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26.08.2016 21:51 - How accurate is the Tyrannosaurus Rex from Jurassic Park
Автор: valentint Категория: Забавление   
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Последна промяна: 20.07 13:35


How accurate is the Tyrannosaurus Rex from Jurassic Park?

For the time, the T. rex in Jurassic Park was a decently accurate reconstruction of the animal.

But, time makes fools of all of us. And our knowledge of all dinosaurs and pterosaurs, especially T. rex has changed dramatically since the movie first aired.

Suffice to say, Jurassic Park got a few things wrong with the Tyrant Reptile King.

So in order to give an accurate look into the animal, how it lived, behaved and such, I feel the best thing to do is to summarize what we know of Tyrannosaurus rex, which is going to be a lot.

Fair warning, this is going to be a long answer, as T. rex is, by far, the most famous dinosaur, and the most studied extinct animal in existence due to a weird feedback loop.

That is, they do a lot of work on it, learning more things, which spawns other fields of study, so you learn more about it, which inspires people to get into paleontology, so you do more work on it.

And on and on it goes.

So, if you’re wanting a short answer of how accurate the T. rex is in Jurassic Park, the short answer is, some things are right, a lot of things are wrong, and that’s due to science always advancing as new evidence comes along.

So, this is my olive branch to the Jurassic Park fans.

I perfectly understand why the original author, and the filmmakers depicted the animal as it did.

However, this answer is asking if the depiction of the animal in Jurassic Park is accurate, so any time I criticize the movie, know that it’s technical reasons we’ve since discovered since the movie first aired.

So in that light, we will be splitting the answer up much like I did the last time I discussed Jurassic Park (which you can read here), just with a few considerations for T. rex’s sake. We’ll be dealing with the films’ claims about T. rex in order:

  • Overall Look: Where we look at how the films depict T. rex, and if it’s any close to reality. We’ll basically discuss its phylogenetics and closely related kin, if very briefly.
  • Hand Posture and Arm Function: Where we correct the films’ depiction of theropod hand posture, and especially T. rex’s hand posture. We’ll also discuss what T. rex might have used its puny arms for.
  • Eye Sight: Where we discuss if T. rex’s vision was really based on movement, or if it actually had exceptional eyesight.
  • Smell: Where we discuss T. rex’s sense of smell, as the films keep ignoring this.
  • Sound: Where we discuss the sounds that the animal could have made, based on what we know.
  • Speed: Where we discuss if T. rex really could run at 32 mph, and if it couldn’t, what speeds the animal’s biomechanics would have allowed for.
  • Predatory Ecology: Where we discuss T. rex’s predatory behavior, as well as scavenging behavior, and settle, once and for all, the predator vs. scavenger debate in this animal, as well as bite force and such.
  • T. rex Ontogeny: Where we discuss juvenile T. rexes, whether or not the juvenile T. rex of Lost World is accurate.
  • Social Behavior: Where we discuss the general social behavior between other members of species Tyrannosaurus rex, and if they were “good” parents in the general sense.

Like I said, this will be a long answer for what is, essentially, the most well-studied dinosaur in the whole of science.

So sit back, relax, pour a drink of your choice (mine’s 2 oz. of Ardbeg 10 Year Single Malt Scotch), and enjoy.

OVERALL LOOK:

The films depict Tyrannosaurus rex like this:

image

However, looking at the animal’s general size, how much flesh is on the face, and such, I don’t think this is a T. rex.

It seems more in line with a Tarbosaurus, which is a tyrannosaurid closely related to T. rex.

Why do I make this distinction?

Because T. rex, as a rule, is a rather freakishly overbuilt tyrannosaur.

The films’ depiction of the animal looks horribly shrink-wrapped, emaciated, and gracile compared to the famous brute that is T. rex.

Especially if you look at the skeleton of the creature.

image

This render of a T. rex skeleton by the people making the dinosaur simulation game, Saurian, was actually based on the specimen, Stan.

You may notice that the animal had gastralia, which is basically reverse ribs.

How do we know?

Because Sue, one of the most complete specimens of T. rex, had gastralia, and if one member of the species had this structure, phylogenetic bracketing makes a very strong case that all members of the species had this structure.

image

Here’s the mount of Sue at Chicago’s Field Museum. Notice the gastralia on her, and how the Saurian render is actually pretty bang on accurate to the animal’s actual skeleton

You’ll notice that even the animal’s skeletal structure is much more “chunky” than what you see in the Jurassic Park film franchise.

T. rex’s skeleton is, in fact, rather famous for how robust it is. It basically had huge, long, thick legs, a massive head with long teeth in it, a chunky torso, and in life, would have basically been HEAVILY MUSCULAR.

