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Post by Grey on Jun 22, 2013 23:38:40 GMT 5
That's weird, it would make Jeremiah's conservative, which I don't think can be considered as such, despit giving less large results than the direct sizing. But since it works with others lamniforms as well, it is still interesting. However, I have faith in it but not that much. My personnal opinion about meg size is the one of Brett Kent, very cautious. I believe that a maximum size of 18 m TL is possible given the uncertainities of such methods, but I'm opened to sizes approaching 20 m TL proposed by Siversson given that the root width works well with others lamniforms than the white shark. And also given these hints of this large skeleton. For personnally speaking with Klaus Hönninger, I know he thinks that regarding that unique meg skeleton specimen, an appropriate method would be 2,7 m per inch of UA tooth in slant height, but he advised me to not consider this one as valid yet. I think a maximum (at least known to date) of ~19m as stated by Siversson is most likely, based on the root width table. But apparently, it is in disagreement with what you can read in "Hunting the Hunted". I just whished that book was a bit more in-detail and not just superficial. It contains really nice photographs of bite marks tough. We have to determine which is accurate, the 1,25m/cm or 1,37m/cm root width. for the largest known teeth, that makes a difference of almost two metres. I think the 1,25m/ cm is off as the video I've just posted you can hear they quote the 4,5 feet (1,37 m) per cm figure instead. I'm opened for a 19 m TL proposed by Siversson using Jeremiah's method, but I'd prefer stay on the 18 m mark proposed by Kent awaiting more conclusive data. This is where we need the meg skeleton (I don't know the width of the teeth but Klaus talked me about 14 cm wide specimens). |
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Post by Grey on Jun 22, 2013 23:44:10 GMT 5
Theropod, if you consider Siversson and Jeremiah as plausibly valid, you have to keep in mind they, very much like Gottfried, Shimada and others, use the largest or widest teeth available. Use Jeremiah's method on that specimen however, the ruler is in inches.  Once again, I don't take all of this as facts, but possibilities... |
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Post by theropod on Jun 23, 2013 0:40:40 GMT 5
^I know, I supposed this was about the size of the largest specimens known.
Not sure about the numbers. 4,5ft sounds suspiciously rounded...
Were was the table from again, and how reliable is it (Why?/Why not?)?
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Post by Grey on Jun 23, 2013 0:47:12 GMT 5
^I know, I supposed this was about the size of the largest specimens known. Not sure about the numbers. 4,5ft sounds suspiciously rounded... Were was the table from again, and how reliable is it (Why?/Why not?)? It sounds rounded in feet, but it's 1,37 m in meters. That's what is most commonly cited and used (Siversson). The table was from the Megalodon Exhibit supervised by several specialists including Jeremiah, Hubbell, Purdy and Ehret. |
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Post by theropod on Jun 23, 2013 1:58:27 GMT 5
So which is right? Difficult to say, what do your contacts say about this?
One thing, if 1,37m is right, you are far too conservative with your size suggestion, and the produced estimates will be extremely high.
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Post by Grey on Jun 23, 2013 2:20:50 GMT 5
4,5 feet or 1,37 metre seems to be the correct one, that's what is used by Mike Siversson.
Why conservative ? I don't think so, the results are high using the widest teeth in existence. I wouldn't call a 18-19 m TL meg conservative !
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Post by theropod on Jun 23, 2013 2:47:09 GMT 5
Plenty of the teeth you posted in this thread would yield such sizes or even higher ones, and that is just the root width, not the (intentionally highly) liberal direct scaling. Were did siverson give the figures btw?
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Post by Grey on Jun 23, 2013 3:11:19 GMT 5
Plenty of the teeth you posted in this thread would yield such sizes or even higher ones, and that is just the root width, not the (intentionally highly) liberal direct scaling. Were did siverson give the figures btw? Siversson clearly refers, like many sharks specialists, to the Hubbell's tooth, which seems to be best known specimen among paleontologists specialized in sharks. The tooth is 13,7 cm wide. This results in a shark about 18,8 m, approaching 19 m. I know he uses it through my dicussions with him. As always with megalodon teeth, scientists only use what they have on their hand or know. Anyway I prefer the root width than the direct sizing, though the first direct sizing calculation based on a 6,4 m white shark, gives results looking alike to what Klaus reported me a number of time about meg size. But this is not published, and though possible, these results are not yet conclusive, that's why I personnally prefer stay at the 18 m TL commonly proposed by several authors. I think we'll know more sooner or later with that skeleton in Ica... And I have to relativise these numbers, as 18 m as TL is a size almost unbelievable for a predatory shark or even an active marine carnivore, given the physical constraints at this scale. For now I'm comfortable with 18 m, with non-conclusives possibilities toward sizes up to 20 m or a bit more (like proposed Kent 2 years earlier). |
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Post by Grey on Jun 23, 2013 3:16:00 GMT 5
BTW, the direct sizing gives the sizes estimates used by Wroe et al. in 2008. That indicates that this estimate is not ruled out, even though I can't have very much faith in it...without rejecting it either...
I know also a comment by Pimiento in an article where she states these sharks grew up to 60-70 feet, even though the largest adult found in the nursery was estimated at 16,8 m, based on Shimada.
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Post by theropod on Jun 23, 2013 13:54:15 GMT 5
I tought the 20,3m stated by Gottfried and later used by Wroe were just a speculative maximum?
When direct sizing, I would have far more fait in the average of the 10 sharks reported by Gottfried than in those freak specimens.
Then, the whole table appears to be wrong. The total lenght/root width ratio is mostly between 125 and 128, with one outlier (the smallest specimen) at 130, and the largest at 125. This table also looks like it is for C. carcharias. If those are real widths, not madeup wones, 137 would imply proportionally smaller teeth.
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Post by creature386 on Jun 23, 2013 13:55:42 GMT 5
I tought the 20,3m stated by Gottfried and later used by Wroe were just a speculative maximum? It is the most liberal estimate for the specimen with the 16,8 cm tooth. |
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Post by Grey on Jun 23, 2013 14:02:04 GMT 5
I tought the 20,3m stated by Gottfried and later used by Wroe were just a speculative maximum? When direct sizing, I would have far more fait in the average of the 10 sharks reported by Gottfried than in those freak specimens. Then, the whole table appears to be wrong. The total lenght/root width ratio is mostly between 125 and 128, with one outlier (the smallest specimen) at 130, and the largest at 125. This table also looks like it is for C. carcharias. If those are real widths, not madeup wones, 137 would imply proportionally smaller teeth. Check the results on the direct sizing based on 7,1 m great white : 20,3 m. The purpose justly is to determine the hypothetical max size of meg based on max size of the great white with a 6,6 inches tooth specimen. I don't know about the tooth width, but I know Jeremiah used it on a 17 feet white shark. This is not surprising though that it is not always corresponding with the ratio in the white shark, as white sharks teeth seem to always vary in size and width from one individual to another (see Hubbell's video). But it actually works with others lamniforms than the white shark ( Lamna nasus...), since the white shark is perhaps not an adequate mirror for meg, it potentially has credit. |
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Post by theropod on Jun 23, 2013 14:08:27 GMT 5
Oh, that was basing on the direct sizing of the cuban female. Well, it is a very oddly proportioned animal obviously, greatly differening from the normal ratio. The specimensa are stated as doubtful and therefore excluded from the regression equation. The average of 5,5m/5,92cm is undoubtedly more reliable.
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Post by theropod on Jun 23, 2013 14:12:51 GMT 5
The more important it gets to see the method published and documented properly.
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Post by theropod on Jun 23, 2013 14:13:14 GMT 5
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