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Allosaurus fragilis v Yutyrannus huali
Topic Started: Oct 14 2013, 07:14 PM (5,113 Views)
Taipan
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Allosaurus fragilis
Allosaurus (play /ˌælɵˈsɔrəs/) is a genus of large theropod dinosaur that lived 155 to 150 million years ago during the late Jurassic period (Kimmeridgian to early Tithonian). Allosaurus was a large bipedal predator. Its skull was large and equipped with dozens of large, sharp teeth. It averaged 8.5 meters (28 ft) in length, though fragmentary remains suggest it could have reached over 12 meters (39 ft). Relative to the large and powerful hindlimbs, its three-fingered forelimbs were small, and the body was balanced by a long, heavy tail. As the most abundant large predator in the Morrison Formation, Allosaurus was at the top of the food chain, probably preying on contemporaneous large herbivorous dinosaurs and perhaps even other predators (e.g. Ceratosaurus). Potential prey included ornithopods, stegosaurids, and sauropods. Allosaurus was a typical large theropod, having a massive skull on a short neck, a long tail and reduced forelimbs. Allosaurus fragilis, the best-known species, had an average length of 8.5 meters (28 ft), with the largest definitive Allosaurus specimen (AMNH 680) estimated at 9.7 meters long (32 ft), and an estimated weight of 2.3 metric tons (2.5 short tons). In his 1976 monograph on Allosaurus, James Madsen mentioned a range of bone sizes which he interpreted to show a maximum length of 12 to 13 meters (40 to 43 ft). As with dinosaurs in general, weight estimates are debatable, and since 1980 have ranged between 1500 kilograms (3300 lb), 1000 to 4000 kilograms (2200 to 8800 lb), and 1010 kilograms (2230 lb) for modal adult weight (not maximum). John Foster, a specialist on the Morrison Formation, suggests that 1000 kg (2200 lb) is reasonable for large adults of A. fragilis, but that 700 kg (1500 lb) is a closer estimate for individuals represented by the average-sized thigh bones he has measured. Using the subadult specimen nicknamed "Big Al", researchers using computer modelling arrived at a best estimate of 1,500 kilograms (3,300 lb) for the individual, but by varying parameters they found a range from approximately 1,400 kilograms (3,100 lb) to approximately 2,000 kilograms (4,400 lb).

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Yutyrannus huali
Yutyrannus (meaning "feathered tyrant") is a genus of tyrannosauroid theropod dinosaurs from the Early Cretaceous of China. Three specimens of Yutyrannus huali found in the fossil beds of Liaoning Province are currently the largest known dinosaur fossils that preserve direct evidence of feathers. Yutyrannus contains a single type species, Yutyrannus huali, named and described in 2012 by Xu Xing et al. The generic name is derived from Mandarin Chinese yu (羽, "feather") and Latinised Greek tyrannos (τύραννος, "tyrant"), a reference to the classification as a feathered member of the Tyrannosauroidea. The specific name consists of the Mandarin huáli (华丽, "beautiful"), in reference to the beauty of the plumage. Yutyrannus were gigantic bipedal predators. The holotype and oldest-known specimen has a length of 9 metres (30 ft) and an estimated weight of about 1,414 kg (3,120 lb). Its skull has an estimated length of 905 millimetres (35.6 in). The skulls of the paratypes are 80 centimetres (31 in) and 63 centimetres (25 in) long and their weights have been estimated at 596 kilograms (1,310 lb) and 493 kilograms (1,090 lb) respectively. The describers established some diagnostic traits of Yutyrannus, in which it differs from its direct relatives. The snout features a high midline crest, formed by the nasals and the premaxillae and which is covered by large pneumatic recesses. The postorbital has a small secondary process, jutting into the upper hind corner of the eye socket. The outer side of the main body of the postorbital is hollowed out. In the lower jaw, the external mandibular fenestra, the main opening in the outer side, is mainly located in the surangular.

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thesporerex
Oct 14 2013, 02:59 AM
Yutyrannus vs allosaurus
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theropod
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I'm not aware of any comparison of the dentition of both, or even any data on that of Yutyrannus. How did you conclude one ahd the superior dentition?

The neck is a more likely target than the skull for interspecific confrontations. As you point out, theropods are known to have survived plenty of facial trauma.