If we then put muscles on those bones, you can see that T. rex was basically all muscle.

image

Sure, this makes the animal look “fat” compared to the film, but you have to realize that I suspect that the filmmakers didn’t base their T. rex on an actual T. rex, or, if they did, they shrink-wrapped the thing into oblivion.

And because the animal looks thin and gracile, even in bone structure compared to the famous robustness of T. rex, I suspect the film’s “T. rex” is actually closer to another, similarly sized tyrannosaurid called Tarbosaurus bataar.

image

But even this render of an accurate Tarbosaurus isn’t shrink wrapped to oblivion like the T. rex is in the film.

“Okay, Colton, so what would T. rex look like if you put skin on those bones and muscle?”

Funny you should ask.

See, there was a debate on whether or not genus Tyrannosaurus was feathered or scaly.

Well, as it happens, Bell and colleagues actually found skin impressions of various tyrannosaurids, including Gorgosaurus, Daspletosaurus, and Tyrannosaurus, and concluded that these genera of large tyrannosaurids would have been covered in scales.

In terms of any feathering at all, the researchers concluded that if the animal had any, they’d be small, almost invisible down, and limited to the animals’ dorsal regions.

Here’s the paper itself for your perusal.

Tyrannosauroid integument reveals conflicting patterns of gigantism and feather evolution

“But Colton, there was a tyrannosaur discovered in Asia that was covered head to tail in feathers and was a similar size. So wouldn’t phylogenetic bracketing make a case that all tyrannosaurs were somewhat fluffy?”

Well, see, while phylogenetic bracketing is a useful tool, we have to remember that it is subject to actual fossil finds.

Further, Yutyrannus is indeed a tyrannosaur, but a tyrannosaur in a different lineage than Tyrannosaurus, which would be protoceratosaurids.

Animals that are more closely related like Gorgosaurus, Daspletosaurus, and Tarbosaurus show scaly skin.

So we can at least commend Jurassic Park for accurately predicting scaly skin for large tyrannosaurids.

However, while the film accurately depicted the skin, they also horribly shrink-wrapped the animal.

So our view of a T. rex is a robust, scaly covered brute that’s basically solid muscle.

Speaking of different lineages of tyrannosaurs, let’s go over tyrannosaur phylogeny pretty quickly.

Within clade tyrannosauroidea, which is characterized by having fused nasal bones, and small, D-shaped pre-maxillary teeth (teeth at the front of the mouth), both of which are the defining characteristics of a tyrannosaur, you have two basic divisions.

  • Protoceratosauridae, which are tyrannosauroids more basal than the other tyrannosauroids. These tyrannosaurs are notable for their fun crests.
  • Tyrannosauridae, which are the tyrannosauroids that are more derived.

Here’s a quick cladogram of the tyrannosauroid family tree, showing just how diverse tyrannosaurs really were.

image

We have basically everything from coyote sized members like

Guanlong:

image

And Dilong:

image

To brutes like Yutyrannus (which does have direct evidence of feathers):

image

Clear up to guys like

Daspletosaurus:

image

Albertosaurus:

image

And the awesomely named Lythronax, which means “Gore King” found in Utah:

image

And of course, Tyrannosaurus rex.

What about the film not depicting the animal with lips?

Well, lips on dinosaurs are a somewhat contentious topic, open for debate, especially for large tyrannosaurids.

One paper by Dr. Carr suggests that large tyrannosaurids wouldn’t have had lips, and have their teeth exposed.

A new tyrannosaur with evidence for anagenesis and crocodile-like facial sensory system

But an analysis of the paper by paleontologist Mark Witton suggests that Dr. Carr may have made an a priori assumption about crocodylian lips and the scales near them, so the animal still could have had extra-oral tissues.

Either way, both cases are very strong.

So I guess the film was kinda half right? We’d need more fossil evidence to say for sure.

The film also shows prominent hornlets above the animal’s eyes.

Is that based on any real science?

Yes, actually.

The previous paper I cited not only discussed the lip issue, but also noticed on other large tyrannosaurids that the top of their snouts had keratinized scales, and above the eyes, had keratinized hornlets.

Further, there’s interesting indications on the bones that heavily suggest that T. rex may have had ornamental scales on its snout, due to how closely the skin interacts with the bone in this region.

Here’s a video looking at that, specifically:

Rather interesting, if you ask me.

If we were to put flesh on our T. rex musculo-skeletal system, we’d have to go with scales, keratinized scales on the top of the snout, and keratinized hornlets above the eyes, and I’m actually willing to go either way on lip debate, as both aren’t necessarily wrong.

