T. rex Bite Pressure

[Dinwar]

Here's a fun Science Daily news article about my favorite predator. They're arguing that the T. rex had the most powerful bite pressure of any animal.

This is...interesting. It's certainly not unexpected. Other studies have shown that predator to prey ratios in unimpacted ecosystems are much higher than we typically think, based on studies of osteophagy (basically, eating the bones) and tooth wear. While I'm sure that an ecosystem based on a lizard-dominated megafauna will have some differences from a mammal-dominated megafauna, the idea that carnivores were a fairly hungry bunch is probably accurate. Which means that it's likely that carnivores ate a variety of low-quality foods, such as bones. I never imagined that anything, T. rex or otherwise, was chomping on an Apatosaurus femur, but some of the smaller bones, and bones of smaller critters, likely got chomped up. This study seeems to support that.

There are a few issues, however.

Originally Posted by article

The team artificially scaled up the skulls of a human, alligator, a juvenile T. rex, and Allosaurus to the size of an adult T. rex. In each case the bite forces increased as expected, but they did not increase to the level of the adult T. rex, suggesting that it had the most powerful bite of any terrestrial animal.

This hurt. Simply put, you cannot simply make animals bigger and expect it to work out properly. Bones and muscles don't scale that way. And I'm confused as to why they're scaling up to begin with. My dog's bite is somewhere in the 200 psi range. Mine is not. Our skulls aren't the same size, but when he's gnawing on your arm the point is purely academic--250 psi is 250 psi.

Quote:

An animal's bite force is largely determined by the size of the jaw muscles.

Not quite. This is part of it, yes--however, most critters do not enjoy biting so hard they snap their jaws. This is actually a bigger issue than it sounds like: polar bears, for example, actually have fairly weak jaws for just this reason. One way to analyze this is finite element analysis, which is used by engineers to find stress points. If the stresses exceed the strength of the material, the material breaks--and if your jaw is busted it doesn't matter how powerful your muscles are, you don't eat. I've yet to hear of a good way to deal with the fact that teeth are separate from the jaw, however. Not so critical with predators, but with equids and camels it's problematic (they have less jaw under the teeth roots to absorb the stress).

Quote:

The large difference between the two measurements, despite the error margins factored in, may suggest that T. rex underwent a change in feeding behaviour as it grew.

This is interesting, and suggests (to me, anyway) some active parenting. What I mean is, the adults could be letting the young eat first at the kill, like dholes apparently do. If someone gives you something to eat, you don't start with the hard parts--you eat the tasty squishy stuff first. Then the parents eat the more crunchy bits, requiring a stronger jaw. The increased strength of the jaw may be a developmental factor (similar to our own wisdom teeth), or it could simply be that T. rexes eat more bone as they age and their jaws get stronger because of that. Of course, that's all speculation--I'd appreciate any thoughts any biologists who study modern predator behavior might have!

Originally Posted by Dr Karl Bates

"Our results show that the T. rex had an extremely powerful bite, making it one of the most dangerous predators to have roamed our planet. Its unique musculoskeletal system will continue to fascinate scientists for years to come."

~sigh~ This is so far from true that it's remarkable someoen with a Ph.D. said it. Again, my dog has a much stronger bite than I do--but I'm the more dangerous predator, thanks to my rifle. Dogs hardly have the greatest bite pressure, but they're among the more successful predators thanks to their pack behavior. Smilodon fatalis couldn't even bite its prey to kill it (the teeth got in the way), yet that skull morphology was independantly derived in multiple lineages, a pretty clear sign that it works. Nutcracker man had a powerful bite, but was apparently a herbivore--hardly a dangerous predator! Bite pressure likely has much less to do with killing power than it does with feeding behavior. Simply put, if you don't bite the hard parts there's no reason to develop powerful jaws--and if you do, it's not necessarily because that's how you kill the animal.

It's an interesting study, and I'm going to have to find the real paper to look at it--obviously any news report will be distorted. And it's always exciting to find evidence, however tenuous, of family behavior in the rock record. That said, this study has some pretty big holes in it if the reporting is even half-right, and further research should certainly be done.