It is relatively rare for animals to target the skull for killing large prey, and would be even rarer in animals like these, with large skulls and small brains hidden deep inside them.
On the other hand, their morphology allows these animals (that is, the majority of theropod, with the exclusion of tyrannosaurines and Abelisaurids, both taxa apparently specialized for prolonged prey contact with the jaws) to claw into and reposition relative to the prey or opponent effectively.
Added to that, breaking free from the relatively weaker grip of a shlasher (given it even attempts to restrain something with the jaws) would only increase the already great damage that would have been caused. You could certainly pull your arm from the jaws of a komodo dragon more easily than from the jaws of a similar-sized crocodile, but I doubt you'd really want to do that.
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Bandog
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Reading about allosaurus' dentition suggests that it had a superior bite, enhanced by the gape and sturdy skull.
As for targeting the skull, I don't see why they'd go past the main killing apparatus to get the neck, especially if the opponent can kill with a bite to the skull (tyrannosaurus likely could to animals with less sturdy skulls). For example, if a theropod tries to get past a tyrannosaurus' head to bite its neck, the tyrannosaurus can bite the skull before it reaches the neck. This answers the last paragraph as well, I don't see a serrated bite causing life threatening injuries to the snout, maybe closer to the back of the head it could.
That last analogy isn't really any good. My arm isn't the neck of a multi tonne predator though in that instance, id have more chance of killing whichever animal I could break free from I guess. While the Komodo might leave my arm inoperable, the croc could potentially amputate the arm.
There's no real need to discuss this further though, it's been done to death and I'm out of my depth in these topics.
Also, sorry to use tyrannosaurus so much but his skull is the best example of the point I'm trying to make.
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theropod
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Yes, the main and most important part is that is could, eg. in the region of the jaw musculature and blood vessels and the cranial nerves innervating them. Even a tyrannosaurine would need to bite the back of the skull to actually cause fatal damage, even tough it could cause horrific injuries on the snout. But catching and placing a proper bite on the skull before it even got to the neck would not be an easy task to perform, with limited gape and striking range.

Using the jaws to control an opponent can more easily be employed with a robust mandible and strong bite force, at least in the way you have in mind. However this has other disadvantages, such as slower striking and longer prey contact being required to be damaging.

Whether your arm is inoperable or amputated (btw I doubt a komodo-dragon-sized croc could do that, but I might be wrong) doesn't make a difference, However you'd probably have better chances to survive as long as your arm was in the jaws of the crocodile than after you pulled it out of the jaws of a komodo dragon, because the latter would cause extreme bleeding...

I'm not so sure about this one. While what you write about Allosaurus is definitely true, we have no clue about the condition in Yutyrannus, so automatically assuming inferiority is a bit premature. It is possible the tyrannosauroid also had big gape and sturdy skull, these are features not studied on it, just like the cutting potency of its dentition.
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Bandog
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Allosaurus seems uniquely adapted to support its biting mechanism. The neck was seemingly very flexible and well suited to pulling upward compared to lateral shaking, suggesting it is using serrations to cut meat from prey. Against a theropod without truly bone crushing force, similar shearing capabilities or another method that I'm unaware of, allosaurus seems to have the advantage in killing potential.

Edit: happy birthday!
Edited by Bandog, Oct 31 2013, 01:05 AM.
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Vobby
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Fossils tell us that theropods targeted the head in intraspecific fights, and the same is true for extant theropods, although the majority of them use mostly their feet to fight. I don't see the reason to involve arms so much: even if this two theropods could really use them to fight a similar sized opponent, it's clear that their main grasping and wrestling organs are the head and neck, which sport much more muscles than their shoulders and arms.
If I remember correctly, the only fossil we have with a claw wound in it is from Deinychus, which suffered such a wound fighting a conspecific. It is hardly surprising, they are called Maniraptora for a reason, and in fact members of this clade show unique adaptations to effectively use their arms while hunting or fighting, having longer forelimbs and the ability to breath freely while using them.
As for Yutyrannus and Allosaurus, a struggle based on a face-biting wrestling seems the more likely to me, with only marginal use of the arms. The one with the stronger bite would have better control of the opponent, which can prevent retaliation like you guys said, while the one with more serrated teeth would inflict more severe wounds. We just don't know enough about Yutyrannus to tell which one would have those advantages.
I found this interesting about the arms vs head matter:

