Tyrannosaurus rex vs. Giganotosaurus carolinii

[Grey]

Carcharodontosaurids are built and considered to be slower than tyrannosaurids, but they were not slow-moving predators.

[Deleted]

Sept 20, 2013 19:07:21 GMT 5 creature386 said:

Sept 20, 2013 18:34:04 GMT 5 @brolyeuphyfusion said:

2. Speed goes to Giganotosaurus, not Tyrannosaurus, based on the known scientific information

Giganotosaurus: app.pan.pl/archive/published/app46/app46-193.pdf
14 meters/second * 3600 seconds = 50,400 meters/hour or 50.4 kilometers/hour

You know that this paper only tried to calculate the maximum speed where Giganotosaurus would not fall?

This problem is out of the scope of this paper, and we will focus on whether the animal will fall or not, assuming that falling will represent a real danger.
In this predictive kinematic model of the cursorial capacity of bipedal animals we assert that the principle limitation for cursorial capacity is the maximum speed at which the biped is capable of recovering body equilibrium.

That doesn't mean this was it's actual speed, just the maximum speed where it wouldn't fall.
50 km/h for such a large biped is unlikely.

It' the only scientific info I could find about it.

I cannot calculate one unlike with size figures, and I will never make up a speed figure out of nowhere.

[theropod]

creature386: I Think you refer to the humerus midshaft width-femur-lenght correlation they used? I'm sceptical regarding the reliability (they also use femur-circumference-formulas to derive their mass estimates).
It is also hardly likely there is no variation in humerus midshaft widths depending on the theropod and how robust it's arms are, this one may simply have had robust humeral midshafts (which is actually the case, compare it to the humerus of Acrocanthosaurus which displays the approximate ratio of what their calculation yielded. That of Mapusaurus is a visibly broader structure).
Sue for example has a humerus with a midshaft width of 56mm, which is only 84% of the width a Mapusaurus of supposedly equal humerus lenght has.

The difference between this figure and Acrocanthosaurus at equal femur lenght (and it has to be keept in mind Mapusaurus may have longer femora relative to lenght) is short of 14%, hardly a difference that could not be the result of the observable shape variation.

But the big difference between Tyrannosaurid and Carcharodontosaurid forelimbs is not as much in their humerus lenghts as in the lenght of antebrachium and manus, and the robusticity of the whole structure.

How is their relationship supposed to work? I tried using it and the results were completely off.

(y= 0.82x – 0.81,
r² = .92, where y is the logarithm of femur length,
x is the logarithm of humeral shaft width, and r2
is the correlation coefficient)

Could someone please clear that up, since it is of utmost importance?

[theropod]

Sept 20, 2013 20:23:00 GMT 5 Grey said:

Carcharodontosaurids are built and considered to be slower than tyrannosaurids, but they were not slow-moving predators.

Who said that actually? Not meaning to disagree with it (it's logical after all, unless we are talking about an extremely heavy T. rex), but "considered" implies this was stated by someone.

[creature386]

Sept 20, 2013 20:51:41 GMT 5 @brolyeuphyfusion said:

Sept 20, 2013 19:07:21 GMT 5 creature386 said:

You know that this paper only tried to calculate the maximum speed where Giganotosaurus would not fall?That doesn't mean this was it's actual speed, just the maximum speed where it wouldn't fall.
50 km/h for such a large biped is unlikely.

It' the only scientific info I could find about it.

I cannot calculate one unlike with size figures, and I will never make up a speed figure out of nowhere.

I didn't want to make up a speed figure for Giganotosaurus, but we can't assume that it was faster, because of two speed estimates which are based on completely different methods (one refers to the actual maximum speed and the other one to the speed where it could keep it's balance).
All the arguments limiting the speed of Tyrannosaurus, could be easily used for Giganotosaurus as well:

Our model thus strengthens the conclusion that T. rex was not an exceptionally fast runner, and supports the inference that more upright (although not completely columnar) poses are more plausible for T. rex. These results confirm general principles about the relationship between size, limb orientation, and locomotor mechanics: exceptionally big animals have a more limited range of locomotor abilities and tend to adopt more upright poses that improve extensor muscle effective mechanical advantage. This model builds on previous phylogenetically based muscle reconstructions and so moves closer to a fully dynamic, three-dimensional model of stance, gait, and speed in T. rex.

www.rvc.ac.uk/SML/People/jhutchinson/documents/JRH17.pdf
Giganotosaurus is also "exceptionally big".

There are also sources which claim Tyrannosaurus to be faster, because of the femur/tibia ratio. This is just as questionable.
I would wait until a paper compares both. For now, I would assume roughly equal speed. I can't think of an anatomical adaptation what would make Giganotosaurus faster (except for being more slender, but they are roughly equal in weight, so I doubt this would change a lot).

Sept 20, 2013 21:00:38 GMT 5 theropod said:

creature386: I Think you refer to the humerus midshaft width-femur-lenght correlation they used?