So let’s do that.

image

Here’s the completed design from the Saurian team, which was informed by Dr. Hartman, Dr. Carr, Dr. Hone, and Dr. Witton.

Here’s another by the Blue Rhino team for the Field Museum in Chicago, basically putting flesh on Sue and bringing her, somewhat to life:

image

And a full body shot:

image

Many people might start saying that T. rex now looks incredibly fat, but this is taking into account the animal’s skeletal structure, which is already amazingly robust, putting muscles on those bones, which is already going to make the animal look chunky, and then putting fat and skin on it.

This is why I said that T. rex, as it’s depicted in the Jurassic Park franchise doesn’t look like T. rex, which is famous for being big.

This view of the animal is much more in line with what we can see and infer from its skeletal structure. This was a large, powerful animal, that’s basically solid muscle.

Hell, lately, I’ve been calling T. rex the “Arnold Schwarzenegger” of tyrannosaurids, because it is such an outlier in all respects compared to its closely related kin.

Basically, depicting T. rex as thin and lithe is just inaccurate, and really betrays just how big and powerful this animal really was.

HAND POSTURE AND ARM FUNCTION:

Another thing that gripes me about the films’ depiction of T. rex is the hand position.

image

It shows the animal’s palms facing down, which science now knows that no theropod could have held that position without breaking the animal’s wrists, much less a Late Cretaceous, highly derived tyrannosaurid.

(PDF) Forelimb biomechanics of nonavian theropod dinosaurs in predation

The previous paper discusses the hand posture of non-avian theropod dinosaurs, and how they had to have held their palms facing each other.

So there is no way T. rex could have held such a position.

But all this talk of T. rex’s arms brings up a question.

What did it use its arms for?

The answer?

Not much.

See, if you look over the whole of tyrannosaur evolution, you see an overall increase in size, bulk, and power, and evidently, they didn’t use their arms for much, so they got reduced.

In fact, the species closely related to Tyrannosaurus rex, Tarbosaurus bataar, actually has proportionally the smallest arms in comparison to the rest of the body.

For example, T. rex’s arms are about 91 cm, but the whole creature is 12 meters long.

In Tarbosaurus bataar, its arms are an even smaller ratio, suggesting that Tarbosaurus may actually be a touch more derived than T. rex itself is.

Which is interesting to dinosaur nerds like myself.

That said the primary uses that the animal would have used its arms for were:

  • Holding on to struggling prey, as the arm bones show signs of repeated stresses, and the fact that computer modeling show that each arm could lift 199 kg, as suggested by this paper. Forelimb osteology and biomechanics of Tyrannosaurus rex
  • Helping itself to rise off of the ground, which was suggested by Henry Fairfield Osborn in 1906 after discovery of the animal’s arms.
  • Holding onto a mate, as suggested by Osborn as well.

In short, the animal’s main, primary weapon was its mouth and teeth, and considering how small the arms are, what they could have used them for was really not much at all.

Further, I believe the films may have hypertrophied the animal’s arms, as they should be smaller than that.

Just look at Saurian’s model and the model built by Blue Rhino studios, which were informed by actual tyrannosaur experts. They are puny.

Further, the films got the right number of digits, but incorrect sizes. T. rex’s first digit was smaller and faced more forwards than the second digit.

Here’s a T. rex arm for comparison:

image

So Jurassic World needed to fix and update their T. rex model to keep up with the science.

Speaking of other things the film got incorrect….

EYE SIGHT:

The films claim that Tyrannosaurus rex cannot see you unless you’re moving.

In this scene where Dr. Grant is talking about dromaeosaurid predatory ecology (which is also inaccurate, see my answer on the film’s depiction of Velociraptor here), Dr. Grant claims that T. rex’s vision is based on movement.

Now, he had no reason to make such an inaccurate point, and the genetic construct argument doesn’t make sense here, as this was before he heard of the park, and, Dr. Grant, as a paleontologist, should know that T. rex’s vision was actually exceptional.

This paper actually discusses the visual acuity of theropod dinosaurs, which of course, included Tyrannosaurus rex.

https://www.researchgate.net/publication/228671730_Binocular_vision_in_theropod_dinosaurs

To quote the study directly:

In summary, given (1) the strong correlation between (at least limited) binocular depth perception in those extant vertebrates possessing more than roughly 20є overlap (and full stereopsis in those vertebrates with about twice that amount), (2) the correlation between BFoV width and spatial ability (e.g., cursoriality), and (3) the extent of the remodeling of the cranium required to achieve a BFoV of 55є or greater, it would seem most parsimonious to conclude that the coelurosaurs included in this study all achieved functional stereopsis and all used that capability for spatially demanding tasks.

