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Post by elosha11 on Feb 20, 2014 23:11:38 GMT 5
A bunch of you are becoming quite the experts, (or at least educated guessers),  on the jawline position of various Meg teeth. It's obviously not set in stone, as we and others debate those points. Grey I don't suppose Pimiento has opined about the position of the newly discovered tooth? On another matter, in Gottfried's original work, didn't he include a picture of a more or less complete vertebral centra of a 9-10 meter Meg? I can't remember if it included associated teeth, but I remember seeing the picture posted in carnivora at one time. In fact I think Creature386 may have posted it there. Now I believe it may be problematic whether the vertebral centra were arranged properly, and Grey has told me the skeleton is now, regrettably archived in a museum, I believe in Europe. If anyone could find the appropriate image from the Gottfried image and post it, that would be great and may inform our discussion further. |
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Post by Grey on Feb 20, 2014 23:29:27 GMT 5
The teeth were not associated with the vertebral column.
I'm not sure how large was the column itself. Gottfried did not say anything about, he just proposed a size estimate of the shark. I can't remember if my contact biologist said me or not if the column was 9 m itself. But for sure it wasn't assembled correctly.
Still that's really stupid such a piece to be archived...
Pimiento has not yet stated anything about the tooth, picture sent by her colleague, so she did not handle it.
But at least a position statement would be useful.
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Post by creature386 on Feb 21, 2014 1:17:57 GMT 5
Is complete vertebral centra of a 9-10 meter Meg? I can't remember if it included associated teeth, but I remember seeing the picture posted in carnivora at one time. In fact I think Creature386 may have posted it there. I don't think I did so, I know that I have talked about it, but I can't remember having posted a picture. |
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Post by theropod on Feb 21, 2014 2:25:10 GMT 5
This one?  I think one of our foremost priorities should be to leanr to rigorously assign meg teeth to positions. It seems this is challenging even to experts, but without some degree of confidence in their assignments, I’m sure they would not publish them (although it seems an exact identification may not be possible with isolated teeth). |
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Post by creature386 on Feb 21, 2014 2:28:15 GMT 5
Yes, this one is meant. It is the one where Grey said it's a compromise of multiple specimens. |
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Post by Grey on Feb 21, 2014 2:40:44 GMT 5
That's the posterior which are difficult to assign, others are more remarkable. The tooth I've posted is obviously not an upper anterior, nor an upper posterior, that's a lateral now which one exactly is a matter of discussion but looking at the dentition, I'm quite believing a L4 or L5. L4 is actually a lateral anterior and L5 a lateral posterior.  |
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Post by theropod on Feb 21, 2014 18:40:14 GMT 5
I think that diagram is not adequate for identifying teeth, its too rough. Just a schematic representation to demonstrate the terms used for the teeth, but not detailed enough to identify them with it.
The differences are often quite subtle.
Nope, the problem is not the rough assignment of whether it´s anterior, lateral or posterior, but among laterals L1 through three are not the same as L6.
Are you sure this one is so huge? Was there a width measurement?
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Post by Grey on Feb 21, 2014 21:58:44 GMT 5
Hmm I'm not agreed, the diagram is precise and clearly indicates the differences of the teeth. That's the tooth in the picture that needs to be examined properly, which is of course impossible by our own means and even for experienced eyes the picture is certainly not enough.
There was no measurements, I just have the impress that this a Lateral, with a curved crown which probably excludes the three first L IMO. But I don't think we'll get something conclusive there anyway. My feeling by viewing that picture just says me that tooth comes perhaps from a massive dentition.
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Post by theropod on Feb 22, 2014 0:56:42 GMT 5
If I match the hand in the picture to mine, I get slightly over 10cm (and I’ve got a big hand).
If that’s a L4, that would suggest ~14.5m with 15% spacing. If it’s an L5, it would suggest ~17.2.
Both base on Hubbell’s tooth set, I’ll try the bigger Japanese dentition later.
The former is a fairly typical size, the latter is big but not exceptionally so. It doesn’t seem that humungous.
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Post by creature386 on Feb 22, 2014 1:37:10 GMT 5
You said two times L4, when did you mean L4 and when L5?
