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Post by theropod on Jul 8, 2013 15:51:46 GMT 5
When I first read the post, I thought of several people would dispute this. For now I have 4/5 right. theropod: what makes you think that T. rex would be less dense? Because of some publication where the author pointed on that large rexes were more pneumatized than carnosaurs, given their closer links with birds. The link to birds has nothing to do with that, don't you remember anything I wrote on the density issue earlier? It is the modeling of airsack sizes in the studies, plus the fact that Tyrannosaurus is highly pneumatic, apparently more so than carnosaurs usually are. The likelyhood to find a large individual in 30 specimens is logically 15 times greater than in 2. This isn't even a matter to debate. The "Sue" of Giganotosaurus is probably not yet discovered. It took many decades to find a T. rex as large as Giganotosaurus, and even then this is far from certain as I demonstrated earlier. creature386: I know it is a rigorous estimate, probably the best so far and certainly the most useful, since we have the volumetric figures for two mostmlikely quite accurate renditions.
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Post by theropod on Jul 8, 2013 15:59:47 GMT 5
I'm sorry, but I cannot see much logic in here: 3.bp.blogspot.com/-8luMvJbw664/UdiBysmqHFI/AAAAAAAAE4U/qWcy4ytYvn0/s640/spinosauri+copia.jpgThe baryonychines he uses for reference are scaled to be much smaller than the Spinosaurus snout, so no wonder he can fit the dentary when comparing to their dentary lenght. Besides, regardless of the exact percentage MNSN is bigger (which remains difficult to crossscale and also depends on the lenght of), let's recall even the holotype when scaling by the vertebrae should be much longer than the lenght cau gives even for MNSN. and I find it rather unlikely a supposedly far more mature individual would not also be bigger.
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Dakotaraptor
Junior Member
Used to be Metriacanthosaurus
Posts: 193
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Post by Dakotaraptor on Jul 8, 2013 16:12:13 GMT 5
There is not such thing as "Sue" of Giganotosaurus. There is not evidence that there must be giant Giganotosaurus bigger than two known specimens. Same with about Tyrannosaurus, not enough evidence that something is bigger than FMNH PR2081 due lack of reliable sources and fossils.
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Post by theropod on Jul 8, 2013 16:18:38 GMT 5
Not evidence. Certainities or probabilities have never been the same as evidence, nor treated as such, and you must not confuse these things. That's why we usually resort to other tactics of comparison, but still we don't directly compare the largest in 30 to the largest in two when we want to compare two species.
You have to keep this in mind when comparing them, the sample and hence the chance to have found a truly big individual is much bigger in T. rex. Hence sue is likely a bigger individual relative to the rest of the population than any Giganotosaurus specimen yet found. Hartman noted that himself, and no further evidence than basic maths is needed here.
Comparing largest to largest is just like comparing smallest to smallest. Let's see how MUCPv-ch1 compares to B-rex, which is listed as 10,4m long in the theropod database (likely still overestimated since all the T. rex-lenghts there are overestimated based on the obsolete assumption about vertebral count--it should be about 10m) and has a 1,07m femur...
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Post by Grey on Jul 8, 2013 16:29:58 GMT 5
This is impossible to say precisely how many larger specimens in both species there were, and how much they were larger. Like infers Hartman, we cannot establish which species was larger (and in all likelihood, if there was a larger one, this was probably not by much). There's no point at discussing this at length, everyone got the point.
Let's focuse on the available specimens.
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Post by creature386 on Jul 8, 2013 17:13:33 GMT 5
You guys have to remember that Hartmann does not think rexes larger than Sue are impossible: Let's move beyond just T. rex, to a question I think I've been asked a jillion times - who was bigger between T. rex and Giganotosaurus? Well, looking at what is missing in the tail of Sue and the Giganotosaurus type specimen it's clear that we really can't be precise enough to know which was longer.
