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Post by Grey on Mar 22, 2014 12:11:23 GMT 5
I've established contact with a French collector highly knowledgeable about Megs teeth. Here are three of his specimens, all from South Carolina. They range in size (slant) at 16 cm, 17 cm and 18 cm. The 17 cm specimen is 13.2 cm wide. The 18 cm specimen is 13.6 cm wide.  The largest one :  That lateral is humongous, very large and 17 cm in slant :   I'd guess the width is approaching 15 cm...? That one is 17.1 cm in slant :  16.9 cm :  17.9 cm :  At last, he indicated me that famous one is 18.54 cm in slant. Its width probably exceeds 15 cm IMO :  |
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Post by theropod on Mar 22, 2014 15:55:45 GMT 5
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Post by theropod on Mar 22, 2014 21:15:13 GMT 5
Both seem to resemble 2nd or 3rd laterals the most imo
And they are the most similar in terms of slant-lenght/width ratio too.
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Post by Grey on Mar 22, 2014 21:30:09 GMT 5
My opinion too. I'll try to get a rough estimate of toothrow length and TL based on these teeth. But I really guess these ones effectively likely come from absolutely colossal sharks.
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Post by Grey on Mar 22, 2014 22:29:02 GMT 5
I get something roughly in the range of 18 m to a bit more than 20 m TL for both teeth, depending the position, with a mean a bit more than 19 m.
I wonder if the estimated ~14.9 cm lateral might be even a L4.
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Post by theropod on Mar 22, 2014 23:08:02 GMT 5
Assuming an L2 position, Lowry et al. gives us at most 18.1 and 19.5m for the larger of the two, based on both tooth sets. Using 10-11m to scale from CH-31 you get 16.7m and 18.4m.
L2 is perfectly fine. Basically, you don’t get any closer to the slant/width ratio of this piece with all but posteriors, and this tooth obviously isn’t a posterior since those are so wide simply because their crowns are atrophied.
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Post by Grey on Mar 22, 2014 23:19:22 GMT 5
I've not used Lowry in the absence of the appropriate percentage, I'm awaiting a response for this. What is CH-31 ? I've not used a 10 m figure for Hubbell's set but the estimate from Siversson of 11-12 m.
L2 is almost equilateral with very straight crown sides, the huge lateral has a bended crown, I don't think it is certainly a L2. More likely a L3 with a slightly more bended crown. In terms of shape, I don't think L4 is a posterior tooth but the last lateral. The shape of the ~14.9 cm tooth looks like a L4 which has a clearly bended crown and a slant height slightly larger than its width.
Not saying it's a L4 but that's not impossible. The only problem to me is the size, this potentially result in a freaking TL.
Edit : I can confirm that L4 is a lateral position, not posterior.
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Post by theropod on Mar 22, 2014 23:24:26 GMT 5
All positions behind the third (=anterior) tooth can be called laterals. My point was that L2 is closer to this one in terms of proportions than L3 or L4.
L3 and L4 aren’t more assymetrical than L2, and this one’s slants are almost the same lenght.
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Post by Grey on Mar 22, 2014 23:32:02 GMT 5
Actually it seems the huge lateral is somewhat fitting perfectly for L4.   Yes, that potentially comes from an individual in the upper bound of the species, perhaps a freak. (Don't take attention to the small U3, that's from when they thought megalodon had the same bended U3 than in the white shark) |
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Post by Grey on Mar 22, 2014 23:35:03 GMT 5
L2 is almost equilateral. The 18.54 cm slant specimen is quite possibly a L2 or L1 though.
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Post by theropod on Mar 22, 2014 23:36:46 GMT 5
Actually it seems the huge lateral is somewhat fitting perfectly for L4. Yes, that potentially comes from an individual in the upper bound of the species, perhaps a freak. (Don't take attention to the small U3, that's from when they thought megalodon had the same bended U3 than in the white shark) Do you trust that diagram, despite it obviously having been made without much actual knowledge of meg dentitions (tooth count far too high, dental proportions incorrect…)? That is, quite literally, a fantasy line-drawing. Have a look at this, at least it is based on an actual fossil assemblage:  Compare the forth, fifth and sixth upper teeth. I don’t see a notable difference in terms of crown asymetry, they all show a subtle mesial inclination (it is stronger in this specimen). L2 is most similar in terms of its lenght/width ratio, and given its size it is by default our most likely candidate. EDIT: Oh, that picture is CH-31, Hubbell’s tooth set. No idea whether that catalogue number is in some way official, but it’s the one used by boneclones, where we also have our measurements from. |
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Post by Grey on Mar 22, 2014 23:41:28 GMT 5
The only problem with that diagram is that it has the Gottfried-Purdy-Espinosa U3 bended tooth, the assignement of teeth (and L4) is the same as now.  This does not change anything to the assignement. Posteriors teeth are the last 4 teeth in the upper jaws. L4 in either model is a lateral. The ~14.9 cm wide tooth is perhaps a L4, or L3, or L1, but not a L2 IMO because of the bended crown. |
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Post by theropod on Mar 22, 2014 23:44:37 GMT 5
it has two teeth too many...
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Post by Grey on Mar 22, 2014 23:47:18 GMT 5
Well done, but L4 is still a lateral, not a posterior either way.
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Post by theropod on Mar 22, 2014 23:49:18 GMT 5
My intention was not to discuss sematics, and I never implied L4 was a posterior.
Usually it’s the last 2-4 teeth that are labeled posteriors.
I use the Pimiento et al. labeling, just anteriors (A or a) and laterals (L or l). Laterals can be further specified to be anterior, mid or posterior ones if that is necessary.
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