[Modified]

Originally Posted by Dinwar

My dog's bite is somewhere in the 200 psi range.

Per square inch of what though? For a single sharp tooth biting down on something, the bite strength of your dog is initially probably hundreds of times higher than that. I suppose per square inch of total cross-sectional area at the base of each tooth might be meaningful.

[Stomatopoda]

There seems to be a big (an annoying) debate about whether T. rex was a predator or a scavenger. This strikes me as illogical, as no apex predator is above scavenging, and no scavenger is going to pass up an opportunistic kill.

[Lowpro]

Dinwar what's the projected masseter muscle size and bone density of the Trex jaw? That's what's going to determine their bite potential.

I don't know their bottom jaw density, but I thought that current Trex theory is that most Trex's were probably not scavengers because their skull density was higher indicating large muscles for mastication, which meant their food was probably not rotten.

But what do I know

[Marduk]

T Rex is a predator, I saw it in that movie, it has a bite pressure sufficient to eat a lawyer, surely thats enough

[Lowpro]

Originally Posted by Marduk

T Rex is a predator, I saw it in that movie, it has a bite pressure sufficient to eat a lawyer, surely thats enough

Well, lawyers are full of **** which means that extra bite pressure isn't too valuable

[rjh01]

One difference between a predator and a scavenger would be brain size. A predator must be able to out wit its prey. If it hunts in a pack then it needs a good brain in order to do so.

If there are a large number of prey animals per predator that means the predator is warm blooded. It needs to kill and eat a large number of animals in order to generate the heat required to live.

[OnlyTellsTruths]

Originally Posted by Stomatopoda

There seems to be a big (an annoying) debate about whether T. rex was a predator or a scavenger. This strikes me as illogical, as no apex predator is above scavenging, and no scavenger is going to pass up an opportunistic kill.

I believe usually, when there is an argument such as that, it is about whether or not the creature was mainly X or mainly Y. They assume it would of course do some of the other.

I agree with you that it would be illogical if they were arguing that it does X or Y exclusively.

[Correa Neto]

Sure, Cretaceous environment was different from anything we have nowadays; the best we can do are analogies and extrapolations, always knowing they will have flaws. But some hints can be found. I never managed to "get" the controversy on scavenging x predator T-rex, since no predator will let go the chance of eating a carcass. Easy food. Heck, nowdays lions fight hyenas for carcasses.

And this brings us to the tyrant king lizzard's bite... Seems a good chunk of the evidence used by those who defend it was a scavenger is about teeth morphology- good for piercing through bones. Sure, a powerful bite coupled with these teeth make sense when it comes down to piercing and breaking bones. Hey, look, just like hyenas! Hyenas will not decline an invitation to lunch a carcass and also are active fierce predators. Same with lions, leopards, jaguars, wolves, wolverines, white sharks, [add predator name here]. The difference? Hyenas can get more from the carcass, because they can process bones.

Now, add to this the interpretation on t-rex younglings jaws... A possible interpretation (maybe better label as extrapolation) built over it is that they may have been pack predators, not unlike like nowadays' hyenas and the older members would let the younger members feed first. Or maybe they just changed behavior (forming or not groups) according to size and age. Smaller animals went for meaty prey while larger ones would have to add a larger ammount of carcasses, lower-quality food, maybe to gather all the energy it would take to power such huge bodies. Given Cretaceous fauna, it seems a fairly large ammount of big carcasses would be around.

Sure, a look in to T-rexes coproliths may tell a lot about it all and prove my babble is just babble and I am way out of my league, deserving to be banned back to my cozy Archean ad Paleoproterozoic times.

Now, lets also remember that such adaptations would also be nice for handling prey with armour, and such herbivores were around in their times.

[Marduk]

Originally Posted by Correa Neto

Now, lets also remember that such adaptations would also be nice for handling prey with armour, and such herbivores were around in their times.