http://translate.google.com/translate?u=http%3A//theropoda.blogspot.it/2008/10/perch-il-braccio-di-tyrannosaurus-non.html&hl=en&langpair=it|en&tbb=1&ie=UTF-8
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Bandog
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Was there not a fossil of allosaurus that appeared to have tendon damage on its forelimbs. I remember reading that somewhere. If I am remembering correctly then it could indicate that forelimbs see heavy use in the lifestyle of the animal, potentially in intertheropod fights.
Though ultimately I think face biting is most likely. I disagree with theropod regarding how damaging they are. A sufficiently strong bite could neutralize the head by crushing the end of the snout whereas a bite designed more for tearing does need to hit some major blood vessels to do critical damage.
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Vobby
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About face biting in general, this is pretty exaustive:

http://s3.amazonaws.com/academia.edu.documents/30190923/Tanke___Currie-1998-theropod_head_biting_behaviour.pdf?AWSAccessKeyId=AKIAI5BFST3KI667TFIQ&Expires=1383245355&Signature=VdPDYS5rhmK3Qa

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theropod
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Well, I don't think either of these two is really adapted for jaw grappling and head-biting anyway, so I also doubt such an animal would attempt it and engage in it in the same way as an animal that is (ie. lock jaws and try to wrestle with the other in a way producing high torsional and lateral loads).
Most theropods are built for quick slashes, not this kind of behaviour, and I think that's also consistent with the evidence seen in Sinraptor dongi. Komodo dragons or falcons, not crocodiles.

Rothschild et al., 2001 report stress fractures and tendon avulsions on the forelimbs of Allosaurus (as being much more frequent than in Albertosaurus or Ornithomimus, ie. more frequent than in animals whose forelimbs likely had no or no important role in predation) and interpret them as signs of predatory behaviour. Another well known pathology is the torsional fracture of in Big Al's manus.
There are also many mentions of claw marks on sauropod bones, tough not necessarily from the manual unguals.

Animals that didn't really use them for anything would not develop such strong arms and claws exceeding 25cm in lenght. The jaws are the main killing tools, but the forelimbs retain their use in prey aquisition.

Thanks!
Edited by theropod, Nov 1 2013, 11:51 PM.
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Vobby
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theropod
Nov 1 2013, 09:44 PM


Animals that didn't really use them for anything would not develop such strong arms and claws exceeding 25cm in lenght. The jaws are the main killing tools, but the forelimbs retain their use in prey aquisition.
To me, is more likely that the preys were taken by the mandibles, pulled near to the body, catched with the forelimbs, it the theropod in question had usable ones, and then bitten again. I think is just normal, all non maniraptoran theropods would reach averything, preys or rivals, with their mouth first. I actually didn't know about those injured arms, that's very interesting! But I remember reading also something similar about Tyrannosaurus arms, I'll try and find it again.
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Vobby
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Here:
http://books.google.it/books?hl=it&lr=&id=5WH9RnfKco4C&oi=fnd&pg=PA167&dq=tyrannosaurus+arms+pathology&ots=06bMU21MQr&sig=SGAqC70ja_uVbXjv42FX2nTp0Jw#v=onepage&q=tyrannosaurus%20arms%20pathology&f=false

And here:
http://books.google.it/books?hl=it&lr=&id=mgc6CS4EUPsC&oi=fnd&pg=PA90&dq=tyrannosaurus+arms+pathology&ots=387uaR6H4v&sig=6A4w6dH6ml18Y12UapAaY-svIuA#v=onepage&q=tyrannosaurus%20arms%20pathology&f=false

Seems like even T. rex used its forelimbs to hunt. It's quite ridicoulous to imagine...
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theropod
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The statistics seem to indicate this is much more common in non-tyrannosaurines, and also the more gracile arms of Tyrannosaurus etc. would require far less force to break. I remember Hartman once stating he tought this was simply due to the small arms on such a large animal naturally experiencing stresses.
I wouldn't conclude T. rex used its arms in hunting, at least not normally, they lack the morphological adaptions like well-developed manus and unguals (instead they are atrophied), but they may have had some other purpose that still required them to excert some amount of force. Both a purpose for standing up from a resting position and for mating make sense.

