Over on AAB I have been debating the relative sizes of the giant theropods Tyrannosaurus and Giganotosaurus with sauropod expert Mike Taylor. Those regular readers of this blog will know I have a longstanding interest in dinosaur body sizes and mass estimates and they are a question that comes up again and again when then the public or media get to grill palaeontologists, if only as framed as “which was the biggest?”.
These are however a very interesting pair of taxa and illustrate a few concepts quite well (namely different concepts of being the ‘biggest’) and are often foremost in people’s minds when they think of giant dinosaurian predators. Tyrannosaurus is famous for its size and is probably one of the most recognisable dinosaurs going, and there is little doubt it was huge – around 12 m in length and something like 8t in mass. For a very long time it was regarded as the largest terrestrial predator and the absence of any detailed information about Spinosaurus (rapidly followed by the absence of any material following World War II) meant that until recently, Tyrannosaurus was pretty much unchallenged. Then a flurry of discoveries in South America threatened the crown of the king severely, most notably through Giganotosaurus, a real giant and almost certainly taking the crown for the longest theropod known at a round 14 m, though Tyrannosaurus was quite probably heavier.
This gives me the opportunity to wheel out this image that I produced for a grant application I made of giant predators that gives you an idea of just how big some of these got. At the front you have a Siberian tiger (white – the largest living terrestrial predator) and Andrewsarchus (grey – the largest known mammalian predator, though its status as a carnivore has been questioned) and then across the back Spinosaurus (white – actually drawn too large, it has recently been scaled back a bit from this and the biggest carnosaur), Giganotosaurus (black – the biggest allosauroid), Tyrannosaurus (grey – the biggest tyrannosaur) and Carnotaurus (white – the biggest known abelisaur). As you can see Tyrannosaurus is massive by any measure, but what interests me is the actual build of the animals and most notably the respective skulls of our featured animals.
This post was inspired by the fact that I ended up discussing (i.e. arguing) about them with Mike the day after I spotted this image online via my colleague Canadian palaeontologist and Tyrannosaurus specialist Eric Snively who kindly passed it on. It is made from CT scans of sculpture reconstructions, of Sue (the famously complete and very large Tyrannosaurus, by Brian Cooley) and the type of Giganotosaurus (by Maria Gravino). It’s taking a team from five countries to turn these into finite element models for bite force comparison research I am I very grateful for being allowed to use it.
- Tyrannosaurus vs Giganotosaurus
The scale may not be exactly right, but it is good enough and it really demonstrates the point I want to make. Tyrannosaurs might not be the longest, or even the heaviest theropod, and certainly it *is* the most over exposed and overstudied, BUT it is also has an absolutely huge skull for its size. Not only is the skull pretty much the same in overall dimensions as that coming from an animal supposedly much larger than itself, but that cranium is far far more massively built. The skull is incredibly robust and well built in comparion to that of Giganotosaurus. It really gives you a feel of just how different and specialised Tyrannosaurs seems to be, since Giganotosaurus really does have a pretty ‘typical’ theropod skull, if a very big one.
Just reading all the Ask a Biologist posts.
I love the way you guys can argue and yet keep it nice. A few of the palaeo sorts I know can’t keep it civil for long (especially when arguing about T-Rex ;p ). Its nice to see friendly debates over this stuff.
Also as a frequent user of AAB thanks to you guys for running it!
Thanks for the comments. We do try to specifically keep it as friendly as possible and it helps that AAB is a relatively small core of people and thus most of us know each other (if only through working on the site). Still, it does get really pretty heated at times and some threads (notably the zebra one I highlighted recently) can runa dn run. I actually think that’s an incredibly important part of the site as it shows people that we are not just dogamtic and on soem issues at least there are disagreements, contradictory evidence and even, yes, mistakes. I have genuinely learned alot from the site myself which is a pleasent surprise.
So…WHY is T rex so heavily built in the skull compared to the big G and other theropods? It would imply to me that it needed the extra bite force…but why? Ceratopsian issues?
