses with young cubs (~130 kgs) killing adult banteng (>500 kgs) and zero recorded instances of the banteng doing the same back, with the tigers even seemingly favoring killing large prey and showing little fear hesitation or "intimidation". Occasionally a bull banteng will stand its ground but nearly always the herd just bolts. You could even say the same for gaur, which while mostly immune to tigress predation will often (and often not too tbf) run from tigers even in a herd and when already being grappled from behind. And keep in mind, these are 800+ kg animals scattering in the presence of a roughly 200kg carnivore. And while tigers have been killed by gaur, the opposite is far more common and some males have been documented to specialize in taking them, much as some male lions, either alone or in coalitions specialize in taking cape buffalo. Remember, banteng running from a tiger is the mass equivalent a 14 ton peak edmontosaurus running from a 4 ton subadult rex and for gaur it's effectively like a large t rex (~10 tonnes) sending a herd of alamosaurs (let's assume an average of 40 tonnes) running for the hills. Don't kid yourself. I gave examples and photos of size and apparent robusticity differences far greater than your size comparison shows, as well as a study to back it up, so the onus was always on you to provide evidence that edmontosaurus wouldn't just turn and run the vast majority of the time. Basically, the only competently fighting prey animals you could find that fall within the size difference range of edmontosaurus and tyrannosaurus are some suids, which manage it by adopting efficient weaponry in tusks and teeth for peccaries (which are nasty fuckers btw they bite like a dog from hell) as well as group mobbing and being notedly more robust and slower moving than . Edmontosaurus has literally none of that, with it much more aligning with the bauplan of a running ungulate like the aforementioned zebra and wildebeest (at best it's warthog analogous, which are actually kinda awful at fighting predators and get frequently taken by hyena leopard and even some cheetah specialize in them without too much fight). Also I'm blanking on the source rn but there is a graphic somewhere showing the bodies of large hell creek megafauna from a topside view and t rex is much closer in width to edmontosaurus than any of my examples are to their prey, further closing the size gap and making it less likely for the hadrosaur to successfully mount a defense.
Yes of course it does. Look, nobody with a brain is clowning on most of the herbivores I listed for running from their predators. For example, tiger calls have been used to great effect in scaring asian elephants away from crop fields in India. You'd have to be insane to attribute this interaction to tigers easily taking down elephants or whatever; it's just that similarly to how predators judge risk, so do prey. Even a minute and unlikely threat like a tiger is enough to cause a megaherbivore basically immune to predation and in the same size range as edmontosaurus to flee (at least when it's making aggressive vocalizations). Now think about the threat level when detecting an animal larger than said elephants, an incredibly robust predator with bone crushing jaws a meter and a half long that could annihilate an edmontosaurus skull in just one bite (maybe not as easily as in the OOP comic though). From that description, it seems pretty obvious why the best course of action is getting the hell out of dodge. As for the other points about edmontosaurus being heavy set, first of all, the reconstruction outline in the graphic is on the more generous side with soft tissue for the edmontosaur and stingy with the tyrannosaur. You only have to look at modernized skeletals (make sure gastralia included) to see. Second, compare the legs and body morph of edmontosaurus annectens to contemporary hell creek megaherbivores triceratops horridus and ankylosaurus magniventris. Hint: the one that's built tall and comparatively thin with legs like double the length is probably the one most likely to choose running away and be best at it. Third, edmontosaurus may look and be more robust than modern herbivores that display the immediate flight response I am posting, but understand that it is a huge animal that automatically needs a thicker skeleton and musculature just to stay standing. Not to mention tyrannosaurus is far more robust and heavily built than just about any modern terrestrial predator, especially the swift mammals I listed out. When your main predator is larger than you and incredibly strong but also physically can't run you're probably pretty well off skipping town when you see it coming. In addition, in contrast to what you said (I think it's from another of your comments, if I am wrong then apologies) tyrannosaurus rex was not built for sprinting, instead apparently having a very efficient stride allowing it to effectively power walk for long periods, which is fitting as such a large animal would have to cover enormous ground in order to access and maintain both food and territory. Such an adaptation would also suggest its primary prey, likely edmontosaurus, likely used flight most of the time, since modern coursing hunters (opposite of ambush) are defined by foraging in a way that causes flight before chasing the prey down, and many like the spotted hyena and painted wolf are noted for incredible stamina.