In particular, due to its great scale and broad frontal vision, Tyrannosaurus rex, of all sighted observers to have ever lived, might have experienced the most spectacular view of the three-dimensional world.

The study discusses in depth how good T. rex’s vision really was, and in short, its visual acuity was far higher than falcons, hawks, and eagles, which are famous for how sharp their eyes are.

And T. rex’s visual acuity was higher than their’s, I believe the paper says it was 16 times as good as a human’s, which surpasses hawks, eagles, and falcons, which, according to the paper, was around 3–4 times as strong as ours.

So, no Dr. Grant. This is an animal that had the sharpest eyes of any terrestrial animal, ever, and staying still would definitely be a poor strategy for survival.

It’d just look right back at you…

image

Further, there’s another problem that the films ignore…

SMELL:

T. rex had remarkable olfactory acuity as well.

So even if it didn’t spot you, which, as we now know is highly unlikely, it would have smelled you.

This paper discusses the olfactory acuity of large, carnivorous theropods, which of course includes T. rex.

Olfactory acuity in theropods: palaeobiological and evolutionary implications

The study concludes that tyrannosaurids, as well as dromaeosaurids relied on their sense of smell quite a lot, as evidenced from the larger than expected olfactory bulbs.

This suggests an animal that has a pretty damn good sense of smell.

So why didn’t the film show the T. rex sniffing out Dr. Grant and the kids? It perfectly had the sense of smell to do so.

I suspect that it was ignored.

In reality, if the animal couldn’t see you, which we now know that its vision was absolutely exceptional, it would have smelled you, meaning there’s not much you can do to avoid it seeing you or sniffing you out.

While I’m busy destroying your view of T. rex, I may as well destroy another iconic thing about this animal.

SOUND:

T. rex obviously roared, right?

I mean, it just makes complete sense!

Surely, it could have right?

…Right?

Well, unfortunately, there’s no evidence to suggest that T. rex could have roared.

This paper discusses the kind of sounds that they might have made.

Coos, booms, and hoots: The evolution of closed‐mouth vocal behavior in birds

The study looks at living archosaurs closely related to non-avian dinosaurs (birds and crocodiles), and concluded that T. rex did not communicate in roars, but in slightly less intimidating coos, hisses, and mumbles.

Think of an overgrown crocodile, and you have the right idea.

See, roaring is a form of communication, and cats of the clade pantheriformes are the animals famous for roaring.

T. rex, and its closely related kin, evidently lacked the necessary soft tissue structures in order to perform the roar.

If you want an idea of what the T. rex sounded like, think of sub-low mumbles like this video demonstrates:

Think sub-low, closed mouth vocalizations, sounding like an overgrown crocodile, and you have the right idea.

Which makes sense, we have direct evidence that it was a predator, and giving away your position by roaring before you attack is a great way to not be a successful predator.

So, despite its size, you might not even hear it coming for you….

SPEED:

“Well!” you exclaim, “I’m screwed if this predator decides to go after me, because it runs at 32 mph! I can’t outrun it!”

Well… you’re half right that you probably couldn’t have outran it, but wrong in the sense that T. rex could not run as fast as 32 mph.

This paper discusses the speed that T. rex probably could have ran at, and it’s between 15–20 mph, give or take.

A general scaling law reveals why the largest animals are not the fastest

But considering that speed, this paper also discusses that despite its size, T. rex was rather agile on its feet.

Lower rotational inertia and larger leg muscles indicate more rapid turns in tyrannosaurids than in other large theropods

“Well!” you say, “I definitely could have outran it!”

Sorry to say, these are normal sprinting speeds for us, and we get pretty tuckered out by constantly sprinting.

T. rex didn’t have this problem, because it could have held that speed for quite a considerable length of time due to the lovely named Arctometatarsalian Condition, which is fancy science speak for the middle metatarsal being squished between the other two metatarsals, improving the structure and rigidity of the foot.

Because that’s what it means, so for the sake of being succinct, we’ll call it an arctometatarsal.

So what is it referring to?

Well, let’s look at a mount of a closely related tyrannosaurid, Albertosaurus, which I took at a local dinosaur and pterosaur exhibit.

image

Look at the middle metatarsal. It’s being squished by the other two metatarsals.

Did T. rex have this structure?

You bet it did.

image

Why is this worth noting?

Well, this foot structure isn’t unique to tyrannosaurs, as this foot structure also showed up in other theropods that are known for either being long distance joggers, or sprinters.