It would seem to be a function of feeding / biting. Work suggests that allosaurs (and Giganotosaurus is in many ways a giant allosaur) had a relatively weak bite and relied on the impact of the momentum of the animal to deliver power to a bite (i.e. hitting the prey with the mouth open) wheras the derived tyrannosaurs quite simply had power delived from the actual muscles of the head to make the bite strong. This my be the end of it – it’s merely a difference in style than any special requirement of the tyrannosaurs (cheetahs, lions and hyenas all hunt the same prey types just in different ways). I rather susepct that there are other factors at play as well, but since the grant got rejected, I can’t tell you
What a coincidence! I’m just posting the last post on my arctometatarsalian week, and compared briefly the tyrannosaurid pes with the allosauroid one…
Don’t forget Deltadromeus, (probably) the biggest known ceratosaur! The holotype is a subadult, but based on the referred specimen cited by Sereno et al (1996), its adult femur was 1.2 m long…
*And* as it happens I have just been taking photos of a nice tyrannosaurian arctometatarsal that I want to post on! As for Deltadromeus, i left it out of the image (which is 2 or 3 years old now) becuase at the time it was still listed as a basal tetanuran, and I’m still not sure how certain people are that it is a ceratosaur.
What arguments are being made for Andrewsarchus not being a carnivore? Are people suggesting that it was vegetarian? Or are they just saying it was an obligate scavenger?
I really like that size comparison image, Dave. What’s this I hear about Spinosaurus being scaled back? Is this more recent than the Dal Sasso paper regarding the partial snout fragment? Also, you’ve gotta get Gigantoraptor in there, now that it’s the largest known maniraptor!
Dave, I just read somewhere (and sorry I can’t remember and obviously could not afford to bring my mammalian papers to Beijing!) that it was possibly an omnivore, based I belive on molar shape. I really can’t offer much more than that, but it was in a paper I was able to hunt down while in Germany so it’s probably online, you can take a gander at Google Scholar.
As for Spinosaurus, I think it was the Thierren and Hhenderson paper that suggested the Dal Sasso estimate of 17m was perhaps a touch too big. Sorry about the half answers but I am absolutely swamped right now – two grant applications to get out this week and a couple of appers are well overdue…
You say that the Siberian tiger is the largest living terrestrial predator, I thought that title was taken by the polar and/or Kodiak bear?
What is the citation for Thierren and Henderson’s paper? Thanks…
Masloski – I didn’t include them becuase they are not terrestrail hunters – the kodiak is typcially considered an omnivore and the polar bear gets most of it’s food from the seas which includes hunting in open waters. The focus of the grant which thay image comes from was terrestrial macropredators and large body sizes and thus neither of those two bears really counts.
Steven – the reference is available here: http://www.bioone.org/perlserv/?request=get-abstract&doi=10.1671%2F0272-4634(2007)27108%3AMTIBTY2.0.CO%3B2
Perhaps the term terrestrial carnivore would have been better over the term terrestrial predator. Kodiak bears are terrestrial predators (they prey on other animals) but not terrestrial carnivores (since they’re actually omnivores). Just a thought.
G-carolini is king! FOREVER! HE ALWAYS WIN TYRANNOSAURUS! HA-HA-HA! GIGANOTOSAURUS THE KING OF DINOSAURS!
giganotosaurus is the best,samer as carcharodontosaurus, these have the tittle of the greatest carnivoures dinosaurus
sorry 4 my bad english
You know, I’ve been wondering…if Giganotosaurus ate titanosaurs and rebbachisaurs, then why shouldn’t it have stronger jaws than T-rex; it’s almost like T-rex wants to make a quick kill when it’s dealing with prey smaller than itself, or else, that is comparable to it, whereas giganoto was taking on creatures that were obviously much bigger (although it would obviously have preferred juveniles sometimes). Also, don’t forget Alamosaurus…
I’m furthermore curious about what shuangmiaosaurus the Asian iguanodont looked like? Was it like an Iguanodon, or else like a Camptosaurus or Tenontosaurus?