Prey such as this Triceratops which was known to be eaten by a T Rex

Quote:

The 4 1/2-foot-long Triceratops pelvis had 58 definite bite marks and 22 probable bite marks that could only have been made by a T-rex, Erickson says. A cast of one of the punctures was an exact replica of the canine-like tooth of an adult Tyrannosaurus, and distinctive serrations like those on the cutting edges of T-rex teeth could be seen where the teeth had scraped the bone surface.

Quote:

The T-rex obviously gnawed the pelvis for a while, pulverizing the vertebrae and probably severing the pelvis from the body, according to Erickson.

of course this doesn't prove that the T Rex didn't scavenge the animal but

what are the odds of finding a dead immature Triceratops which was apparently untouched by any other predator and just sitting there pristine waiting for a TRex to pass by like a chicken waiting for me in the supermarket

Its not likely is it,

[Correa Neto]

Well, one of the keys here is the word "apparently"... The other is the context of where the pelvis was found (something I am not aware of). Taphonomic data is required. There are a number of circunstances where something like this (rex finding young triceratops carcass, untouched - or mostly untouched) could happen, and some can create a fossil record (or be preserved as).

A migrating herd crossing a river, with or without a flash flood is the first example that comes to my mind. Another possibility would be T-rexes following migrating herds. Weaker specimens will die (old, sick, young) and are eventually left behind. Rexes would just have to wait. A rex could also steal a fresh kill from a smaller predator, one of those whose teeth were more adapted to slice flesh, with smaller odds of leaving bite marks in the bones.

Or a rex could have been the one who made the kill.

Without taphonomic data, its mostly a guess.

But one thing I can tell you- if rexes were still around, outdoor activities as a whole would be much more... Uhm... Exciting, to say the least. Sure, if the big ones had feathers, as at least one reconstruction I saw, they would be ridiculous. Dangerous but ridiculous.

[Big Les]

Originally Posted by Dinwar

While I'm sure that an ecosystem based on a lizard-dominated megafauna will have some differences from a mammal-dominated megafauna, the idea that carnivores were a fairly hungry bunch is probably accurate.

Minor point, but dinosaurs aren't lizards, despite their 'terrible lizard' moniker.

You did have the correct abbreviation though ('T. rex'), 'T. Rex' of course being a rock band, and Trex a type of lard.

[Dinwar]

Originally Posted by Correa Neto

The other is the context of where the pelvis was found (something I am not aware of). Taphonomic data is required.

Sadly, this is missing in many, many cases. There's a locally famous work by George T. Jefferson called "A Catalogue of Late Quaternary Vertebrates from California". Got my hands on Part 2 (mammals) about 6 months ago. It illustrates the problemw quite well--all it provides is a locality name, species list, and sometimes an age range. If you're really luck the formation name will be included. That is, sadly, considered good data to many paleontologists.

Originally Posted by Marduk

what are the odds of finding a dead immature Triceratops which was apparently untouched by any other predator and just sitting there pristine waiting for a TRex to pass by like a chicken waiting for me in the supermarket

Well, there's no real way to prove that with the data paleontologists have on hand. It's speculated that saber-toothed cats used their iconic teeth to pierce the throats of animals. That sort of attack won't leave much in the fossil record--while I've seen a few dino necks, they're quite rare and never, to my knowledge, has skin been found associated with a kill site (though I'd love to have someone point me to one!). So it's entirely plausible that some smaller critter took out the Triceratops, and the T. rex scattered them. The lion/hiena comparison again springs to mind--if a hiena kills something, a lion won't have any problem taking that kill.

Originally Posted by Lowpro

Dinwar what's the projected masseter muscle size and bone density of the Trex jaw? That's what's going to determine their bite potential.

