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Post by creature386 on Jul 12, 2013 20:16:11 GMT 5
It would be even worse if it gets too heavily damaged (it already got some damage).
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Post by Grey on Jul 13, 2013 0:18:35 GMT 5
Information by Bretton Kent regarding anatomical specificties in meg, best method of estimate question and mouth shape and bite force in two subsequent mails.   |
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Post by Grey on Jul 13, 2013 11:13:07 GMT 5
Comment of Brett Kent about the problem of meg jaws reconstructions based on great white and mention if him possessing a 13.5 cm wide upper lateral (allowing a justifiable estimate based of Jeremiah's method).  |
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Post by Grey on Jul 13, 2013 17:09:02 GMT 5
 From the fossilguy. The upper anterior is reported at 15.2 cm, though not missing parts of the roots and the tip. However, it quite exceeds 5 inches in width (12.7 cm) and perhaps originally was 5.5 inches wide (13.97 cm). By tooth height, it is already likely representing a large individual, as we've seen since a while (I will avoid to make Gottfried estimate given the uncertainty in that it counts slant height or truly vertical height) . If tooth width however is the best alternative at estimate total approx. size, we get a shark exceeding 17.4 m and perhaps approaching 19.1 m TL. |
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Post by Grey on Jul 15, 2013 16:59:24 GMT 5
  From Chile, 16.7 cm (in slant ?), 13.49 cm wide.   From Baja, Mexico, 15 cm in slant, 13.51 cm wide. Obviously not an upper anterior. By width method, the respective owners of these teeth were 18-18.5 m TL.  Lower anterior from Morgan River. (Note : assuming the crown is 110-120 cm and depending the position of the lower, I get a size range of 15-21 m by Shimada's method)  From Morgan River too, 12.7 cm wide. |
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Post by theropod on Jul 15, 2013 18:12:11 GMT 5
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Post by Grey on Jul 15, 2013 19:37:54 GMT 5
Well done for finding the original page !
Shimada's method is using the labial side of the crown, I've guessed using the pic of the lower anterior. The crown seems to be 12.5 cm long in slant, so in labial view I've guessed 11-12 cm. Because of the perspective I don't think this verifiable sadly. But since lower anterior are smaller than upper, the owner may have been substantial in body size.
Good news, Brett Kent just found who currently owns the gigantic Chilean meg he referred and is going to ask permission to get a photo.
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Post by theropod on Jul 15, 2013 20:59:59 GMT 5
That's indeed good news.
Why do they always figure the lingual side of the teeth? On that specimen we cannot verify the labial perpenticular crown height. But we could have a try finding out ratios on similar teeth.
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Post by theropod on Jul 15, 2013 21:02:10 GMT 5
what do you get for this tooth using Shimada? en.wikipedia.org/wiki/File:Megalodon_tooth_ruler.jpgIt is 9,4cm in crown midline lenght (to the apex of the root), 12,45cm in maximum lenght (to the proximalmost ptrotrusion of the crown) measured in the same plane and 14,1 in "Crown slant lenght" |
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Post by Grey on Jul 15, 2013 21:49:36 GMT 5
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Post by elosha11 on Jul 15, 2013 22:20:08 GMT 5
Grey - is that Chilean tooth Kent referred to the one described as barely fitting into a cigar box and thought to perhaps exceed 20 cms in slant height?
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Post by Grey on Jul 15, 2013 22:59:05 GMT 5
Yes that one, he just said he coincidentally found who was the owner and is trying to get the permission to have a photography of it.
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Post by theropod on Jul 16, 2013 1:01:09 GMT 5
Are we going to see that photograph? Because I'm really eager to see it.
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Post by Grey on Jul 16, 2013 10:40:02 GMT 5
Just wait ! He said me this that he was going to ask permission only yesterday, if he successes he will send me a pic (he sen me the chapter and his modified meg reconstruction). Depending of the owner of the tooth, I'll show it directly on the board or through PM.
Brett also agrees that there is an error in the calculation of Renz in his book, a 12 cm wide UA indicates a 54 feet meg (16.4 m) not a 51 footer (15.5) m.
He also agrees that the second upper lateral is the widest tooth in the dentition. So if you found a particularly wide upper lateral, most likely it is the second upper lateral. If you mistakenly assume this a L1 or L3, you risk to get an overestimate of the total length.
It seems that the L2 is the widest of the teeth, but since it is more difficult to identify the position of an upper lateral, that is the reason why the first UA is used for predict the size. You can note that Jeremiah, when using a great white as example in Renz, uses the UA. That's also because in the great white, unlike meg, the first UA is the widest tooth in the dentition.
Depending the assignment, you can have under and overestimates. If I found a very wide UA, I will assume it is the first, a very wide UL, I will assume it is the second.
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Post by Grey on Jul 23, 2013 18:09:21 GMT 5
As seen earlier, Bretton Kent acknowledges that, in the absence of hard data about the jaw perimeter, the tooth width method is the best available method for predict the size of megalodon. Sadly, it also shows the inherent problems to isometry. Brett Kent has used the Jeremiah's formula within a sample of great whites known by they body length and tooth width.  It appears that the value by Jeremiah is the mean line between the various results. As you see however, the disparity increses with growing, a tooth 4 cm wide can belong equally to a shark about 4.7 m and 6 m respectively, with ~5.4 m being the mean size predicted by Jeremiah's method. A potential range of So when reaching megalodon's proportions, the potential range could exceed 3 m. However, Gordon Hubbell that while it is difficult to estimate size from teeth in sharks, that's especially the case of the white shark. I know that Mike Siversson performed this too based on others species such as Isurus and Lamna and came to conclusives results, sadly unpublished. As meg is not a direct relative of the white shark, if the method is more efficient (with less disparity relative to the size) based on others sharks such as Isurus, possibly this can bring more credential to that method. This remains the best method though since it represents a mean value, similar to Shimada's calculations based on crown height. I know for discussing with Dana Ehret on Facebook that he favors too Jeremiah's method : I also prefer Cliff Jeremiah's predictions to Shimada's. While I do think that white sharks can make good models for Megalodon, we do need to remember that they are not as closely related as once thought.So, despite the potential error, since Jeremiah's method represents a simple mean value and that tooth width is seemingly better (or least worst) than tooth height of crown height, I agree with a TL approaching 20 m based on the largest teeth. |
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