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Post by theropod on Feb 22, 2014 2:08:53 GMT 5
Sorry, Typing error.
The Saitama dentition would suggest 15.2 and 16.1m respectively. The disparity between the two teeth is less marked, but the resulting figures center at around the same figure.
All of course assuming an L4 or L5 position, which I’m not convinced of, but is certainly possible (as any thing between L2 and L5 imo, but I tend towards L4 based on the proportions).
But that tooth definitely isn’t more posterior than L5, it’s far too elongate for that. Thus the individual was at best a little over 17m.
It’s a typical, or perhaps a large adult, but not exceptionally so.
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Post by Grey on Feb 22, 2014 3:18:20 GMT 5
Theropod can you recall me the size you've got with Hubbell's tooth which is the largest (widest) that I know of ?
I was more interested to use Shimada's for the tooth in the picture but without knowing the CH it's useless. Though the apparent size of the crown lets me believe of a great size. Whatever, only examining it would make this possible.
Balk again said me that none of the sizes estimates she gave until now is confident, she'll let me know when more substantial data will come.
Beside this, are we sure that in the graph the peak point reached was ~70 tonnes and the lowest ~100 kg ?
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Post by theropod on Feb 22, 2014 16:44:22 GMT 5
Here?Why are you more interested in Shimada’s method for the specimen? This is what we both agreed was likely the best available method for megalodon teeth (especially if only their width is preserved anyway). I don’t think guesses on its size are of great value. Seeing as how the above method is certainly not conservative but does not give results higher than 17.2m, I would treat that as the upper bound. The specimen’s width is what is known, and it is more relevant anyway than the height. I presume bigger and/or smaller specimens may still get added anyway, although I think the whole scope is a reasonable approximation to the size range of C. megalodon. Excluding the outliers, the smallest specimen by my measurements was 92kg (likely a neonate or embryonic individual), and the largest 75t (likely a big female), but obviously those measurements are rough and not very reliable. An interesting observation: The average of just the upper lenghts, based on those data, is 14.56m. Another reason why C. megalodon’s average adult size was likely below 15m (unless many of the largest specimens in the samples were subadult). I’m looking forward to checking that with the final data as soon as they are published.
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Post by Grey on Feb 22, 2014 21:35:56 GMT 5
I'm more insterested in Shimada here because it's the only available using the tooth of any position. But other than by guess I don't know how can we know the width of that tooth. I tend to prefer the jaws perimeter method but as we've seen earlier if I remember correctly we lacked additionnal some details (the exact spacing between the teeth). At last, both methods are based on white sharks biometry with the potential issues that are included, which means that jaws perimeter is potentially better but not by a huge margin.
If you become paleontologist you should make your own method like Shimada's but based on the jaws perimeter from any tooth, that would be the best alternative at estimating Megalodon size, if only the skeleton in Peru is not published before you become graduate ^^
But somehow, it seems that Shimada's, despite not being better than jaws perimeter, was not that criticized by the colleagues of Balk and Pimiento. I'd prefer to wait for any comment when the publication will be released.
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Post by theropod on Feb 22, 2014 22:03:40 GMT 5
My estimate was assuming a liberal spacing, and it does not give you humungously large results (in C. megalodon-terms of course). You can use the toothrow lenght with every position as well, it’s fairly easy to do even with what we have right now (and a set of formulas similar to Shimada’s would not be difficult to make, it simply includes the additional step of extrapolating the total toothrow lenght for a given measurement of a tooth position, based on the two megalodon dentitions).
An even better method can be derived as soon as the peruvian discoveries are described, then we can evaluate C. megalodon’s actual body proportions.
Using toothrow lenght is already superior to the other methods because it allows us to account for all the known differences between Carcharocles and Carcharodon, while other methods, like Gottfried et al., Shimada and even rooth width do not. Nothing so far has given us reason to assume that C. megalodon had drastically different toothrow to body proportions.
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on the jawline position of various Meg teeth. It's obviously not set in stone, as we and others debate those points. Grey I don't suppose Pimiento has opined about the position of the newly discovered tooth?
