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Post by coherentsheaf on Dec 22, 2013 22:59:45 GMT 5
At first, I don't like Cau that much (or is there a rule forbiding to appreciate specialized paleontologists) ? Then, it is of course, much more cautious to claim that this A Tyrannosaurus weighed 5-8 tonnes than an exact 6 873 kg. Just based on what you say, on different methods. Cau does not rely on one estimate or one range, but on all the published reasonnable figures. You just have to read his posts for understand this. Why 5-8 and not 6-9. Giving ranges without methdology is just arbitrary. Noone is claimig that the point estimate is the exact mass Tyrannosaurus A had in life. It is however probably better than an arbitrary range pulled out of someones ass. This has nothing to do with caution: The estimated Tyranosaurus A could in fact have weighed 4500 or 8500 kg as far as we know, and the range does not account for that, while point estimates rather affirm the uncertainty contained. You are sure that it is wrong and not sure by how much. The range is in this case the less cautious method, and is just another way how the researchers bias and mistakes can influence the final expression. A similar thing happened when Siverso gave a range of 13-14m for Lyviatan. Based on variance n Physeter, Lyviatan was more likely outside this range than inside: The range was pulled out of thin air and was less correct than the point estimate. |
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Post by theropod on Dec 22, 2013 23:18:24 GMT 5
Hartman based the ribcage in his skeletal on the actual remains, including the rib Cau used.
It is entirely possible it was quite slim-bodied for an animal of such size, but that doesn't change the accuracy of this depiction, which I think is the best there is to date. The ribcage in Hartman's spinosaurus is not particularly massive, but what gives you this (correct) impression of the massive body is that the ribcage is not the only part contributing to a deep torso in Spinosaurus.
Of course the more incomplete the remains, the greater the uncertainty in the skeletal. But a skeletal can also be a simple demonstration of the results of an array of methods used to restore it. It depends on those how good it is, and I presume Hartman's methods are quite good.
At least, such a restoration will give you better insights than comparison of individual bones between phylogenetically distant taxa. It includes the information there is to gain by such a method, but at the same time also brings them into context of the complete animal's osteology.
As for the size estimate based on the latter methodology, I'm quite certain it's far too extreme. I can see the holotype might be less massive than sue, but not MNHM v4047, which is most likely a good deal larger (see the size comparison thread for the information). I myself quite like giving size ranges based on estimates, if for example there's a certain unknown that has yet to be resolved, but there has to be a purpose behind them. 5-10t is a highly vague estimate, while sue's weight can be constrained much better.
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Post by coherentsheaf on Dec 22, 2013 23:21:54 GMT 5
Hartman based the ribcage in his skeletal on the actual remains, including the rib Cau used. It is entirely possible it was quite slim-bodied for an animal of such size, but that doesn't change the accuracy of this depiction, which I think is the best there is to date. The ribcage in Hartman's spinosaurus is not particularly massive, but what gives you this (correct) impression of the massive body is that the ribcage is not the only part contributing to a deep torso in Spinosaurus. Of course the more incomplete the remains, the greater the uncertainty in the skeletal. But a skeletal can also be a simple demonstration of the results of an array of methods used to restore it. It depends on those how good it is, and I presume Hartman's methods are quite good. At least, such a restoration will give you better insights than comparison of individual bones between phylogenetically distant taxa. It includes the information there is to gain by such a method, but at the same time also brings them into context of the complete animal's osteology. As for the size estimate based on the latter methodology, I'm quite certain it's far too extreme. I can see the holotype might be less massive than sue, but not MNHM v4047, which is most likely a good deal larger (see the size comparison thread for the information). I myself quite like giving size ranges based on estimates, if for example there's a certain unknown that has yet to be resolved, but there has to be a purpose behind them. 5-10t is a highly vague estimate, while sue's weight can be constrained much better. What is you range for Sue? 7-10 tonnes? 8-9 tonnes? With what probability would you say Sue falls into this range? |
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Post by Grey on Dec 22, 2013 23:47:32 GMT 5
Once again, why not corresponding with Cau on his blog about this ? The various arguments here are interesting but I ask some direct confrontation instead of consensual claims.