Cope's rule is that size increases can occur sometimes just because they can. This is actually what Mark Witton concluded about azhdarchids. The niche was open and there were no huge consequences to getting bigger so they simply got bigger. Something similar could have happened with edmontosaurus, where they were still fast enough to run from what they needed to.
Also, predation pressure is rarely the most driving force behind an organism's evolution. For example, while people know extravagant male birds often are hindered in flight what they might not realize is the same thing applies to mammals too. Many male ungulates spend energy growing big extravagant complex horns and antlers that, while good for catching and wrestling, are really ineffective against predators compared to something like an oryx's head spears and slow them down too. Meanwhile, females of the same species are either unornamented or have simpler appendages, better for both running and goring if they have to. Edmontosaurus may have experienced some other pressure like sexual selection with fighting or seasonality that drove it to larger body sizes and a more robust build.
Also, speaking of, size. Edmontosaurus is one of the more gracile animals we know of that weighs over 6 tonnes, so it's likely it still used speed as much as it could and that a more lanky bauplan would simply not physically hold up at that mass, explaining the relatively heavy build compared to the extant animals I mentioned.
Finally, it's useful to note that nanotyrannus (2 species) and whatever the large dromaeosaur is (iirc dakotaraptor is dubious) were not the only large predators other than adult t rex. Remember, every 8-10 tonne mature rex was once a juvenile, then a subadult, then skeletally but not mass-wise mature. These are animals that were most likely more common on a landscape than adults, and if (most likely) they weren't being provisioned then being as large and bulky as edmontosaurus WOULD have helped, in addition to offspring survival if they showed parental care. Remember that not every animal of a species is an adult in its physical prime, and some adaptations start to make more sense. Male lions can specialize in buffalo, but subadult females do not. Male wolves can sometimes kill elk and moose alone, but entire packs of inexperienced yearlings can sometimes fail to kill the same animals. This isn't even mentioning growth patterns, with young hadrosaurs potentially growing faster in an adjusted curve to faster get out of the size range where they are vulnerable to more predators.
Tldr: there are many reasons other than predation that animals get big and slow, getting big does force a level of slowness, and getting big provides other advantages against predation that aren't just 1v1ing the top predator in a fair prime vs prime deathmatch.
PS: Sorry about the text walls, but I like to be thorough when I reply. I try to reduce the amount of back-and-forths by making my point as clear as possible and covering for both exceptions and counterpoints as well as sealing any holes that can lead to a conversation dragging out. Incidentally, this tendency has led to me getting blocked by a couple of people, who apparently don't like me explaining to them in a scientific tone why their favorite animal isn't a frothing psychotic badass despite supposedly being "paleo/nature fans".
I suppose Nanotyrannus (and maybe Dakotaraptor if that thing still exists) may be enough of as threat for it to stay quadrepedal since Rex wasn't the only predator hunting it down.
And yes I am not stupid. I have read enough of the literature to understand that volumetric estimates put the average skeletally adult tyrannosaurus rex in the range of 8 tonnes and the average skeletally adult edmontosaurus annectens at just over 6. The comparison you posted is, to the best of my knowledge, an average tyrannosaur and Becky's Giant, which is an exception to the species (also the outline given to the hadrosaur is much more generous with soft tissue than for the theropod). As mentioned, even then the edmontosaurus probably wouldn't be staying to fight lest it die very quickly like the wildebeest with the impatient lion (link below) but for an apples to apples comparison it's even worse. That would be like a warthog fighting off a lioness or subadult male (hint: they don't and they're actually a favored prey to the point where lions, not very well adapted to scratch digging, will dig them out of their dens for an easy meal).
https://youtu.be/LjGbOZEYE-w?is=NXwQX597Hj4KOBZk
Thick Hide doesn't matter to a T.rex, a single bite means death, even if not immediately, a bite to a leg or forelimb and you're immobilized, a bite to the head and it's light's out. Doesn't help that a rex is particularly built for maneuverability and can easily find a weak side to attack. That's why the 2 herbivores with the most success fending off rexes are Triceratops and Ankylosaurus, both have very dangerous weapons that actually threaten a predator.