I agree a carnosaur would preferrably first prey with the jaws and then afterwards use the arms to clutch onto it, tough It seems Allosaurus would have the capability to reach something in front of it with the arms.
However the mouth as a grappling tool doesn't make much sense. While with the blunter, peglike teeth of a tyrannosaurine the resulting force could be utilised for gripping quite well, its likely when something tried to pull free from a carnosaurian jaw, it would just tear through its own tissue caught in the jaw.
This, and the mechanical properties of their skulls, is probably the reason for the retainment of large, hooked foreclaws in carnosaurs and other highly ziphodont theropods not adapted for holding onto animals with the jaws, but their loss in tyrannosaurines and abelisaurids, which were.
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Vobby
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I find unlikely that T.rex used its forelimbs to stand up, it couldn't pronate its hands, for example, and I don't see the mechanical necessity to use something else of the hind legs. If it needed something more, well, why not use the head and neck? Much more strong and robust.
About the mating hypotesis, it seemed likely to me, until I realized that abelisaurids could mate also without using forelimbs, so I guess is possibile for an animal with that body plan to mate without using forelimbs. But again, if it needed to get a hold on its partner, why not using the jaws? Some sharks do it after all.
Anyway, when I imagine a T. rex using its forelimbs to hunt, I just figure a fast clutch, used just to strenghten a little an already firm hold.

...but, doesn't already exist a thread to discuss theropods arms? This matter totally deserves one!
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theropod
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Using the jaws for holding a partner becomes much more difficult at the scales we are talking about. A small shark (which are the only ones we have mating footage of) can endure a bite from a conspecific without sustaining too much damage, but due to the square cube law this does not hold true for a T. rex sized one. For positioning, the arms are in quite a good position, located just underneath the chest.

I also don't think for stabilising the body when standing up they would have to be pronated, hyperextension of the manus to the sides and anchoring to the ground with the claws would suffice. In this position the biceps would contract against whatever force would otherwise propell the body forwards.
I'm not sure how you envision it using the head and neck in this matter, those would rather need to be levated as far as possible for shifting the center of mass backwards. No huge amount of force (greater than what we know the arms could endure and hold), would be needed, just enough of a stabilising effect and friction to stop it from just slipping when extending the legs.

On the other hand, for making prey contact with the arms, the neck would have to be hyperventroflexed with the snout facing downwards, which is quite unlikely for T. rex (it wasn't really much of a ventroflexor, nor particularly flexible, as we know).

You are right, this matter deserves a thread, not sure whether one exists.

Finally, something on topic: I think Allosaurian intraspecific fighting can be compared to that of baboons (when accounting for size-related problematics of course), which mainly slash at each other. While they often inflict facial injuries (consistent with the allosaurian fossil record), they rarely actually bite each other, and while they usually remain quadruped they occasionally use their forelimbs for grabbling during fights. Its highly unlikely this is their way of killing a predator such as a leopard.

Edited by theropod, Nov 2 2013, 04:45 AM.
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Bandog
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Allosaurus doesn't have the luxury of using its forelimbs to protect the head though. Baboons are able to reach out beyond their head and neck, allosaurus could not.
I think that the forelimbs are best used to complement the head, providing additional control and leverage when attacking.
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theropod
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The head would have to be pulled back to effectively use the forelimbs (and we know allosauroids, especially allosaurids were likely capable of such behaviour, since their necks are very flexible), but as I said earlier not that much for wrestling, rather keeping its own relative position to the other animal. I think faceoffs between baboons and dogs are decent analogies for allosaurid vs crushing-jawed-theropod (that is, as decent as they get).

Baboons don't seem to use their forelimbs but their gapes themselves for fending off slashes, but as I wrote, that's merely intraspecific fighting and their tactics against something they really want to kill seem to be different (here it is that we have many other good analogies). Also, if they kill, they usually do it by inflicting wounds on the postcranium (eg the tigh in one of the accounts), not biting the skull, and apparently they actually aim for the neck in their slashes.
It's thus highly doubtful allosauroids would engage in the kind of skull-biting behavioru known from Tyrannosaurines and many modern carnivorans. I'd rather envision them as a mixture of baboon, varanid and lamniform traits.

But yes, the claws could also just be used to "complement the head", by compensating for a lower bite force and teeth not built for grappling. I'm certainly not imagining a use for wrestling something down, just stabilising it and faciliating further attacks or feeding while evading attacks aimed at itself.
Edited by theropod, Nov 10 2013, 12:05 AM.
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