You know, I really should have looked that up last night. I'm not sure their bite potential is going to be too informative about their killing potential, though. An uncle of mine used to raise emus (got too expensive after a while), and one got out once. One of the guys helping him get it back in the barn grabbed it by the neck. My first question was "When's the funeral?" That thing kicked him right in the gut, and only some pretty fast reflexes saved the guy's life--as it was, he had a pretty nasty flesh wound. Sure, an emu bite hurts--but it's not the bite that kills you, it's the kick. Emus are basically therapods that lost their tails, so it's not entirely unreasonable to think that other therapods had similar killing styles. Dynonechus, Veloceraptor, Utahraptor, et al. seem to have done so (unless you believe they used those claws for tree climbing, a notion I find silly). I'm not sure a T. rex would evicerate its prey with its feet (that's a LOT of animal to stand on one foot, and a lot of power to ballance while doing so), but it serves to illustrate my point that bite pressure alone isn't sufficient for determining killing power.

ETA:

Originally Posted by Big Les

Minor point, but dinosaurs aren't lizards, despite their 'terrible lizard' moniker.

True. In fact, nothing is--"lizard" is a polyphyletic grouping, which in taxonomic terms means it has the same validity as, say, maya spirits and balrogs. (And if you REALLY want to have fun, look at paraphyletic groupings, particularly as they apply to the fossil record!) Should have used "reptile".

[Dinwar]

I got ahold of the original paper! (As an aside, anyone who likes this type of thing needs to join Academia.edu--it's a fantastic way to get get papers, discuss with scientists, etc). Turns out they did just look at the skull as a single, unified piece, without determining where stress points would occur. That said, they have the necessary data, it would appear--shouldn't be too hard to run.

To answer the question of the squishy bits, they used the adductor mandibulae externus group, adductor mandibulae posterior group, and the pterygoideus group. Used a range of values for the size of those muscles.

My question now is, how do you account for the fact that a T. rex's teeth aren't even? You're not going to have a single line of teeth hitting something--a bite would be more of a series of puncture wounds. It'd likely do more damage, as each tooth would pierce the flesh independantly, preventing the bed-of-nails effect.

My earlier arguments about the relationship between bite strength and predation/scavanging still hold true--they assumed that high bite force=predation and low bite force=scavanging.

I really need to look into modern predators and scavangers....I'd love to be able to prove that this relationship is entirely fictitious.

[Lowpro]

Well other factors such as neck strength and snout length may also give hints too. "beakier" snouts may imply scavenging as to stick their snouts within a corpse rather than rend it, and may also account for lower neck strength (same things they've determined with condors and buzzards).

As for uneven dentition...iunno. I like the idea of removing the "bed of nails" thing, haven't thought of that before or heard it. I don't know the relationship of bite force to mastication though, and I don't think Trex's did much chewing because they don't have any teeth to do it, so maybe it's more like how a crocodile uses its teeth for "grabbing and killing" and then just crushing the meat like a meathammer with its palate.

[Toontown]

If I were a scavenger, and I could bite like a T Rex, you damn well better not let me get my jaws on you. I will chase your ass down if I can, scavenger or not.

We know they weren't particularly averse to combat. The largest T Rex ever found was a very large female that was apparently killed by another T Rex. The murderer bit partially through the top of her skull. The bite then proceeded down through her eye socket, scraped down the side of her skull, hooked onto her lower jaw, and pulled it off.

So, they could bite good and pull hard. Not to be taken lightly. When T Rex come, you step aside. Lot of big-ass muthers didn't, and a lot of big-ass muthers died.

But they probably were primarily scavengers. They probably scavenged the same way the short-faced bear did. By driving bad-ass predators off their kills, or eating them too if they wouldn't go.

They may not have been particularly concerned about being injured, which would have made them doubly dangerous. They apparently operated in groups of two or more, and would apparently care for injured members of the group. Case in point: the above-mentioned large female had fully recovered from a broken femur. There was no way she could have survived that without help.

[Dinwar]

That's certainly one idea. Personally, I've always liked the idea of them following the hadrosaur herds. Though I admit that it's for non-scientific reasons--it's extremely similar to some ideas of how humans behaved, though our prey extended a bit further.

Originally Posted by Toontown

They may not have been particularly concerned about being injured, which would have made them doubly dangerous.