Well that rather assumes that they were hunting large adult animals as opposed to juveniles (as i have rather strongly suggested on these pages recently) which eleminates much of the size discrepancy.It also depends on what those jaws are doing. Lion shave less robust jaws than hyenas but can kill and eat elephants which hyena do not. Size and power of jaws do not equal size of prey.
As for the igunaodontids, sorry but really not my area. I can tell you though that they are very conservative – that is one igunaodontid looks very much like another and differences can be pretty limited.
I’d further like to know when Zhuchengosaurus lived (during what stage)
Same basic strategy as hyenas when hunting–though their jaw strength is incredible (so far as I know it’s mainly for bone utilization), when attacking large prey (like water buffalo/wildebeest) they don’t hold onto them the way lions do, but rather bite the target enough to bleed it to death (one video in particular shows a hyena grabbing hold of a wildebeest’s intestine and running away with it).
When something’s that much larger than you, it’s much easier to just let it bleed until it expires instead of latching on and shaking.
Hell, with hyenas expiration isn’t even really required. They’ll frequently eat their prey alive if they know they can get away with it.
I’m not an expert, but basing myself on logic, if you are larger then your intended prey you’d rather hit, crush his spinal bone and kill it with a single powerfull bite.
If you are barley faster then your prey you need to close from an unexpected location like a tree spot, and hit as fast as you can, because your body mass can tire you down fast when you are getting after something that can keep distance from you in a run.
So, ambush, evaluate distance (binocular wiev) dash at the right time (big brain), kill with a powerfull bite.
In the southern emisphere, when chasing a large slow terapod you need help. You need to tire him down, bleding it down and take your time for the kill, because he is much stronger then you.
Once the prey is dead there will be food enought for the whole pack. You probably couldn’t kill him with a single powerfull bite because his bones would be too strong even for a tarbosaurus bite, so you need to bite and slice off letting the bleed do the hard work. A pack of Giganotosaurs (or Carcharondontosaurs) hitting a lone Titanosaur would probably perform like a pack of Raptor hitting a lone Mayasaur in north america.
Furtermore, powerfull maws like those of a T-Rex could be dangerous for you, assuming you can’t overpower the beast you are fighting: immagine a bulldog with the jaws colosed on a large beast like a bull being shaked around, but the Buldog just weight 30kg: now thry to immagine a T-Rex in the same situation… I’d bet his neck would snap under the sheer weight of his body.
So, in conclusion, Alosauroids were the best conceivable shape to kill large terapods, while the Tiranosaurids excelled in killing moderately large bipedal Anatosaurs or whatever else they hunted
I think that any large prey is potentially dangerous to any predator, whether alone or in groups. If you read my work on theropod hunting behaviour you will see that almost no living animals (of any kinds) preferentially hunt adult prey – the almost all prefer juveniles for a variety of reasons, but a prime one being a reduced risk of injury. In the wild, any serious injury (and even some minor ones) can be fatal and as a predator you risk that every time you go hunting, so you need to minimise that risk, and avoiding adults (whether they have armour, or spikes, or horns or even nothing but their size) is therefore a very good idea.
I also think you are overestimating the abilites of predators to kill animals quickly. If you look at the bite record we have for T-rex, it’s powerful yes, but able to kill in one bite? Almost certainly not, unless the prey was much smaller than itself. Cats can kill mice in one go, but they struggle with rabbits for example, and here we are mostly dealing with animals multiple times bigger than the proposed predator.
There is (sadly) no good evidence (or at least none that is especially convincing) for pack hunting in any theropods (as yet) but there is more to come. Certianly our knowledge of allosaurs is much lower than that of tyrannosaurs, but do remember that a) many titanosaurs had armour and b) those sauropods that did not were often very big indeed and both types probably lived in herds. In either case, they would be a challenge for even packs of allosauroids and thus not a tempting target when hundreds of unwary and less protected juveniles were available.
You are right about the danger of killing large anomala, and I bet as well that weak an juvenile target erre always preferred.