But what does such a foot structure do?

Think about it, if you’re moving, your bones move, meaning you lose out on potential energy in each stride.

To be a strong runner in the dinosaur sense, you need nice long legs to increase the length of your stride, but also nice strong muscles to facilitate it.

Well, T. rex has both of those in spades.

Further, if you have this Artcometatarsalian Condition, this means that it acts as a shock absorber, allowing the animal to regain that energy on the next step, improving its speed.

Further, since we know that T. rex was also basically solid muscle, it also has a nice, big ol’ caudis femoralis muscle, which is the muscle that runs from the back of the thigh to the tail in theropod dinosaurs.

image

In essence, T. rex has the skeletal structure, and the muscular structure we’d expect it to have if it was chasing down prey.

“But it could only run 15–20 mph!” I hear you say, “It couldn’t have caught prey!”

But remember, dear reader, this is all relative. All a predator has to be is faster than the animals it preys upon.

Well, what did T. rex prey upon?

Edmontosaurus, a type of hadrosaur:

image

Triceratops, a type of ceratopsid:

image

(Before you ask about the bristles, that’s based on a basal ceratopsid that had bristles on its tail).

And Ankylosaurus, a type of ankylosaurid:

image

All of which are known to be slower than T. rex.

Basically, these were large, but slow moving herbivores.

Most tyrannosaurids seem to have favored juvenile hadrosaurs, so all it had to be was faster than them.

And its got the skeleton and muscles that allow for this, and evidently, the speed to do take them down.

All this talk of T. rex’s capabilities, based on what its biomechanics would allow for leaves us with a question.

“Was T. rex a scavenger or a predator?”

This is a perfect segue into the animal’s predatory ecology.

PREDATORY ECOLOGY:

Tyrannosaurus rex is one of the most freakishly overbuilt theropods known to science.

If we compare a similarly sized theropod to T. rex, Giganotosaurus, we can see just how freakishly overbuilt it is.

Here"s Giganotosaurus compared to Tyrannosaurus rex:

image

We have Giganotosaurus on the left along with the puny human for scale, with Tyrannosaurus rex on the right.

Even though the one on the left is a large, and powerful animal, it doesn"t have the frame that T. rex does, in all instances.

It doesn’t have the skull of T. rex, which compared to Giganotosaurus is basically solid bone, it doesn’t have the robustness of T. rex either.

Even if you just compare the skulls from a lateral view, it’s even more pronounced.

Here’s a picture comparing the skulls of Giganotosaurus and Tyrannosaurus rex:

image

T. rex’s skull is basically a massive lump of bone, pretty crazy for a diapsid skull, while Giganotosaurus’s skull is nowhere near as robust.

Combined along with that is the teeth. Tyrannosaurus teeth are in fact quite famous for being, well, large.

Here"s one of the teeth from the sides of the upper jaw:

image

Look at that! It"s basically almost solid bone, and it"s also almost cylindrical in shape, and it has thick, long roots.

Put that together, and this suggests an animal with enormous bite force. In fact, I believe it may be the strongest bite from any terrestrial carnivore, ever.

This paper discusses the relative bite forces of large theropods, and concludes that T. rex’s bite force is in the range of 18,014–34,522 N in a killing bite.

The Biomechanics Behind Extreme Osteophagy in Tyrannosaurus rex

To quote the study"s abstract, directly (which is free and open source!):

Most carnivorous mammals can pulverize skeletal elements by generating tooth pressures between occluding teeth that exceed cortical bone shear strength, thereby permitting access to marrow and phosphatic salts. Conversely, carnivorous reptiles have non-occluding dentitions that engender negligible bone damage during feeding. As a result, most reptilian predators can only consume bones in their entirety. Nevertheless, North American tyrannosaurids, including the giant (13 metres [m]) theropod dinosaur Tyrannosaurus rex stand out for habitually biting deeply into bones, pulverizing and digesting them. How this mammal-like capacity was possible, absent dental occlusion, is unknown. Here we analyzed T. rex feeding behaviour from trace evidence, estimated bite forces and tooth pressures, and studied tooth-bone contacts to provide the answer. We show that bone pulverization was made possible through a combination of: (1) prodigious bite forces (8,526–34,522 newtons [N]) and tooth pressures (718–2,974 megapascals [MPa]) promoting crack propagation in bones, (2) tooth form and dental arcade configurations that concentrated shear stresses, and (3) repetitive, localized biting. Collectively, these capacities and behaviors allowed T. rex to finely fragment bones and more fully exploit large dinosaur carcasses for sustenance relative to competing carnivores.