I wonder....I've always found mammology's focus on skulls and teeth annoying, and we really don't have good studies of postcranial anatomy. The issue is, I'm wondering if it's that the T. rexes didn't care about being hurt, or if they didn't have a choice. I know there were cats and dire wolves with abscessed teeth, a horrifyingly painful injury that they lived with for some time. I'll grant you, the healed fracture is certainly proof that they helped one another, but hunger will drive one to desperation very quickly.

Originally Posted by Lowpro

Well other factors such as neck strength and snout length may also give hints too. "beakier" snouts may imply scavenging as to stick their snouts within a corpse rather than rend it, and may also account for lower neck strength (same things they've determined with condors and buzzards).

I'm hesitant to over-extend that, though. Dogs have longer snouts than bears, and crocodilians are all predators. All our interpretations are going to be dependent upon how we assume these things killed their prey, IF they killed prey.

[Lowpro]

Right but to be a bit nitpicky bears also have large forearms and extremely large muscles to use them.

Trex's pretty much have their legs, head, and maybe their tail as far as any tactile use is concerned. With lizards, the head and jaw reflect their diet a LOT and a Trex's head grows a LOT as they age (if you've seen Trex fossils, their heads grow a LOT compared to their whole body) so I wouldn't be surprised if they were scavengers or at least ate entrails as adults, OR their bite may be more related to them using their palate and not their teeth to crush and consume food; perhaps a lot of both.

In the context of their evolutionary pattern I think it's sensible to conclude that their snouts, being elongated, indicates that they were "snag and crush" more than "rip and tear"

A lot of that has to do wish assuming that their masseter muscles were pretty damn large and dense, but I don't know if the fossils found have any tuberosities that were maintained to give a good glimpse. I wonder how often anatomists are called in to develop ideas on it.

Also...dogs have molars, Trex's dont as don't most reptiles.

[Dinwar]

Originally Posted by Lowpro

Also...dogs have molars, Trex's dont as don't most reptiles.

Not as true as most believe. I mean yes, the teeth aren't molars, but they do have heterodont dentation--the front teeth are very pencil-like, and clearly not good for biting/crushing, while the back are much more suited to such uses. To me, it's one of the most striking things about the animal (after the tiny arms and the ridiculous size). So there was some differentiation of the teeth, though not nearly as pronounced as in mammals (good thing, too--could you imagine what paleontology would be like if dinosaur anatomy was limited to skulls and teeth?!).

Quote:

A lot of that has to do wish assuming that their masseter muscles were pretty damn large and dense, but I don't know if the fossils found have any tuberosities that were maintained to give a good glimpse.

Well, Tyrannosauroidea has produced a number of well-preserved skulls, likely due to their size and sheer bulk. Not sure about the tuberosities--the book on dino anatomy I have doesn't really get into that.

It does, however, state that tyrannosaurid teeth catch meat particles in their serrations. I remember reading something about that in college, but I never saw any corroboration--it's what convinced me they were predators, since there's no reason for a scavenger to have an infectious bite. It also states "However, a 44-cm long coprolite from the Scollard Formation probably referable to T. rex (based on the size of the element and the known size distribution of the carnivorous members of the fauna) contains a high proportion (30%-50%) of macerated ornithischian bone fragments by volume (Chin et al. 1998)." For an ichnofossil that's actually fairly good evidence--most of the time it's "Oh look, an animal made this. Probably a worm. Of some sort. Maybe." The authors also list a number of likely T. rex bites where the prey survived, based on the size of the puncture wounds and the local fauna of that formation.