I would think Sue would be heavier, since tyrannosaurs seem to have had broader torsos. The large isolated Giganotosaurus jaw suggests a bigger animal than Sue (assuming it wasn't just a Jay Leno-type individual with a disproportionately larger chin), but there are fragments of T. rex specimens that also suggest significantly larger specimens.
So I think the only reasonable conclusion here is that we simply don't know whether T. rex or Giganotosaurus got larger, but they are both freakin' huge! I don't want to say he is right (I don't believe there are larger known specimen than Sue), but I believe that some of them at least reached Sue's dimensions.
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Post by Grey on Jul 8, 2013 17:20:47 GMT 5
Creature, even excluding the very fragmentary specimens (that Hartman only suggest as possibilities of very larger sizes), the point is that in the case of both animals, undiscovered larger (but how much larger ?) specimens may exist or have existed.
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Post by creature386 on Jul 8, 2013 17:26:12 GMT 5
I know this, I only wanted to say that he doesn't believe it is impossible. I believe UCMP 137538 (if it was a Tyrannosaurus) could have been as large as Sue. In both animals, there could be larger specimen, but in Tyrannosaurus, we have a better idea of average sizes.
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Post by Grey on Jul 8, 2013 17:36:36 GMT 5
I know this, I only wanted to say that he doesn't believe it is impossible. I believe UCMP 137538 (if it was a Tyrannosaurus) could have been as large as Sue. In both animals, there could be larger specimen, but in Tyrannosaurus, we have a better idea of average sizes. That's totally true. For speaking with a paleontologist recently about that, he explained a sample of 30 individuals is the minimum for establish a beginning of average sizes in a population. But is there some publication about the average size in rex population ?
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Post by creature386 on Jul 8, 2013 17:42:49 GMT 5
I don't believe there is any.
P.S. When he said 30 is the minimum, was he speaking about animals of all age classes or only adults?
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Post by Grey on Jul 8, 2013 17:57:27 GMT 5
Not precised but I guess he counted adults, even if the knowledge of growing size in youngsters may also help.
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Post by theropod on Jul 8, 2013 19:01:48 GMT 5
I'm gonna make another try of cross-scaling MUCPv-ch1 and MUCPv-95.
And I'd like to note in Bates et al, the narrower the body (BHI 333-Acrocanthosaurus atokensis-MOR 555-MOR 693), the higher the pneumaticity. The same is also seen in Hutchinson et al. I think what those broad-chested specimens have in bulk was air for a good part. Hartmans results when accounting for the density I assumed are actually surprisingly similar to my earlier guesses.
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blaze
Paleo-artist
Posts: 766
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Post by blaze on Jul 8, 2013 19:43:43 GMT 5
Hartman already warned about the shortcomings of volumetric models based on mounted skeletons.
Relevant quotes:
The picture that is painted is that pnumatisation is more developed in larger taxa, not just those that have a wide torso. Stan had a density almost equal to Fran in Bates et al. (2009) and MOR 555 was just marginally above that. As I previously said in cf, the higher density of MOR 555 in Hutchinson et al. (2011) could be not only to the mount having a torso that's too small (in length, not just width) but the lower resolution of the scans compared to those for the other specimens, IIRC they said this oversized the head in the models among other things, this could be the main reason of those results because Bates et al. (2009) didn't find such stark difference to the other theropods. There's nothing proving that had Fran (the largest Acrocanthosaurus) been included in Hutchinson et al. (2011) it wouldn't ended up with a density similar to the Tyrannosaurus just like in Bates et al. 2009.
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Post by theropod on Jul 8, 2013 19:54:23 GMT 5
Which would still make it denser then FMNH PR 2081. Also, what about the density of Allosaurus?
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Deleted
Deleted Member
Posts: 0
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Post by Deleted on Jul 8, 2013 20:05:48 GMT 5
Using the GDI method I arrived at about ~502.96 liters for the head of CM 9380. I'll calculate the rest of the body soon. EDIT: Nevermind, I did it wrong, the slices were not equally spaced
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