So yeah, in other words, T. rex could just bite right through the skin, through the muscle, through the bone, and just swallow all of that whole.

So yes, the film is right in showing that this animal could absolutely destroy a car.

All of this leads to an interesting question. Was T. rex a scavenger or a predator? This has been a debate I wish would be settled, but some people think that you can sustain a large carnivore by pure scavenging, despite the fact that the only pure scavengers are vultures, but, let"s settle this now.

The debate on whether or not Tyrannosaurus rex was a scavenger or a predator is one that I wish would be done with, as we have the fossils that point to what the animal was doing.

The answer?

It was a predator that occasionally scavenged, indeed like many other carnivores.

The notion that T. rex was an obligate scavenger is not one that’s generally accepted by tyrannosaur experts for several reasons, but I feel a demonstration of known predation events are in order.

This paper discusses the at present known predation events in Tyrannosaurus rex.

Physical evidence of predatory behavior in Tyrannosaurus rex

Then you start to see stuff like this:

image

That is part of a hadrosaur (duck-billed dinosaur) vertebrae. The pencil is pointing to something rather funny looking. In fact, what we"re looking at here is two vertebrae that have fused together as a result of a large carnivore attacking the hadrosaur.

The nice thing about tyrannosaur ecology is that for anything preying on the large herbivores, you often have tyrannosaurs as the largest carnivores in their ecosystems, followed by some dromaeosaurid. Since dromaeosaurids are quite a fair bit smaller than many large tyrannosaurids, it then makes sense that the dromaeosaurids aren’t feeding on the large herbivores, so you kinda already know who was the culprit.

Yep, that’d be the tyrannosaur.

What that is is a tyrannosaur tooth embedded into the vertebrae of this hadrosaur. It was a nasty wound, it survived, long enough for the bones to fuse and heal, with the bones growing around and over the tooth.

There"s another instance of a Triceratops horn being healed in a suspicious manner. See, Triceratops horns are a lot like a rhino"s, in that they can regrow. But why did this one regrow?

image image

There"s evidence of bite marks from T. rex on that horn. Apparently, T. rex bit it off, the Triceratops survived, which, is awesome, and the bones healed.

So we now know, for a fact, that these were predation events. Sure, they weren"t successful, but you"d be hard pressed to find another explanation for these that makes sense in the light of the fossil evidence.

So, did tyrannosaurs hunt? Yes. The fossils don"t lie, they"re right there in front of your face.

Now, is there any evidence for scavenging behavior in large tyrannosaurids, especially T. rex?

Yes, actually.

This paper by Dr. Hone and Dr. Watabi discuss a known scavenging event in Tarbosaurus, a similarly sized tyrannosaurid closely related to T. rex.

http://www.app.pan.pl/archive/published/app55/app20090133.pdf

The paper discusses a hadrosaur that"s known from an almost complete specimen with skin impressions even, and there"s loads of bite marks, where evidently, a tyrannosaur was using its front teeth to scrape meat off the bones.

They provide evidence that the hadrosaur had died somewhere else, its carcass was washed away by a flash flood, explaining the evidence of water damage. It was then buried with its arm sticking out of the ground, then a tyrannosaur got to it.

So we know it was a scavenging event.

In fact, one of the authors of that paper, Dr. Dave Hone, a tyrannosaur expert, explains it quite clearly:

Predation has long been in evidence for tyrannosaurs what with various healed bites and even teeth wedged into the bones of surviving meals. Certainly they tried to kill and eat living herbivores on occasion. But scavenging is by definition rather harder to generate.

In other words, what he"s saying is that that there are more fossils of predation events than scavenging events, because the conditions to generate a scavenging event, and having it show up in fossils is of course, harder to demonstrate, and even harder to find clear, conclusive fossils for.

The fact that his paper explains a known scavenging event is rather remarkable, given that argument.

This Triceratops hip is also evidence of a known scavenging event.

image

This is the bottom of a sacrum of a Triceratops. The arrows are pointing to several suspicious bite marks. Suspicious as though there were five or six large and powerful bitey things have knocked a hole in the hip and tore it apart.

In other words, Tyrannosaurus rex could not have been a pure scavenger. You don"t maintain a large 8 ton carnivore on pure scavenging, because the only other thing that could have killed the prey that it evidently fed upon, hadrosaurs, ankylosaurs, and ceratopsids, all of which are large, powerful animals, could only be, by definition, another tyrannosaur.

Further, there is direct evidence of predatory behavior, and direct evidence of scavenging behavior.

As Dr. Hone puts it:

Tyrannosaurs were indeed scavengers, and predators.

And that"s the current scientific consensus. They were predators and scavengers.