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Post by creature386 on Dec 23, 2013 0:09:51 GMT 5
Hartman based the ribcage in his skeletal on the actual remains, including the rib Cau used. It is entirely possible it was quite slim-bodied for an animal of such size, but that doesn't change the accuracy of this depiction, which I think is the best there is to date. The ribcage in Hartman's spinosaurus is not particularly massive, but what gives you this (correct) impression of the massive body is that the ribcage is not the only part contributing to a deep torso in Spinosaurus. Of course the more incomplete the remains, the greater the uncertainty in the skeletal. But a skeletal can also be a simple demonstration of the results of an array of methods used to restore it. It depends on those how good it is, and I presume Hartman's methods are quite good. At least, such a restoration will give you better insights than comparison of individual bones between phylogenetically distant taxa. It includes the information there is to gain by such a method, but at the same time also brings them into context of the complete animal's osteology. As for the size estimate based on the latter methodology, I'm quite certain it's far too extreme. I can see the holotype might be less massive than sue, but not MNHM v4047, which is most likely a good deal larger (see the size comparison thread for the information). I myself quite like giving size ranges based on estimates, if for example there's a certain unknown that has yet to be resolved, but there has to be a purpose behind them. 5-10t is a highly vague estimate, while sue's weight can be constrained much better. What is you range for Sue? 7-10 tonnes? 8-9 tonnes? With what probability would you say Sue falls into this range? Theropod once gave a range of 7-8 t for Sue (on CF?). I personally favor 8 t, because of Hartman's new mass estimates. |
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Post by coherentsheaf on Dec 23, 2013 0:49:55 GMT 5
What is you range for Sue? 7-10 tonnes? 8-9 tonnes? With what probability would you say Sue falls into this range? Theropod once gave a range of 7-8 t for Sue (on CF?). I personally favor 8 t, because of Hartman's new mass estimates. That was not the point. The point was that these ranges are typically built on nothing but conjecture themselves. In any case Hartmanns estimate was 8.4 tonnes, which is in line with previous estimates all between 8 and 9 tonnes. What we can say about this: Newer volumetric methods produce estimates in this range so far. Any statement like Sue weighed between 8 and 9 tonnes is premature, for all we know it could have weighed 6 tonnes or even 11 tonnes. |
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Post by theropod on Dec 23, 2013 3:30:58 GMT 5
I tend to favour the assumption of a lower density (reasons explained earlier in this thread), but I also equally accept the possibility that I am wrong.
The two resulting figures (7.3-8.4t) that I find most likely, because they based on the imo best model (Hartman's) form my range.
As to the probability, I cannot tell anything mathematically rigorous because there are way too many variables relevant to it (and because I’m way too loosy at statistics), but it's what seems most reasonable to me. I'd say ~70-80% (but that's a guess).
Volumetric estimates have yielded estimates beteween 6.1 and 9.5t, of which I think both the extremes are not reasonable at all, but Hartman's model (the median) is quite good. If I have a certain issue that I'm not certain about, so I can express it this way.
Another example would be Saurophaganax, where the variable of humeral lenght is decisive for the specimen's size, but not cleared up so far. The resulting figures are 11.5 and 13m respectively, using certain premises which one considers most likely.
The whole 5-10t story is a different matter, considering 5t obviously is no reasonable estimate for FMNH PR2081, and Cau obviously does not think they are both just anywhere within that range. It creates an arbitrary and unnecessary imprecision.
It is not better than a point estimate (given you know how to properly interpret the latter), but in palaeobiology they mean pretty much the same, a point estimate should be the expected value--the only problem is that those estimates’ probabilities themselves are a matter of debate. A range can help giving an overview or constraining the size no more than the data allow to be done properly.