Quote:

In the context of their evolutionary pattern I think it's sensible to conclude that their snouts, being elongated, indicates that they were "snag and crush" more than "rip and tear"

In part, yeah, I'll agree with you...With two caveats. Their snout isn't that elongate for a therapod (look at the raptors on Jurassic Park sometime--while it's dated, they got the anatomy [other than size] fairly accurate). Second, after they've crushed it I think they used their maxilary teeth to scrape the meat off the bones. I've seen my dog do this--when we eat at a certain Thai restaurant (honestly, they like the dog better than they like us--they bring his drink first and know his order as soon as they see us) we order the dog chicken on a stick, and he always grabs the meat with his front teeth and pulls. It's not terribly difficult to imagine a T. rex doing the same thing, if they have the time--and if not, crunch it up and gulp it down. What I'm envisioning is the T. rex using the power of its jaws to bring the prey down quickly with minimal fuss (as time spent killing the prey increases, so does the likelyhood of the prey killing the predator), simply due to the overpowering trauma. The T. rex can survive, because it constantly replaces teeth and has pretty flexible teeth at any rate, and the power of the jaw muscle means they can strike more or less anywhere on the prey's body. If it fails, odds are the prey will become infected, allowing the predator to pick it off later. Both would be very well suited for ambush-style predation, or at any rate extremely quick attacks. Then, once they killed the prey (well, let's be honest--once they got it to the point where it's not struggling enough to bother the T. rex anymore), they use their front teeth to eat the higher-nutrient material, or strip it for the young to eat.

My wife is concerned. It's late, and I'm still up looking at T. rex skulls.

[Roboramma]

Originally Posted by Dinwar

ETA: True. In fact, nothing is--"lizard" is a polyphyletic grouping, which in taxonomic terms means it has the same validity as, say, maya spirits and balrogs.

I think you're going a little far there. I could agree that the term "lizard" has no real biological significance, but it's still a word that refers to a grouping of real animals. Similarly if my girlfriend and I wanted to get a dog and she said "Make sure it's a black dog", I wouldn't say "there's no such thing", in spite of the fact that there's no biological significance to the group "black dogs". The same is true if she said "I want a pet lizard". I would know what she wanted and wouldn't bring home a snake.

Similarly, fish are fish, and people find the word useful. The fact that some fish are more closely related to me than they are to other fish doesn't change that fact.

[GlennB]

I'm a bit worried about the difference between force and pressure here.

Over in the Quiz thread someone asked about the greatest bite pressure of any living animal (iirc the answer was the crocodile or alligator). I opted for the gerbil Get bitten by one of those monsters and it'll slice through your flesh like a scalpel. Meanwhile beavers can chew down trees through the pressure their teeth exert, while a croc would probably be there forever even if it really wanted that tree felled.

Meanhile ... did T Rex get respect?

[Correa Neto]

On the snouts of the tyrant gecko...

http://www.sciencedaily.com/releases...0518105742.htm

TLDR?
Here's the short version: Very strong, probably made the dismembering/crushing job easier.

[Damien Evans]

Originally Posted by Dinwar

Here's a fun Science Daily news article about my favorite predator. They're arguing that the T. rex had the most powerful bite pressure of any animal.

This is...interesting. It's certainly not unexpected. Other studies have shown that predator to prey ratios in unimpacted ecosystems are much higher than we typically think, based on studies of osteophagy (basically, eating the bones) and tooth wear. While I'm sure that an ecosystem based on a lizard-dominated megafauna will have some differences from a mammal-dominated megafauna, the idea that carnivores were a fairly hungry bunch is probably accurate. Which means that it's likely that carnivores ate a variety of low-quality foods, such as bones. I never imagined that anything, T. rex or otherwise, was chomping on an Apatosaurus femur, but some of the smaller bones, and bones of smaller critters, likely got chomped up. This study seeems to support that.

rest snipped

The Mesozoic was in no way a lizard dominated era. If you must compare it to something modern, it would be Birds or Crocodiles, not lizards, which live in vastly different ways to how Dinosaurs would have.

If you want a look at a lizard dominated area lot at pre-human Australia. Sure there was Thylacoleo, the Thylacine and the Tasmanian Devil, but by far the largest predators in the land were Varanus Priscus, better known as Megalania, a giant monitor lizard, the 5-6 metre long Wonambia, the various pythons of the genus Morelia, the various Elapid snakes and of course the extant monitor lizards, particularly the Perentie and the Lace Monitor, and the now extinct in Australia Komodo Dragon. Yes I cheated and included snakes there but they're a lot closer to lizards than dinosaurs are anyway.