My assumption was about the fact that a tyrannosaur hunting, say, a mayasaur, would probably go for the neck, because it could easilly decapitate his prey with a single byte.
Obviously this was bot necessary because a single byte of thecsize and the strenght of a t-rex wasvoften potentially lethal.
The reason of this is that t-rex prey were no big enough to survive, and te size of their bones,enough robot be crushed.
This is not the scenary which a typical allosaurid would face, and I dee a reason in the fact the Carcharodontosaurs survived wherevte prey were large, and exticted elsewhere.
Allosaurs dominated the Jurassic but exticted in the cretacean in North America, replaced by Daspletosaurs and later T-rex.
In Africa and in the South America Were their prey were more similar to’ the Jurassic ones.
Evolution talea ages, but mostly makes sense.
For this reason raptors were bigger in the south.
All this assuming the T-rex was indeed a predator target then an occasionali killer.
But if you accept that these predators would preferentially target juveniles then the rest becomes largely irrelevant since in either case the predator (allosaur or tyrannosaur) would be much bigger than their prospective prey. So all the variation comes down to (or could anyway) different ways of tacking the prey rather than the different prey itself. We have hyena, hunting dogs, cheetah, lions and leopards all co-exisiting and hunting similar or the same species in Africa. Just being different can reflect different strategies. Asiatic lions are very similar to their African cousins yet do not (and cannot) hunt wildebeest and zebra in open plains. In short prey can vary, but that need not vary the hunting mechanism and associated morphology.
(sorry for bad english: i’m on a cellular phone and spelling corrector messed all up >__>)
No problem, don’t worry!
To further elaborate, we could assume the giganotosaur albeit huge, fighting as a fencer, with optimal all around situation awarness to ward off from side attack (whip tails, other animals, ecc), and the Tyrannosaur fighting as a bruiser, to fast overpower the prey, dashing out at the right moment, with optimal stereoscopical vision. The large olfactive lobes Aldo male dense of you act as a scavengers too.)we could immagine the T-Rex as a Tiger and the allosaurs as wolved.
Another reason for the dofference in the jaw aspect between the carcharodontosaurids and the tyrannosaurids may be the way they feeded.
Let’sagine the T-rex acting like a sort of big hyena, which consume his prey entirely bones included to’ sustain his large body with relatively small preys, and countin on his size and streght to’ jeep other scavengers at bay while it ate. As for the allosaurids, assuming they hunted in packs (which is likely, given the size and strength of their preys, they could have hunted, killer, ate, without need to consume the whole prey (which was oversized) and this did not required such powerfull jaws to crush the bones (which were oversized too).
I think you are over extrapolating here. We really don’t know that much about how these animals hunted or fed, or how prey species could defend themselves. To my knowledge there is no direct evidence of any carcharodontosaurids feeding on large sauropods (I expect there are some bite marks somewhere that are unreportrd, but I’m not aware of any) let alone healed bite traces that indicate active predation attempts. As such, whole I am sure these were occasionally attacked, to try and work out entire evolutionary patterns of hunting behaviour based on the assumption that species X hunted species Y in manner Z is rather pointless at the moment since there is just no good evidence to support any part of it, and as I note above there is a lot of variation and overlap seen in which animals hunt which others and how.
You are right and I got a little caried away here.
There is no solid proof of the Carcharondontosaurs feeding on large sauropods, and even what little we know of their cousins, the Jurassic Allosaurs, is based on the assumption they actually preyed on adult apatosaurs instead of just occasionally feeding on carrions. Still we have proof of Allosaurs teeth on adult Apatosaur bones, as well as Tyrannosaur teeth on Triceratops… But if we relate the behaviour of Giganotosaurs to that of ancient Allosaurs we MUST take in account how many Alosaurs skeleton sohow sign ofdamages and hard fighting, menaning this was a very agressive specie
May we assume the T-Rex actively feeded on adult triceratops because of teeth sign on Triceratops skeletons?
