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Post by Grey on Mar 22, 2014 23:53:06 GMT 5
That's what I understood in the first feedback.
Anyway, my opinion is that this huge tooth looks like a L4, but an assignement to L3 or L1 is also possible to me. L2 is not impossible but all the dentitions show L2 with the most equilateral proportions, with no bended crown, so I doubt it's a L2. But it's a lateral coming from a very large shark, in the same ballpark IMO than the largest specimen owned by Gordon Hubbell.
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Post by theropod on Mar 22, 2014 23:56:39 GMT 5
That is possible. Which dentitions are you talking about?
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Post by Grey on Mar 23, 2014 0:00:15 GMT 5
By the dentitions I mean I refer to the various models and diagrams. Shape can slighty change from one to another, but overall these indicate me this lateral tooth has perhaps better assignement than L2.
The other at 18.54 cm in slant on the other hand almost perfectly fits the L2 position.
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Post by theropod on Mar 23, 2014 0:13:09 GMT 5
Actual dentitions however do not reflect this.  Two line drawings, one terribly outdated, the other very rough, don’t seem solid proof to me. I don’t see such major differences between the two big teeth either. The wider one has a more pronounced concavity in its carina, which is because it’s tip has a more robust, wider shape (which, in turn, is why it is shorter, but nevertheless it is wider, i.e. it is very compact). But the anterior four laterals are all not that strongly inclined to one side. The crowns are bent very slightly and have more or less curved carinae, but as you see that’s common to all of them. L2 is simply the most robust and the biggest one, and this specimen? meets both criteria perfectly. Do you have details on this dentition you posted earlier?  |
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Post by Grey on Mar 23, 2014 0:49:29 GMT 5
This dentition is the one from Hubbell I think but I'll check this. Edit : I think it's Uyeno.
And L2 does not fit perfectly, as it is not bended, whereas the tooth is clearly bended. Other lateral are more bended than L2 so are more likely.
The two big teeth show a different crown structure. It is not impossible both are L2 but most of the diagrams indicate the ~14.9 cm is most likely not a L2. The shape even fits more a L4.
And the purpose of these drawings are especially to assign a position for each tooth. I once asked to Balk to indicate me a position for a tooth and she sent me the diagram for Pimiento et al. saying this might help. The one by Espinosa appears outdated on some points but not on the assignements of the lateral teeth. Everything has not to be rejected.
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Post by theropod on Mar 23, 2014 2:38:44 GMT 5
How do you know it is not outdated on the assignments of the lateral teeth? Especially the shape of the first 3 laterals seems off, more alike to certain anteriors in the symmetry of the crowns and the convex edges. Certainly not a surprise in a diagram that also reconstructed the dentition with too many teeth and reconstructed others the wrong way.
Again, what we need is a proper guide to identifying teeth. Especially since we lack one, we should be very cautious on these matters.
DIT: I should have been more specific, a guide involving detailed diagrams and actual text, not a line drawing.
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Post by Grey on Mar 23, 2014 7:57:32 GMT 5
The assignements of the lateral do not appear outdated as it is similar to the one in Pimiento et al. The main differences with the older reconstructions are the bended third upper. I don't know why there are aditionnal posteriors in it. There are guides for identifying teeth, the diagram in Pimiento et al. is one of them. Based on the slightly bended crown, I doubt it is certainly a L2. But I'm going to investigate this. BTW theropod, have you an idea of the crown height of these two big lateral ? I know you don't rely so much on Shimada's method but it can be interesting to have a figure here too. And lateral teeth are perhaps less subject to under or overestimates than upper and posterior. On my side I'm investigating the most likely position of the big lateral. |
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Post by theropod on Mar 24, 2014 1:47:22 GMT 5
I’m busy right now, but you can measure it yourself, you have all the measurements and pictures needed. theworldofanimals.proboards.com/post/11824It’t true the (anterior) laterals are the least affected, but there is some degree of skewness with all the tooth positions. |
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Post by theropod on Mar 24, 2014 1:57:24 GMT 5
Never mind, I couldn’t resist. I measured the crown height on the 14.9cm wide specimen at 121.8mm (again, using slant lenght as a scalebar, so it’s not very precise) and on the 14.6cm wide one at 125.5mm. That gives us 16.4 and 16.9m in TL using the L2 regression (which both ought to be somewhat underestimated).
But I trust the width more since tooth height is not actually that closely linked to the mouth size to begin with, even without taxon-specific differences.
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Post by Grey on Mar 24, 2014 2:04:14 GMT 5
Well I'd got a crown height of 13.33 cm for the wider specimen but I'm really not precise at this. Anyway good job. But I'm really not convinced that the wider one comes from the L2 position. Not sure at least. theropod Well for now I have the opinion from two experienced collectors, one tends toward L3, the other L4. |
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Post by theropod on Mar 25, 2014 2:09:25 GMT 5
Who?
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Post by Grey on Mar 25, 2014 2:24:49 GMT 5
You don't know them, they are privates. I'm going to ask to scientists.
However the exact width of the tooth is more like 14.3 cm. Regardless that's still a humongous tooth for its position.
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Post by theropod on Mar 25, 2014 17:32:20 GMT 5
That depends on how you assign it. It is a huge tooth, but its position matters a lot here.
The measurement comes from the owner I presume? I´d still like to know the references, unlike he/she wants to remain anonymous for some reason.
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Post by Grey on Mar 26, 2014 1:33:48 GMT 5
Actually that tooth is a bit problematic as it is partially geriatric. For discussing with two experienced collected as well as Jim Bourdon and Bill Heim, if the original size was indeed 14.3 cm, it may have been a L3 or L4. But it could be that it was an UA3 enlarged with an original width of 12.7 cm. Regardless, that tooth represents a massive dentition from perhaps a massive or very massive meg. There is also the case of the Atacame chilean tooth. Apparently it is a L3 or L4 too and that one was not partially reconstructed. I don't remember its exact width but I think you had measured it at something above 13 cm.  If true, it indeed comes from a giant. Siversson estimates it at 18 m, but given its position that's possibly a conservative estimate. There is also the case of that massive posterior which is 9.1 cm wide, owned by a french private. I think it comes from South Carolina.  It perhaps comes from the UL7 position.  If Siversson estimate of 11 m for Hubbell's specimen is true and that the proposed assignement here is reasonnable, this posterior corresponds to a massive dentition potentially suggesting an Otodus megalodon at 20 m. Nothing certain here, I'll have more precise information or confirmation in the following days. |
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Post by Life on Mar 26, 2014 1:57:41 GMT 5
Megalodon approaching 20m in total length (TL) seems to be a realistic assessment.
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