Incidentally, muscle studies have shown that, pound for pound, Thylacoleo had the strongest bite of any mammal so far discovered.*

*Wroe, S., McHenry, C., Thomason, J. (2005) Bite club: comparative bite force in big biting mammals and the prediction of predatory behaviour in fossil taxa, Proceedings of the Royal Society 272, p. 619-625

[Dinwar]

Originally Posted by Roboramma

I think you're going a little far there. I could agree that the term "lizard" has no real biological significance, but it's still a word that refers to a grouping of real animals.

Not at all--I'm just being pedantic. Polyphyletic groups have no biological reality, and are therefore not in any sense of the word real. They're based on real organisms, but the grouping itself is fictional. Paraphyletic groups (a taxa and most of its decendants) have some validity, particularly in paleontology--otherwise every time we talk about "fish" we'd have to include all terrestrial vertebrates. But paraphyletic groupings are a bit sloppy and really amount to "this clade except those things over there". The only real biological grouping is the monophyletic group: a taxa and all the disendant taxa.

It's one of those things that I really should know better than to say. Typically I do--it's just that in this case I wasn't overly interested in taxonomy, but rather morphology, and got sloppy.

As far as people finding the grouping useful, that's not really the point. Many fictions are useful--there's a whole theory that religion is one of these, for example. Another is the Bhor model of the atom, or the fence-post model of polarization. They're useful, but when someone (rightly) calls me out for using one I'll correct myself.

Originally Posted by Damien Evans

The Mesozoic was in no way a lizard dominated era. If you must compare it to something modern, it would be Birds or Crocodiles, not lizards, which live in vastly different ways to how Dinosaurs would have.

Again, the point is well taken; it's a bit beside my point, however. No matter what you call them, a dinosaur-dominated world is different from a mammal-dominated one, and this can easily include predator/prey ratios. I'd also be hesitant to call it a crocodile-dominated world. Crocs were MUCH more diverse in the Mesozoic, including forms that make the Daedra in The Elder Scrolls games look downright normal; however, I don't believe that they were dominant in the Campanian/Maastrichtian, when the T. rex was. My impression was that they were more Triassic; at any rate, I don't know of any from the areas T. rex has been found. Birds is the closest, but I'd be hesitant to say too much on that count--too much time has passed. That said, emus do offer a great opportunity to ground-truth this calculation.

[Correa Neto]

I'll keep calling them fat overgrown (feathered?) geckos. They never complained.

[luchog]

Originally Posted by Dinwar

I got ahold of the original paper! (As an aside, anyone who likes this type of thing needs to join Academia.edu--it's a fantastic way to get get papers, discuss with scientists, etc). Turns out they did just look at the skull as a single, unified piece, without determining where stress points would occur. That said, they have the necessary data, it would appear--shouldn't be too hard to run.

To answer the question of the squishy bits, they used the adductor mandibulae externus group, adductor mandibulae posterior group, and the pterygoideus group. Used a range of values for the size of those muscles.

One thing I don't know if they took into account, which I learned watching some documentaries on crocodilians, is the placement of the muscles with regard to bone strength. The Saltwater Crocodile has a bite force easily strong enough to break it's own lower jawbone. However, it also has one muscle group dedicated entirely to reinforcing the jaw, and distributing the force to prevent it from breaking.

[Mr. Purple]

Originally Posted by rjh01

A predator must be able to out wit its prey. If it hunts in a pack then it needs a good brain in order to do so.

Disagree. Snakes (and many lizards) are definitely less intelligent than the rodents and birds they prey upon.

[Dinwar]

Originally Posted by luchog

One thing I don't know if they took into account, which I learned watching some documentaries on crocodilians, is the placement of the muscles with regard to bone strength.