Further, there"s no direct evidence of pure scavenging behavior in other large tyrannosaurs like Daspletosaurus, Tarbosaurus, Lythronax, or Albertosaurus.

They all show evidence of direct predatory behavior, and scavenging behavior.

The reason I"m drilling this home, is that so many people keep perpetuating the myth that T. rex, was a pure scavenger, despite the complete lack of evidence for obligate scavenging behavior, and need to update their information to include the numerous fossils that demonstrate predatory behavior.

It also goes against common sense, as the only obligate scavengers that we know of are vultures. Previously, animals like hyenas were once thought to be obligate scavengers, until zoologists found evidence that they hunted too.

So, guys, stop perpetuating that myth. T. rex, was a capable hunter in its own right.

Another fun fact, we have found fossilized Tyrannosaurus rex dung, called coprolite (I believe the technical term is a shit brick), and you can analyze what the animal ate.

It contains a lot of juveniles of what it preyed upon.

image

Here’s the source for the study, which is from the American Museum of Natural History, a reputable source that I can trust to summarize the study they reference accurately.

What Fossilized Scat Shows About T. rex Bite | AMNH

What can we glean from their scat, besides like everybody else, they also had to take the Browns to the Super Bowl?

Well, they’re specifically targeting the young, defenseless, the old, and the weak.

This isn’t out of the ordinary for any other predator in the entire 4.5 billion year history of this planet. Predators don’t go after the strong, healthy adults, because any injury that a predator sustains could be potentially fatal.

In fact, many people seem to look at the carnivorous dinosaurs and suggest they are the most dangerous dinosaurs that lived, but completely ignore how dangerous a fully grown, healthy Triceratops is.

I mean, look at them!

image

This is a creature the size of an elephant, with nasty horns on its face, a nasty attitude, and as the fossil evidence suggests, can fight off other Triceratops and even things like the famous brute that is Tyrannosaurus rex.

If I was a T. rex, no freaking way would I even think of targeting a healthy adult. I’d probably go after something much easier, like a juvenile.

The previous paper by Dr. Hone and Dr. Watabi suggests, as Dr. Hone puts it, is that T. rex, and indeed the other large tyrannosaurids, are actually selective and careful feeders, in that they can choose how they bite and where they bite.

So basically, T. rex was a large, powerful animal that had the strongest bite force of any terrestrial carnivore that has ever lived, and was essentially so large and powerful, that it was basically the apex predator of its ecosystem.

It could hunt very well, considering its got the power, the speed, the eyes, and the smell to do it, and it could also bully other of its kin away from kills and feast.

In fact, the fact I even said it could bully other animals around also shows a fun fact about T. rex and large tyrannosaurids, which we will discuss in the section about social behavior.

TYRANNOSAURUS REX ONTONGENY:

T. rex ontogeny is actually something we can infer and look at, and it has some interesting implications about the ecology of the juveniles compared to the adults.

Because T. rex, even amongst its closely related relatives, is actually a bit of an outlier in all things really.

Also, considering we have several specimens ranging from hatchlings to juveniles, to sub-adults, and full grown adults, we can actually plot the growth stages of T. rex.

image

This graph by Franoys looks at different specimens from hatchlings, like the adorably named Chomper, to full grown adults like Sue and Scotty.

As the provided graph shows, during the first few years of a new T. rex’s life, it kinda slowly grows.

Until about 10–12 years old then the animal absolutely balloons in length, mass, and height.

While tyrannosaurs, and really, dinosaurs in general grew up pretty fast, T. rex is such an outlier that when comparing it to its other kin like Daspletosaurus, Gorgosaurus, and Albertosaurus, that T. rex’s growth curve is far more pronounced.

image

I mean, look at that. All of the other tyrannosaurs get to about full grown at 15 years old, whereas Tyrannosaurus has massively ballooned to being much larger than them, and it keeps growing until around 20–25 years old it reaches adulthood.

Interestingly, this is about the maximum growth spurt that we humans have, but with T. rex, that growth spurt is being sustained for multiple years!

One can only imagine the growing pains of a Tyrannosaurus…

Not only this, but T. rex dramatically changes shape as they grow too.

This isn’t out of the ordinary really. We colloquially think of puppies and kittens as having these kinda huge heads, eyes, and paws, and they sort of grow into them.

But, even more fascinating, is that with Tyrannosaurus, the proportions are changing as well!

Here’s a comparison of T. rex skulls.

image

On the bottom we have Chomper, just being a cute lil fella.

Above him, we have Jane, a juvenile. We see the teeth grew larger, and the snout longer, and such.

