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Post by theropod on Oct 13, 2015 22:07:06 GMT 5
This is an oxymoron. "A mass far superior to a sperm whale of the same size is an upsizing."
In absolute terms the mass is comparable to a sperm whale, marginally lower than the only mass figure published. I was under the impression that when talking about size, we are referring to mass, not length, but very well. Even if you arbitrarily change it, the same applies to length; my length estimate certainly isn’t higher than that already proposed for Livyatan in the literature, and not higher than Physeter.
And I don’t understand why it is so hard to understand that if 57t is the only published weight figure for an animal, an estimate of 56t does not constitute an upsizing of its mass.
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Post by Grey on Oct 13, 2015 22:15:09 GMT 5
57 tonnes at 17.5 m not at 15.4 m like your model.
The 57 tonnes body mass at 17.5 m suggests 31 tonnes at 15.4 m but you suggest 56 tonnes.
You version of Livyatan, not the specimen but the species, is much bigger than normally expected.
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Post by theropod on Oct 13, 2015 22:31:47 GMT 5
(15.4/17.5)^3*57=39≠31 just like 3≠6 and 57>56
And their estimate happened to not be 15.4m, it’s irrelevant what it would weigh when isometrically scaled down to that length.
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Post by Grey on Oct 13, 2015 22:41:50 GMT 5
Typo, I meant 39 tonnes.
If they estimate Liv 57 tonnes at 17.5 m, it is obviously lighter at 15.4 m than your model. Your model is bulkier, heavier,bigger.
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Post by elosha11 on Oct 14, 2015 21:39:15 GMT 5
theropod, I too think that thick soft tissues of kogia can possibly make kogia's body look more streamlined. However, In my opinion, this can be more fundamental factor; < source: www.skullsunlimited.com/record_variant.php?id=3991 > Above: replica of Kogia skeleton Below: CT scan of an entire Kogia < www.whoi.edu/services/communications/oceanusmag.050826/images/v43n2-ketten5en.jpg > < www.whoi.edu- >
As far as I know, like this kogia specimen, whale's ribs are usually folded or at least slightly bended while whale is underwater in order to endure water pressure. so despite their actual skeleton is deep chested, since ribs them selves literally collapse(which shrinks chest area dramatically and make overal body more streamlined and more clindrical shape), the whale's overal body dose not shows up their "deep chest".
So IMO this can explain why many whale's skeletons are bulky and deep chested despite actual whales themselves are rather slenderer or more streamlined.
Thanks for that, this is the point I was trying to make and your pics seem to better confirm it. The ribs are collapsing/contained more tightly within the the body of the animal which is the skeletal mounts appear to be inaccurate, and why the pgymy is not nearly as rotund and bulky as the mounts would suggest. I think such inaccuracies might also apply to the Brygmo skeletal cast.
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Post by Infinity Blade on Nov 22, 2015 6:47:52 GMT 5
^That is among the most laughable pages I've ever read, using intelligence and tooth lenght as key advantages, not even taking into account jaw structure and function, and making Livyatan a sluggish behemoth in exchange. Old comment, but I have a question. How relevant do you think tooth size is in comparison to other bite potency factors (e.g. dental morphology, jaw morphology, postcranial motions, jaw/head size, tooth distribution, bite force, etc.)? It's not really at all among the most important, is it?
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Post by theropod on Nov 22, 2015 15:54:48 GMT 5
I think asking about the relevance of those individual factors is pointless, none of them is of any use on its own, and they are all measured differently. For some of those, there isn’t even a "better" or "worse".
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Post by Grey on Nov 22, 2015 21:28:20 GMT 5
The study about Livyatan bite will be interesting.
For now we have evidences of devastating bite damages and bite force in megalodon and good indications of this in Livyatan.
I still tend to think the shark had overall a more voluminous bite than the whale, hence a larger surface of damages.
Interestingly I should discuss with meg researchers, a blogger explained that several bite marks on some meg teeth were made when the tooth was partly dislodged.
The presence of two parralel bite marks are according to him possible indication that the rows were closely packed in megalodon, and that prey was experiencing not only one but several rows of teeth during one bite.
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blaze
Paleo-artist
Posts: 766
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Post by blaze on Nov 29, 2015 10:14:53 GMT 5
So, I used the 3rd supplement of Lowry et al. (2009) to get an idea of circumference of the upper tooth row of a 17.9m C. megalodon, the result was 304cm and 194cm in diameter if presented as a semicircle, this is interesting because in the simple reconstruction I made, if scaled to 17.9m long, it has an upper tooth row as measured in a lateral view of at least 1.1m, add the other side and we get a flat width of 2.2m but what about the width of the jaws? how much would that increase the measurement? I don't know but I think it is clear that the head in my reconstruction is too big by no less than 13%, perhaps over 20%.
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blaze
Paleo-artist
Posts: 766
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Post by blaze on Nov 30, 2015 5:58:12 GMT 5
I'm thinking, what is the basis for C. megalodon having a body depth 25% of fork length? the largest living sharks are much more streamlined (~13% based on photo of a whale shark) and fast whales (fin whales) are much more streamlined and shallow bodied than slow whales like the right whale, the fastest bony fishes are also shallow bodied, is there a good reason for such deep body? or is it just another extrapolation from the trends in the great white shark just like the pug-nose that BK criticized?