No mention of it--they just went with the power of the closing muscles and the shape of the jaw. I guess they assumed infinite jaw strength (or, which amounts to the same thing, that the jaw had evolved to handle whatever the closing strength of the muscles was).

Originally Posted by Mr. Purple

Disagree. Snakes (and many lizards) are definitely less intelligent than the rodents and birds they prey upon.

I'm hesitant to go down that particular rathole. The issue is, how does one define intelligence? Plus, many organisms are sessile and predatory--hard to outwit your prey when you don't/can't move. And it doesn't take much intelligence to find a game trail and wait there until something tasty walks by.

Is there any way to estimate the amount of damage a bite would do? Not just strength, though that'd be part of it....What I'm thinking is that a T. rex would ambush prey, using its powerful jaws to simply do so much damage to the prey that it'd shut down (sort of like what happens when an organ is stabbed, or you hit something with a shotgun). Raw power would obviously help--you can do more damage if you can break bone--but that's certainly not the only way to do it.

I'd still love to see a finite element analysis of a T. rex skull--see where the stress points are and how much stress they'd be under. I think that, combined with the jaw strength, would go a long way towards explaining how they ate.

Another question is how strongly their jaws were fixed in their skulls. In mammals it's the condoil process that determines this--a wolverine has a very pronounced condoil process that more or less locks the jaw in its mouth, to the point where after maceration you can't take the jaw off without breaking either the jaw or the skull. In rabbits the process is so reduced that it's often difficult to identify where the stupid thing is. Wolverines have an extremely powerful bite (most wolverine skulls have broken teeth from where they were making good headway gnawing through the steel traps they were caught in), while rabbits have jaws built for chewing. The thing is, one of the iconic differences between mammals and reptiles/avis is the jaw structure. I'm not sure how to determine how well a reptile jaw is seated in the skull, or what role that plays in feeding behviors.

[GlennB]

Originally Posted by rjh01

A predator must be able to out wit its prey. If it hunts in a pack then it needs a good brain in order to do so.

Not really, it just needs technique. And technique can be an evolved skill.

Brain not necessarily required.

[Dinwar]

Come to that, not even cerebrial ganglia are required. A neural net suffices for one of the more successful predatory groups (Hydrozoa, I think--jellyfish, anyway).

[azzthom]

Any discussion of intelligence in predators should include Portia spiders. They have tiny "brains", yet they have displayed problem solving intelligence in hunting other spiders, some of which are twice their size. They even change their plan of attack if the current plan is not working. A massive brain is certainly not required.

To get to the point, intelligence in a predator is not as easy to gauge as some people may think.

As for T-Rex, my own guess is that he occupied a similar niche to the Hyena. Brave hunter if he needs to be, superb opportunist the rest of the time.

[Correa Neto]

So, the tyrant fat overgrown geckos ate carrion and live prey.

So did their minions.
http://www.bbc.co.uk/nature/17276531

[Dinwar]

I've been thinking about this, and I'm not sure I believe it's firm evidence that they ate carion. I mean, it could have been a wounded pterosaur, or a REALLY hungry pack of raptors. That said, scavanging certainly isn't unlikely--we're talking about pretty small animals, and even in packs I can imagine they weren't exactly the feared gods of death Jurassic Park made them out to be (Utahraptors, on the other hand....). Eating carion is almost certain for veloceraptors. I do have to wonder if a pterosaur tasted like fish, though.

We know that at least one member of that family ate live prey, though: the famous dinonychus and protoceratops fossil pretty clearly shows that.

[Correa Neto]

IIRC, at the article, the possibility of attacking a sick or injurired pterosaur was raised. They just think that eating a dead one was more likely.

Uh... The fighting dinosaurs fossil is not a velociraptor x protoceratops?

[Dinwar]

Sady, no. It's the veloceraptor's bigger cousin.

The LA Natural History Museum has a model of a veloceraptor skeleton next to a pelican and an archaeopteryx skeleton. They're all about the same size. I don't recall offhand (and my dino reference book isn't with me), but I think a protoceratops is the size of a large pig, up to the size of a small cow.