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Post by theropod on Mar 20, 2013 0:18:46 GMT 5
I just whished there was a picture of their reconstructions, that'd be interesting to see.
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Post by creature386 on Mar 20, 2013 1:49:02 GMT 5
I agree, but it is just a review & a summary, so their own work was only shown in second place.
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Post by theropod on Mar 22, 2013 19:57:42 GMT 5
imo new work should always be given prevalence, especially if it is really relevant, as in the case of new skull reconstructions and size estimates
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Post by theropod on Mar 25, 2013 1:04:59 GMT 5
Regarding the Density of T. rex and A. atokensis
This has led to a substantially greater mass
estimate—e.g., the density of the MOR reconstruction is 985 kg
m23 vs. 870 kg m³ for Stan and 850 kg m³ for Jane (cf. 791 and
807 kg m³ for the Sue and Carnegie specimens by VA+JM).
Hutchinson et al. 2011
Whole Body 911.63 6.912 6177.04
Bates et al. 2009 (regarding Acrocanthosaurus)
Note: by comparison their estimate for Stan was 904kg m³
Model Net Density (kg m-3) Volume (kg m2) Mass (kg)
Best estimate 933.983 1.607 1500.91
Minus 7.5% 910.648 1.436 1307.69
+ 7.5% 922.644 1.849 1705.97
+ 11.25% 928.18 1.973 1831.3
+ 15% 932.916 2.119 1976.85
Expanded rib cage 933.983 1.713 1564.44
Contracted rib cage 949.792 1.487 1412.34
Inter-vertebral spacing +0.005m 928.021 1.657 1537.73
Bates et al. 2009b (regarding Allosaurus)
It seems Carnosaurs are somewhat denser than Tyrannosaurs (something I suspected for quite some time, but merely basing on phylogeny).
in this case, Acrocanthosaurus is a whole 13% denser than sue.
It is probably save to assume Spinosaurs, being semiaquatic, where even denser.
This is interesting to see as generally people tend to say T. rex was bulkier than a carnosaur of similar lenght. It probably was, but not by much as much of its wider torso seems to have been airsacks.
You can see the same tendency even among t. rexes; sue has a wider chest than stan, but also a lower density.
Hence a T. rex with a sue-like built at a volume 13% larger than an Acrocanthosaurus would have been the same weight. It is important to keep that in mind when trying to judge body mass from visual comparisons.
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Post by creature386 on Mar 25, 2013 1:26:09 GMT 5
Interesting, so we could have been right, with our claims that Tyrannosaurus needs thicker legs/bones, because they are more pneumatic.
That also supports the idea of a high stamina in T-rex (and also may explain the wide chest in robust morphs).
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Post by theropod on Mar 25, 2013 2:05:40 GMT 5
It would be interesting to see leg bone crossections of some theropods compared. In any case, circumference isn't viable without considering pneumatisation.
I guess the wide chest might be an adaption specifically to enlarge the air sacks, what do you think?
Some info on theropod respriration would be apreciated!
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Post by creature386 on Mar 25, 2013 12:16:43 GMT 5
Well, I don't think it only had larger air sacks.
I still defend the 8 t estimate for a reason.
Henderson (1999) excluded the lung volume when estimating the mass of Tyrannosaurus. He got 7,2 t. He also explained a robust morph would weigh 500 kg more. That commonly cited as 8 t. I think his method is reliable for T-rex, as it is often cited (it is not miscited, I saw the table).
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Post by Grey on Mar 25, 2013 14:16:49 GMT 5
Interesting the pneumatic part. However I did not see it had a significant impact on the total weight of the animals in any work. Seems like it varies depending the individuals, not depending of the ontogenetic stages as Jane is situated between Stan and Sue and the holotype.
Likely linked to the facts that coelusaurs, so tyrannosaurs, are more bird-like than carnosaurs.
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Post by theropod on Mar 25, 2013 16:25:07 GMT 5
Oh, it does have significant impact on the weight. imagine the difference between a sue at a density of 807kg/m³ and one at 911kg/m³, and your 9,5t sue is suddenly 10,7t.
I'm not saying that it only had larger airsacks, but I think that can help explain much of the differences, like femur circumference and the wider chest, and it is important to keep it in mind.
From what I saw, sue, the bulkiest T. rex, is also the most pneumatic. On the other hand, allosaurus, the most slender animal here, s the least pneumatic, so there might be some degree of correlation.
It would be interesting to see a similar measure applied to Aerosteon, or at least some way to compare it to any of the animals listed above, as this is a Carnosaur well known for extreme pneumatisation.
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Post by Grey on Mar 25, 2013 17:25:39 GMT 5
For sure, but there are others factor to take in mind when talking about tyrannosaurids, with their very specific morphology.
Wouldn't be safer to compare pneumatics between tyrannosaurs specimens and not with allosaurs ?
Among rexes I see no correlation as a juvenile has less pneumaticity than Sue but more than Stan.
However, the part about the femur circumference is interesting, it reminds me the comparisons between cartilaginous and bony skeletons in fishes, the less dense cartilage allowing chondyctrians to reach larger sizes than their bony counterparts.
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Post by creature386 on Mar 25, 2013 17:36:04 GMT 5
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Post by theropod on Mar 25, 2013 18:05:48 GMT 5
@creature: I know, and its not very surprising given the degree of pneumaticity in flagellicaudatans. Grey: I meant to compare it among all theropods, not just carnosaurs and tyrannosaurs, but I didn't have data on the density of non avetheropod theropods I also wrote that we could expect the density of semiaquatic spinosaurs to be even higher. We can probably there is some degree of correlation among adults. In different ontogentic stages it is a different story. juvenile theropods are known for vastly different proportions, so the pneumaticity is likely different too. In janes case, it might not even be a T. rex, so that's not ruling it out. that cartilage thing is interesting. Can you recommend me some literature about it? It is strange, because usually weight doesn't play much of a role in the water, does it? Also, whales have bony skeletons and yet reach gigantic sizes, even larger than chondrichtyes. So that might be something specific about the built of actinopterygians. |
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Post by Grey on Mar 25, 2013 18:14:49 GMT 5
No litterature about it, I've read about it in some pages and especially from one of my discussion with Bretton Kent.
Whales are subject to other factors to have grown beyond the limits of fishes...
But restricted to fishes, you can remark a massive disparity in sizes between bony and cartilaginous. The cartilaginous skeleton is not alien to this.
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Post by theropod on Mar 25, 2013 18:26:50 GMT 5
"Fishes" don't actually exist as a natural taxon, that's why usually it is written as "pisces"
In sauropods the same seems to hold true, the largest ones sprobably where the most pneumatic ones (see SVPOW, there is a post with that title). Obviously, that's not the case with theropods, and generally among animals marine ones are the densest of them all (and overall, elasmobranchii are pretty dense as well, due to their huge liver, aren't they?).
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Post by Grey on Mar 25, 2013 19:05:15 GMT 5
The liver is massive among them. One of the largest white sharks caught had a liver about 400 kg...
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