Regarding Cau, I have commented on his blog when he deduced something about relative masses of theropods based on their femur circumferences. I pointed out the problems to him (if I recall correctly in a similar manner as I usually do), and he agreed with me. He either forgot about it, or it didn't come to mind that it also applies here.
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Post by Runic on Dec 23, 2013 6:52:18 GMT 5
Why are you people not famous paleontologist yet?
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Deleted
Deleted Member
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Post by Deleted on Dec 23, 2013 15:31:05 GMT 5
he merely claims no Spinosaurus above 13m existed... He doesn't believe that anymore. Why else would he make a reconstruction of a ~15-meter Spinosaurus with the known remains? Anyway I had enough of this size argument. Cau has his opinion, shartman has his, we have ours. Cau never intended to present his notions as solid facts/the end-all. The notion that a vertebral comparison with Acrocanthosaurus would yield a result that doesn't correlate with it's overall skeletal volume makes me disagree with Cau's figures though, but he's already been fine with people disagreeing with him. He simply has a different opinion, can we just let this issue go. |
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Post by creature386 on Dec 23, 2013 16:05:06 GMT 5
Does Cau actually believe that MSNM V4047 was larger than the holotype? I know, he made a 15 m long MSNM V4047 reconstruction, but there was a blog post, where Cau said there is not enough evidence to assume that the holotype was a sub adult.
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Post by theropod on Dec 23, 2013 18:50:06 GMT 5
There actually doesn't seem to be any good evidence for the holotype being subadult. That however does not mean MNHM wasn't much bigger than it, as suggested by the majority of restorations. Cau's most recent one had it at 8% bigger if I recall correctly, but it restored it very short and with a massive underbite.
I agree with broly. However what Cau writes is often quite confusing, at the same time he can make a skeletal of a 15m Spinosaurus, claim how unrigorous skeletals of Spinosaurus were, and claim the holotype wass 12.5m with no reason why other specimens would be bigger (and present a restoration of it being bigger, even tough just slightly). I think at the moment he does not believe in any Spinosaurus exceeding 14m, since that's what his most recent comparison showed.
I must say no matter how good a resource it may be, theropoda.blogspot is so filled up with sarcastic ridicule, and often so negative and agressive it’s simply not enjoyable to read.
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Post by creature386 on Dec 23, 2013 19:03:18 GMT 5
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Post by theropod on Dec 24, 2013 2:25:29 GMT 5
Yes, that's the one I meant (the same which was also posted on our comparisons-thread)
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gigadino96
Junior Member
Vi ravviso, o luoghi ameni
Posts: 226 
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Post by gigadino96 on Dec 29, 2013 19:29:50 GMT 5
he merely claims no Spinosaurus above 13m existed... He doesn't believe that anymore. Why else would he make a reconstruction of a ~15-meter Spinosaurus with the known remains? Anyway I had enough of this size argument. Cau has his opinion, shartman has his, we have ours. Cau never intended to present his notions as solid facts/the end-all. The notion that a vertebral comparison with Acrocanthosaurus would yield a result that doesn't correlate with it's overall skeletal volume makes me disagree with Cau's figures though, but he's already been fine with people disagreeing with him. He simply has a different opinion, can we just let this issue go. He still believe in. He thinks that the Spinosaurus specimen MNSM V4047 was 55 % of the body mass of "Sue", and the already citated speciemen was 107-108 % the size of the holotype, if not less than that. Still possible, though a bit conservative.
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Dakotaraptor
Junior Member
Used to be Metriacanthosaurus
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Post by Dakotaraptor on Jan 3, 2014 17:39:57 GMT 5
I don't think MSNM V4047 was that small, my opinion is much closer to Hartman's one. However Cau's estimates are still more reliable than guestimates by amateurs/fanboys like 19-21 m or 25 m and >2 m skull. *basta*.
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