I am referring to the stament of Mapusaurus humerus being 1/4 as long as it's femur and the one of Acrocanthosaurus being 1/3 the length of the femur.

Even without that, it looks like the humerus of Acrocanthosaurus was longer. It's humerus was 370 mm long (you can look at the table 1 in the Fran description paper), while the one of Mapusaurus is believed to be 300 mm long. You could of course argue that the length of the Mapusaurus humerus is estimated and the rest of the forelimb could be a lot longer than in Acrocanthosaurus, but I would work with what we have.

[creature386]

BTW, there is also a positive relationship between humerus length and forelimb flexibility/strength. You can read Ursus arctos' posts on carnivora regarding bear forelimb flexibility/strength.
So, even if the forelimb of Mapusaurus (or Giganotosaurus, assuming similar proportions) was overall larger, it still won't be as useful, because of the limited flexibility/strength.

[theropod]

creature386: That was based on that formula, which was used to determine a fitting femur lenght. That femur lenght btw was also smaller than that of Acrocanthosaurus (supposedly 118cm vs 128cm).
I've tried to scale Mapusaurus' humerus visually from Acrocanthosaurus, but their distal ends are very different in shape, making that near-impossible, even tough this would be very useful.

I doubt the same that applies to a quadrupedal bear can be applied here, and usually flexibility and strenght are not positively correlated at all.

Regarding the speed of both: I assume based on the limb proportions (elongate distal elements) without inclusion of varying estimates for the body weight Tyrannosaurus is the more cursorial animal, and would probably be faster on average (Sue if it was ~7-7,5t or most other specimens with comparatively longer legs, such as CM or AMNH). However in case we are using a 8,4t Sue vs a 8,2t Giganotosaurus, Sue has considerably shorter legs relative to it's bulk, so in that case it's pretty questionable. That this doesn't necessarily relate to maneuverability or acceleration should be clear to everyone.

[creature386]

The humerus of Mapusaurus is fairly complete:

Most of a right humerus (MCF-PVPH-108.45) of Mapusaurus n. gen. was found, lacking only the bone proximal to the deltopectoral crest (Fig. 22).

www.mnhn.fr/museum/front/medias/publication/7653_g06n1a4.pdf
So I doubt their number is too far off.

Also, I don't see what's wrong with the larger animal having a shorter femur. Sue is also larger than the Giganotosaurus holotype, yet it has a shorter femur.

[Grey]

Sept 20, 2013 21:09:39 GMT 5 theropod said:

Sept 20, 2013 20:23:00 GMT 5 Grey said:

Carcharodontosaurids are built and considered to be slower than tyrannosaurids, but they were not slow-moving predators.

Who said that actually? Not meaning to disagree with it (it's logical after all, unless we are talking about an extremely heavy T. rex), but "considered" implies this was stated by someone.

I know since years a Belgian paleobiologist not specialized in carcharodontosaurids in his works but total fan of carcharodontosaurids, especially Giganotosaurus about which he did extensive research and contacts with various theropods specialists like Coria, Currie, Rahaut... I discussed of Giganotosaurus with him earlier this year and that's pretty much what he said in one of these discussions.

[theropod]

Sept 20, 2013 21:54:25 GMT 5 creature386 said:

The humerus of Mapusaurus is fairly complete:

Most of a right humerus (MCF-PVPH-108.45) of Mapusaurus n. gen. was found, lacking only the bone proximal to the deltopectoral crest (Fig. 22).

www.mnhn.fr/museum/front/medias/publication/7653_g06n1a4.pdf
So I doubt their number is too far off.

Also, I don't see what's wrong with the larger animal having a shorter femur. Sue is also larger than the Giganotosaurus holotype, yet it has a shorter femur.

The proportions in Carcharodontosaurs (eg. Acrocanthosaurus-Giganotosaurus) do not support that, that's all. Individual variation is of course plausible, but then it can be expected not to affect the humerus lenght.

I'm not saying their number is far off, it probably isn't.

[creature386]

I now understand what you mean, but femur length is irrelevant here.
Thanks for clarifying that though.

[theropod]

Any idea how the formula works?

[Dakotaraptor]

50 km/h seems to be very overestimated compared to speed estimates from newer papers. Even it was before "speed limiting" which has been since 2002. And no papers stated speed estimates of over 40 km/h for Tyrannosaurus itself and other giant theropods after 2002, but = or < 40 km/h.

Although i suspect Sellers's and Manning's speed estimates (29 km/h for 6 metric ton T. rex) may be slightly underestimated because they are only based on estimates of leg muscles, ignoring tail and perhaps hip muscles.

They were probably fast animals, but not as fast as they used to be considered one or two decades ago. 

[theropod]

for their size they are certainly fast, dynamic animals. there are few, if any, animals that size with a non-collumnar and mainly graviportal leg structure. In contrast, large theropods (some more than others) display elongate, slightly flexed, slender hindlimbs.
I suppose the fact that they were hunting either very large or reasonably fast creatures made this necessary.