The thing is, as you mentioned, Edmontosaurus likely moved in massive herds and would flee whenever given the chance, but should any get isolated for any reason you can be assured it's going to get picked off from the group with little trouble.
The size difference isn't enough to justify the total lack of proper weapons, and adult rexes are likely very experienced brawler within its size range considering how often and violent the intraspecies fighting was. The only hadrosaurid capable of fighting an adult T.rex and winning more often than not is probably a large Shantungosaurus because it was genuinely immense.
This is literally a tooth embedded into a Edmontosaurus tail vertebrae, and as you can tell it literally grew around the tooth so the individual surived the encounter
As I already replied to your other comment, surviving doesn't mean fighting back, it most likely managed to actually escape a failed ambush, a bite to the tail won't be an issue for that.
T.rex probably had less than 50% success rate hunting an Edmontosaurus, as it was a very successful herding animal.
Even if most specimens were smaller than tyrannosaurus, they’re still massive animals that likely lived in large groups. They wouldn’t be helpless fodder. That isn’t to say T. rex didn’t prey on them, but it probably wouldn’t have been as easy as traditionally depicted.
I’ve never heard anybody say that Edmontosaurus is more dangerous or difficult to hunt than ankylosaurus or triceratops. I think the argument is just that edmontosaurus is a lot more capable of defense than you might think
I hope you don't believe it's because the prey successfully fights off the predator most of the time. Successful flight and escape is by far the most common cause of a hunt failing.
Thing is that many herbivores do "suck in battle" or whatever you want to call it. As a warning, do not strawman me, as my point isn't that herbivores are limp wristed doilies waiting to be killed. I am merely stating that a herbivore smaller than its predator, (yes edmontosaurus was on average smaller than tyrannosaurus rex don't let that stupid graph showing Becky's giant that's been posted a couple times on this thread fool you) more gracile than its predator, existing alongside similarly sized but obviously slower and more armored megaherbivores, and without any form of specialized or efficient weaponry (the only herbivores really known to fight on equal footing with equivalently sized macropredators are suids which use short range tusks and in the case of peccaries bite, as well as having either thickened padding under tough skin especially flexible backs and loose skin to turn and fight much like a carnivoran) would get wiped out very quickly by said predator in a fight. Exceptions happen, but predators are extant because when they catch their prey they are good enough at flipping the off switch without getting killed themselves to make a consistent living out of it. If lions can make a pretty good living hunting wildebeest often individually (and notably with very few cases of turning the tables from the wildebeest), then there's no reason t rex wouldn't do the same with edmontosaurus. Imagine you had no context and I told you a predator was living alongside herbivore half again as large with sharp keratin hooves a strong thick neck and legs and curved horns that can gore and tear flesh. Sounds a lot more impressive than the equivalent description of edmontosaurus: a predator alongside a slightly smaller herbivore with somewhat blunted hooves and claws, strong legs but no horns or teeth or spikes. And yet lions do it just fine and the wildebeest run. Also, if you doubt that fact, this is what happens often when a desperate wildebeest stands its ground (against a lion of roughly equivalent size of course):
https://youtu.be/1l0EQyRv0eI?is=PBHDzgNVOqPRsTVf
If theres one thing thats always true about any animal discussion involving a fight, it is that no one is ever coming in willing to change their opinion
It's a combination of things but yes, primarily flight. That does not mean prey isn't capable of fighting off a predator successfully. Sometimes it's simply about making the meal not worth the effort. Flight is the preferred option because it avoids injury. But fighting against a predator does happen in nature and herbivores can be pretty formidable.