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Post by theropod on Dec 1, 2015 0:39:39 GMT 5
It’s certainly an extrapolation (what else would it be?), the question is whether it’s based on quantifyable data or rather artistic license (as the jaws apparently are). If you take the available regression equations ( sources→) and compare the extrapolated mass for a 14m megalogon to a hypothetical isometrically scaled 5m great white, this is what you get. c(5, 14)->a c(3.29*10^-6*(100*a[1])^3.174, 7.5763*10^-6*(0.9442*(100*a[1])-5.7441)^3.0848, 4.80376*10^-6*(100*a[1])^3.09497, 7.914*a[1]^3.096, 3.8*10^-6*(100*a[1])^3.15, 10^0.99*a[1]^3.00)->avg c(3.29*10^-6*(100*a[2])^3.174, 7.5763*10^-6*(0.9442*(100*a[2])-5.7441)^3.0848, 4.80376*10^-6*(100*a[2])^3.09497, 7.914*a[2]^3.096, 3.8*10^-6*(100*a[2])^3.15, 10^0.99*a[2]^3.00)->max mean(max)/(mean(avg)*(a[2]/a[1])^3)
>mean(avg) [1] 1195.441 >mean(max) [1] 29255.23 >mean(max)/(mean(avg)*(a[2]/a[1])^3) [1] 1.114811
In this scenario, the megalodon is ~11.5% bulkier than a great white. Assuming that this increase is spread equally between body depth and body width (whether it is in fact is an interesting question), we just have to take the sqrt() of that to get that it would be expected to be 5.6% deeper-bodied than a great white. That’s what the allometry of great white sharks implies. No doubt you can vary this by a few percent, for example, if instead of an average 14m megalodon you use an 18m one (c(5, 18)->a), the result is 14.5% bulkier than the 5m great white, and would be expected to be 7% deeper-bodied. It always depends. And if C. megalodon was anything like a great white, then we can expect to see a wide scope of variation, but the question should be what was the norm for the species, based on the norm for Carcharodon. Now, the question is, how large a percentage of fork length is body depth in a typical adult great white? The last time, when I used Compagno’s drawing and increased its bulk to account for allometric effects, the resulting proportions were criticised sharply. Perhaps that’s because Compagno (1984) depicted a freakishly slender great white and I’m just too biased to see that. Or perhaps it isn't. I do have severe problems to envision the average great white's body depth being in excess of 23% of fork lenght, which is what it would have to be. So at least before taking it as written in stone as certain people have done before, it'd be good to post some actual evidence for this depiction. Be that as it may, my suggestions on the matter aren't going to be universally welcomed here. So in any case it will be better if you, being not involved in that debate, come up with your own conclusion. It’s also worth noting that there are some deep-bodied yet very athletic aquatic animals (tuna and killer whales spring to mind).
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Post by Grey on Dec 1, 2015 1:42:21 GMT 5
I'll ask to B.K.
I think the shape is very thuna-like itself.
I m not sure it's sheer artistic license from the author, that's usually not his way to work.
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Post by Vodmeister on Dec 1, 2015 15:27:48 GMT 5
I do not believe that Livyatan was physiologically much different from a modern day Sperm Whale. Even if we assume a weight of 57 t for Livyatan, only about 38 t of that would actually be organs. About one-third of a Sperm Whale's mass is basically a storage of triacylglycerol, other fatty acids, and waxes. They use the spermacity organ to adjust their buoyancy accordingly to how deep they want to dive, or if they need to rise above the water. This is the only function of this organ, other than shear volume. Sharks do have something similar. Basically, 25% of a shark's body mass is liver, which is also shear volume. Then again, 33% > 25%, add to the fact that the Livyatan is already smaller than the Megalodon.
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Post by theropod on Dec 1, 2015 16:00:25 GMT 5
It actually isn't. Most adult megalodons are smaller than the Livyatan holotype, irrespective of the estimate you use. It's close near the lower end though.
L. melvillei also has radically different cranial anatomy from P.macrocephalus, including a more brevirostrine, broader skull, and thus a proportionately smaller spermaceti organ. Not to mention the spermaceti chamber plays a key role for ramming behaviour in extant sperm whales.
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Post by Grey on Dec 1, 2015 16:12:09 GMT 5
Theropod you're again comparing oranges with apples while comparing the estimated length of Livyatan with the deduced mean size from megalodon shed teeth.
Livyatan holotype could very well correspond to what is a large adult in megalodon.
Or even if it was larger on average does not mean it was larger in full potential size.
I've once (3 months ago) asked C. Pimiento about comparing megalodon with Livyatan. She said "megalodon reached 18 m, L. melvillei 13.5-17.5 m, so as far as we know megalodon grew (slightly) larger".
This comes from the researcher who actually made the work you keep using.
The actual describers of Livyatan C. de Muizon and O. Lambert were totally reluctant to say Livyatan was larger than megalodon despite their enthusiasm with their specimen.
Overall they're in the same league anyway but the present data says the shark can be slightly larger.
I keep searching about the teeth in private collections for Livyatan, 5 are in Japan, the others in Europe.
Finding a significantly larger tooth would be more indicative of the whale being larger than the classic assumption holotype=medium-sized specimen.
As long as the possibility to find a larger than 18 m megalodon exists just like the possibility to find a larger than 13.5-17.5 m Livyatan, I strongly disagree with this assumption.
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