I personally think 40kph for T.rex (altough perhaps not sue itself) could very well be true, based on the adaptions we can see and the many supposedly rather quick prey species (hadrosaurs, ceratopsians; both supposedly at least asfast as elephants).

[wiffle]

You realise size is perhaps the most important factor in any fight?

Weight, no. For brawlers that are incapable or have difficulties attaining quick kills, bodily strength is relevant, but it matters almost nothing here.

Is there any evidence for that?

That size comparison I posted. For Giganotosaurus to use its claws while both are in a normal posture, its head, neck, and shoulders would have to warp right through Tyrannosaurus. Even if it reared up, the arms could not reach very far, and any contact would do minimal tissue damage.

"theropods have limited range of motion in their arms

That's because they do. Tyrannosaurus, I think, had a range of motion of only 40 degrees, and probably could not extend its arms outwards at all (although the effectiveness of such an action if it were somehow possible would be laughable).

Toppling gets more dangerous with increasing weight, so I don't see the relevance of this observation.

Pushing someone over is a lot easier if they are lighter. Regardless it really doesn't matter much\.

numbers 1, 2, and 4 would hardly matter at all

Bite force and speed don't matter now?

Bite force=Quicker kill and much less time to retaliate, whereas speed reduces the window of time to react and counter a charge, and could also prove handy for running away if Tyrannosaurus ever needed it.

3 is indeed miniscule by your own words

When did I saw that?

Granted it is not a huge advantage, but it is nevertheless more important than a few hundred pounds for an animal that may not even make bodily contact with its opponent. Depth perception aids in Tyrannosaurus' primary mechanism of attack, which can't be a bad thing.

there is no evidence for 5, which could just as well be the other way around.

The fossil record indicates that intraspecific fighting was common within Tyrannosaurus.

Experience an animal has in hunting a Triceratops helps as little with fighting another theropod as experience with hunting a sauropod

Doing battle with a Triceratops should require faster reflexes than fighting a sauropod. It's like fighting an elephant versus fighting a whale-the elephant is better suited for combat and is faster and more agile, whereas the whale is extremely powerful and can take out just about anything with a single swipe but has numerous exposed areas and a limited degree of accuracy.

tooth-sharpness

You mean to say that the point on this:

Versus the point on this:

Is somehow supposed to overcome:

You'll forgive me for doubting you.

striking speed

Any evidence for that?

which are just as important

...

Bite force isn't an advantage by itself,

How? A higher bite force is never a disadvantage.

Dentition matters more than bite force, and a crushing bite is not deadlier than a slicing one.

It is when the bite force is about 6 times higher.

There's nothing to suggest Tyrannosaurus' teeth couldn't slice, albeit less effectively.

Sharks have a slicing dentition and a relatively low bite force

Great white sharks actually have a fairly significant bite force, well in excess of 1 ton at the posterior jaws.

Furthermore, it is silly to suggest that even Giganotosaurus' teeth have the slicing potential of a shark's.

Also, komodo dragons have quite low bite forces, but their bites still cause severe damage due to dentition and mechanical advantage

Studies into the komodo dragon's bite force didn't take neck muscles into account.

mechanical advantage in the jaws

So do you suggest Giganotosaurus will have any advantage in that area?

Speed goes to Giganotosaurus, not Tyrannosaurus, based on the known scientific information

Creature386 already cleared the first study up. You only have to look to see that Tyrannosaurus' hips allow for much more muscle attachment. The leg proportions are also more cursorial, and according to Persons and Currie, "...the mass of the M. caudofemoralis was further increased by dorsoventrally lengthening the hemal arches." With that being said, given both the weight and caudofemoralis studies I would not be surprised if Tyrannosaurus' speed were more in line within the 21-22 mph range.

3. Vision is not really an advantage in a face-to-face fight unless one combatant is blind

How is it "not really an advantage"? Greater depth perception helps gauge distances and therefore informs Tyrannosaurus more precisely on the matter of exactly how fair it has to charge/lunge to attack, and how much it needs to move to counter or dodge. I would imagine that people would be much more comfortable with Tyrannosaurus' vision than Giganotosaurus' if they were involved in a fight.

maneuverability

Tyrannosaurus likely has the edge in this field. As Persons and Currie explain:

In the genus Tyrannosaurus, the mass of the M. caudofemoralis was further increased by dorsoventrally lengthening the hemal arches.

Because the M. caudofemoralis is the primary hind limb retractor, large M. caudofemoralis masses and the resulting contractile force and torque estimates presented here indicate a sizable investment in locomotive muscle among theropods with a range of body sizes and give new evidence in favor of greater athleticism, in terms of overall cursoriality, balance, and turning agility.

www.ncbi.nlm.nih.gov/pubmed/21157923

Although i suspect Sellers's and Manning's speed estimates (29 km/h for 6 metric ton T. rex) may be slightly underestimated because they are only based on estimates of leg muscles, ignoring tail and perhaps hip muscles.

I think it's a fair bit more than "slightly" considering that Tyrannosaurus' hips and tail both seem to be major contributors to its mobility.