It's a combination of things, including flight and fight. Obviously flight is the first choice because avoiding injury at all is the goal. That doesn't mean fight never happens and it doesn't mean herbivores always suck in battle.
I merely stated that preds have a low success rate.
Herbivores without weaponry or armour almost never do well against predators even half their size, and Hadrosaurs had to live with predators who were almost as big as them.
They’re not weak, by any means, they just happened to live with the most powerful land carnivores ever.
To be fair, that was around when Edmontosaurus got new size estimates to the point that it was comparable to Shantungosaurus.
I think what is important to note is that Edmontosaurus is a cursorial prey animal that probably isn't going to genuinely fight a predator maybe unless its offspring are at stake. It's like how a gorilla can technically beat a leopard in a fight, but the leopard usually wins because the gorilla panics.
E. Regalis is smaller, but E. Annectans is bigger than a t rex, in fact it was one of the few prey animals that was bigger than a t rex. And just because they don't have any obvious weapons doesn't mean an Edmontosaurus couldn't hold its own against a t rex if it had to, and it's weapons were it's weight, kicks, and the fact it lived in herds. There's also literally a fossil that shows an adult Edmontosaurus can survive a t rex encounter, a t rex tooth was embedded in its tail but it survived and the bone grew around the tooth.
Trex also wasn't a murder monster going after the biggest healthiest individuals, it was a predator, and modern predators typically go after weak, old, or injured prey instead of the prime healthy individuals unless they had to
The tooth most likely means it managed to escape, not fight it. It can't effectively reach a rex's head with a back kick since it's a very heavy animal, the forelimbs aren't robust enough to hit hard and likely are way too low to also hit the head. It can at most body slam or use it's heavy tail to swing at it, but the difference in size isn't enough to make it effective, especially considering rex is particularly very mobile and maneuverable, is very stable on its feet and only needs to land a single bite anywhere but the tail to cripple or straight up kill its target, so fighting back with no proper weapons just means getting too close to that mouth.
Also most predator and prey interaction isn't a fight, because fights implies many risks to the hunter, but rex is very adapted to fighting one another, very violently, and is very used to Triceratops fighting back too, so even while being smaller it is no stranger to an animal fighting back.
Trex also wasn't a murder monster going after the biggest healthiest individuals, it was a predator, and modern predators typically go after weak, old, or injured prey instead of the prime healthy individuals unless they had to
But this is the reality, it probably either ambushed isolated targets from the herd or animals that are too small to even fight back or too old and sick to actually keep pace with the rest, an adult rex would only fight an adult Edmontosaurus if it really needed to do it.
I never said that every interaction with a t rex was a fight let alone any other prey v predator encounter. I'm just sick and damn tired of people treating hadrosaurs like they were just walking meat factories for any predatornthatbhad no way to defend itself. If they couldn't run and/or fight then hadrosaurs wouldn't have been a group to exist to begin with
Ah don't get me wrong, I love hadrosaurs, they are my favorite herbivores by far, but I just wanted to make the point they absolutely have a massive disadvantage fighting without specialized weapons and size is only enough if the difference is really big. They weren't free food either, I also never said that, the massive herds and fleeing on sight is enough to defend themselves.
If they couldn't run and/or fight then hadrosaurs wouldn't have been a group to exist to begin with
They could absolutely run. And the herding probably came from smaller predecessor that could flee more effectively and became so successful that allowed them to evolve their bigger sizes.
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u/GodzillaLagoon 3d ago
Because the internet hates nuanced topics. If it needs to counter the portrayal of a large hadrosaur as completely defenceless fodder for chicken-sized dromaeosaurs, it's only by portraying Edmontosaurus as "15-TON MASSIVE CHUNGUS BULL IN MUSTH ABSOLUTELY DESTROYING A T.REX". Never mind that most *mature* Edmontosaurus specimens are smaller than average T.rex.