I doubt that except in desperate cases because of the danger they would have faced.
About the Tyrannosaurs we know little more then this because we know they “could” kill but there are speculations about them being little more then scavenger, bullying other predators with shear size and force, as the large olfactive lobe seems to suggest (find carrions at very long range).
Beware, Im not implyng that Allosaurs were killers ad tyrannosaurs carrion eater. We simply don’t know.
But keeping on speculating, why then the Allosaurs desappeared form the north Amercian continent with the extinction of the large Sauropods, but we still find them prosperating in Africa and South America, where these sauropod were still rather common?
We know they faced active competition from other carnosaurs, like the ceratopsian, and we know the size of these increased in the souther emisphere as much as the Allosaurid did.
But I guess
So we found a clear mark disticntion between the Along the cretacian Tyrannosaurids and the Carcharodontosaurids: the first ones propsered where the climate was less humid and where the Ceratopsids and Adrosaurs prospered, which means north asia, and north america. The seconds propsered where the climate more resembled what it was like in the jurassic era, with large sauropods and a relatively humid climate.
Interestingly, we found the the only cousin of the Allosaurs in NA did not fared so well (given the number of fossiles we found), while in SA we did not found other Tyrannosaurids.
We don’t know if this is related to “phisiology of social behaviour of the two different kinds.
We may speculate the allosaurs were better suited for pack hunt to large animals where the tyrannosaurids were better at ambushing and killing moderatley sized beast alone, or with small family groups? We dont know.
Interestingly the only part of the globe where the Allosaurs were not found side to side to larger plant eaters was in Antartides where may be it was isolated and faced much less cocnocrrence by other predators
I’m sorry but once more I think you are over extrapolating based on a lack of evidence and
“but if we relate the behaviour of Giganotosaurs to that of ancient Allosaurs we MUST take in account how many Alosaurs skeleton show sign of damages and hard fighting, menaning this was a very agressive specie”
- But so do many extant animals too – modern carnivores often break their teeth and are left with minor injuries inflicted by prey and accidents during hunting. As predators get older they become much more susceptible to these kinds of injuries as well. You’d need to show that Allosaurus was especially vulnerable and I don’t see any evidence of this. Certainly there are lots of other theropods showing injuries of similar kinds to those in allosaurus.
“May we assume the T-Rex actively fed on adult triceratops because of teeth sign on Triceratops skeletons?”
- Fed on the bodies, yes. Killed, no. There is no good evidence for them actively killing adult Triceratops – an important distinction.
“why then the Allosaurs desappeared form the north Amercian continent with the extinction of the large Sauropods, but we still find them prosperating in Africa and South America, where these sauropod were still rather common?”
- True, but then the tyrannosaurs were also appearing at this time. Was this change caused by changing flora, changing herbivore populations or changing predator populations. And the sauropods did fine in Asia and the southern part of North America where the allosaurs still died out, so this is hardly a very unambiguous pattern.
“while in SA we did not found other Tyrannosaurids”
- But this could be becuase they never made it that far south rather than this was an unsuitable habitat for them.
“Interestingly the only part of the globe where the Allosaurs were not found side to side to larger plant eaters was in Antartides where may be it was isolated and faced much less cocnocrrence by other predators”
- I assume you mean Antarctica, and here we have so few fossils I think it’s meaningless to make any serious statements about the faunal composition as we really have no idea what it was like there.
You are of course welcome to speculate about how these animals may have lived and acted, but I really think you are overlooking big contradictions to some of your basic assumptions and extrapolating across places where there is very little data to support any ideas.
As you say I “AM” extrapolating since there is very little else to do about very rare animals like the Carcharodonosaurids.
How many skeletons in good SHAPE we have to try an extensive survey of how they lived?
We chose to assume all these predators, like the t-Rex were active hunters rather then carrion eaters, because the mass of their supposed preys, the ammount of food they ate, the age of the adults, suggests just sitting aroud waiting for them to die of age or illness would have been impractical.