And then, we have at least a sub-adult or an adult, and just look at how much it’s ballooned in size!

Basically, T. rex went through such a dramatic growth spurt, that it went from an animal that could barely wrap its mouth around your arm, to being able to swallow a full grown person whole.

And yes, with the full grown adults like Sue, Stan, Scotty, and Queenie, you can fit inside of a T. rex mouth, and it could have swallowed you in one bite.

image

And I’m not done yet!

If we look at the specimen Jane:

image

We can see that she’s more lithe in build, with great long legs.

Jane’s roughly a juvenile around half grown up, and yet the head is absolutely tiny compared to a full grown adult like Scotty:

image

Since the head’s built differently compared to an adult, the neck is skinnier, the body’s overall more gracile in appearance, this actually suggests that the juveniles are engaging with different prey than the adults.

The implication is that the juvenile T. rexes are fundamentally changing their ecology as they grow!

The adults are using their mass, their power, to wrestle down and kill larger animals, while the juveniles were smaller, faster, and probably chasing down fast running prey.

So in actuality, Tyrannosaurus ontogeny is quite unique, and why I labeled them as an outlier, especially compared to their closely related kin.

So in actuality, juvenile T. rexes weren’t just merely smaller versions of their parents.

In actuality, their build was more gracile, longer legs, and much smaller heads.

When thinking of a juvenile T. rex, don’t think of this:

image

Think more like this:

image

Of course, everyone knows about the adults, but T. rex ontogeny shows us that the Lost World baby T. rex is just inaccurate.

With the talk of hatchlings, juveniles, and ontogeny, and the juveniles fundamentally changing their predatory ecology as they grow and mature, this leads to a perfect segue into our final piece of this answer.

TYRANNOSAUR SOCIAL BEHAVIOR:

The evidence for pack hunting behavior in large tyrannosaurids is slim, as all we really have to go on are fossilized track ways of a group of tyrannosaurs moving in the same direction.

But again, inferring pack behavior from this is quite a leap in logic, as there’s other, plausible explanations for this piece of evidence that are equally as valid, like say, gathering to mate.

Of all the evidence, evidence of cannibalism and intraspecific competition are rampant in Tyrannosaurus rex, specifically.

This points to a highly territorial, solitary hunter.

This study actually discusses intraspecific competition in T. rex.

Intra-guild competition and its implications for one of the biggest terrestrial predators, Tyrannosaurus rex

In fact, several specimens of Tyrannosaurus rex show evidence of healed bite wounds from other T. rexes specifically targeting the head, neck, and face, meaning they fought each other by biting their heads, necks, and faces.

Mark Witton discusses in his blog the wounds of a famous T. rex specimen, Stan:

image

Stan"s skeleton is particularly damaged around the posterior head and neck region, with a probable tooth wound penetrating it"s braincase, a smashed postorbital bar (a dorsal projection of tyrannosaur skulls which anchored neck muscles) and broken neck vertebrae.

What neck-biting Tyrannosaurus sex tells us about speculation in palaeoart

And yes, you read that right, this head and neck biting behavior isn’t just an explanation for competition for food, but for mates, and was apparently a behavior they engaged in during sex!

Man, the life of a Tyrannosaurus is a tough one.

Your parents may or may not acknowledge your existence, and if they do, there’s a 50–50 chance of them looking at you as a snack, and if you survive to be a juvenile, your brothers and sisters are competing with you for food, and even if you survive to be an full grown adult, you have to deal with other of your kin battling you for food, and once you do reproduce, your partner is into a vicious biting kink.

PALEO-ART:

Now to bring this all together in awesome paleo-art that actually depicts the animal accurately.

image image

I actually rather like this one of a T. rex just resting. Hey! He’s had a hard day! Cut him some slack!

image image

SUMMARY:

In summary, the depiction of Tyrannosaurus rex in the Jurassic Park film franchise is inaccurate, and rather outdated.

The animal looks horribly shrink-wrapped compared to what science now knows what the creature should have looked like.

Details about its anatomy don’t suggest that the films’ version is, indeed, Tyrannosaurus as we know it, but just looking at the animal in the film suggests that it has much more in common with genus Tarbosaurus.

Hope you guys enjoyed this answer! :D

For an amazing summary by an expert, I strongly advise anyone to watch this lecture by Dr. David Hone. When I first watched it, it was an hour that just flew by.

EDIT: Updated to include an actual ratio of T. rex’s arms compared to its body, and how a very closely related relative, Tarbosaurus bataar, had an even smaller ratio.

Regarding Tyrannosaurus and Tarbosaurus, I like to think of them as this:





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