Then because of the similiarities between Giganotosaurs and Allosaurs, both in Shape and habitat we have to speculare they filled the same niche.
I’m no expert, i admit, just fascinated by these animals, but i try to speculate on facts of I can: for example, we know the allosaurs in North America was prone to absorb a lot of punishment along their life, usually more them other carnivores of the era, like ribs and leg fractures, much more in facts then the tirannosaurids (another well known and well studied predator) several millions of years later which, to me, means (speculating again) that their environement was more dangerous, possibly because of stronger preys or killing patterns.
I don’t know if this is entirely applyable ro their late cousins, the Carcharontosaurs, larger and heavier, but is a fact that the plans of south America in the cretacean had a lot in common with the Jurassic North America in climate and fauna.
If we assume allosaurs were sauropods preyer, it’s relatively safe to assume the same for their late, southern cousins in the cretacean.
And I’ll go for another pure speculation: what if the hunting abit of the allosaurids tied them strictly to the large sauropods, so that they prospered wherever the large herbivores lived?
I’m trying to parallel the lions in the savana, with the Tiger in the forest: large packs of predators for large and abundant preys (which are often larger then the predators themselves, like zebras and buffalos), vs solitary hunters trying to ambush smaller preys alone overpowering them with size and strenght
“the age of the adults, suggests just sitting aroud waiting for them to die of age or illness would have been impractical.”
- I’m not suggesting this – I’m suggesting they ate the juveniles and largely ignored the adults.
“i try to speculate on facts of I can:”
- That’s fine, but as I note, the facts are largely few and far between, so you can fill in almost any story or concept between the few facts we have and it will fit. As a result, it doesn’t get you very far. You can equally say allosaurs are pack hunters, or lived alone, or predates sauropods mostly or stregosaurs mostly and there is nothing to show either is right or wrong, hence I think the speculation is fun, but meaningless.
“, usually more them other carnivores of the era, like ribs and leg fractures, much more in facts then the tirannosaurids”.
- Where have you got this from? I’m genuinely interested – is there a paper on this? I’ve never seen any work suggesting this as a pattern.
“If we assume allosaurs were sauropods preyer”.
- That is a huge assumption and we do have evidence of allosaurs at least feeding on stegosaurs, and probably killing them too.
“what if the hunting abit of the allosaurids tied them strictly to the large sauropods, so that they prospered wherever the large herbivores lived?”.
- But as I noted, this can’t be the only factors since the allosaurs and their kin do not do well in Asia in the Late Cretaceous of Asia where there are still sauropods and in southern North America too.
“lions in the savana, with the Tiger in the forest”.
Well yes, but there are also lions in the forests in India and in Africa in places. And then there are leopard, hunting dogs, hyena, dhole, cheetah and more. You can’t ignore the other predators either in one system (modern times) or the other (dinosaurs). And here the parallel shows the opposite I think – tow very closely related sister species that have very different hunting patterns, showing just how much variation you can have even within Panthera, when you are trying to compare different families but maintaining consistnecy within those clades.
Not that I would not expect tyrannopsaurs to be generally similar and allosaurs to be generally simil\r, but this example does not serve your ideas well.
I’ll try to find the charts about Allosaurs phisical damages.
but I’ll not able to do that untill monday I think
Sorry for the delay.
I checked the charts but I can’t find nothing conclusive about the damages and fractures on allosaur skeletons.
The only reference I found (and probably what trigged my memory) is about an old history channel program showing a recostruciton of what may have happened in a bollodbath near a water poll (three allosaurs and a ceratosaur probably killed in a fight with a two styracosaur and a camerasaur get bogged down in themud. Here a paleontologist tells that many allosaur skeletons show sign of stress and damage.
Not the best of the sources but still someting.
I cant confirm nor negate the autenticity of what the Palontologyst says.
Well yes that’s hardly convincing evidence that allosaurs were at more risk of injusry than other theropods. Even if the situation you describe didi happen it could still be considered and exceptional event rather than a normal predatory situation and thus again not exactyl convincing.