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Post by Grey on Dec 22, 2017 6:23:04 GMT 5
I don't doubt there is very good material right there, but as you said everything is blurry at this point. I even understood that he was not the discoverer of the material...
But yes this looks like a genuine meg centrum. I don't buy the measurements yet, especially I'm not sure it is not slightly eroded and incomplete.
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Post by elosha11 on Dec 22, 2017 10:32:17 GMT 5
Really, you heard he wasn't the discoverer of the skeleton? That's something I never heard before in all my communications with him.
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Post by Grey on Dec 22, 2017 10:43:14 GMT 5
I've had some discussions. That was rather confusing but enough for that I don't give him too much credential. I'm currently way more interested in the chubutensis jaw description.
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Post by Grey on Dec 22, 2017 11:46:16 GMT 5
I've explained why using vertebral diameter in the case of megalodon is problematic to estimate TL.
However, it is usually acknowledged that vertebral diameter is directly related to the body mass of a vertebrate.
Despite the potential differences, vertebra in C. carcharias and O. megalodon share some similarities.
Here I post some potential body mass estimates for the Denmark large 230 mm vertebra extrapolated from vertebral measurements with known body mass from Henry Mollet data set, irrespective of any TL estimation.
As ever, this is only indicative as the vertebra was not necessarily the largest and assuming meg had a similar bulk than the GWS, but at least this are figures directly extrapolated from vertebral measurements and this gives a pretty reasonable idea of the body mass that was reached by the Denmark individual when it was living.
Based on 3 GWS specimens, the 230 mm centra could correspond to a shark of 39 607 kg; 45 111 kg; 28 849 kg (without liver).
Irrespective of the TL, the centra at least strongly confirms that if O. megalodon was GWS-shaped, body mass comparable to that of a large modern male sperm whale are realistic.
People need to remember, no need to focuse on maximum figures, this superpredatory shark really had almost unimaginable proportions.
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Post by elosha11 on Dec 22, 2017 12:13:41 GMT 5
Which Mollet specimens are you using? I assume the MALTA and KANGA giants, or something else? What would your calculations be for 260 mm diameter for centra for the alleged Peruvian specimen?
BTW, I believe your counterpart poster in AnimaliaForum stated (I think on AnimaliaForum, not here) that the Peruvian specimen had only around 190 centra. If Klaus is being accurate, however, he told me that that specimen's centra count exceeded 200. Obviously, we don't know if Klaus is being accurate or not, but I do have to say that his figures match up pretty well with what would be expected of a complete Meg skeleton ...
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Post by Grey on Dec 22, 2017 12:32:31 GMT 5
Which Mollet specimens are you using? I assume the MALTA and KANGA giants, or something else? What would your calculations be for 260 mm diameter for centra for the alleged Peruvian specimen? BTW, I believe your counterpart poster in AnimaliaForum stated (I think on AnimaliaForum, not here) that the Peruvian specimen had only around 190 centra. If Klaus is being accurate, however, he told me that that specimen's centra count exceeded 200. Obviously, we don't know if Klaus is being accurate or not, but I do have to say that his figures match up pretty well with what would be expected of a complete Meg skeleton ... I used three specimens on Mollet page where vertebral diameter is available, not KANGA or MALTA, no vertebral measurements are available for those. Accordingly, those are pretty hefty specimens but nonetheless the results are legitimate. I want to avoid estimates based on unpublished, unverifiable, problematic material. But respectively for a 260 mm vertebra 57 214 kg; 65 743 kg; 41 674 kg (w/o liver). Nothing extraordinary, that's simple cubic scaling, but at least based on a material that is directly correlated to body mass in vertebrates, not derived from TL/body mass data. My point is that, irrespective of the TL estimations, the available vertebral centra strongly suggest a potential range of 30-45 tonnes for the Denmark specimen, even tough two of those GWS specimens as basis were pretty heavy, the lower estimate is without liver. This results in a reasonable range. One potential issue regarding meg body mass is the liver. It is difficult to extrapolate if the liver would be just as heavy as in GWS. And if it wasn't, if other organic parts grew actually bigger on the contrary. The 230 mm vertebra simply "confirms" at least one individual weighed in the area of the 30-45 tonnes. Hönninger reported 194 vertebra originally but there were some missing. Anyway, 194 is extremely close to Gottfried prediction and still higher than in GWS. I think Gottfried predictions are fairly realistic and one of the best part of his 1996 work. Also, I should note the high vertebral count expected in O. megalodon doesn't seem to correspond to an extremely stocky shark, at least not as much as what is implied by the more modest TL figures proposed by my "counterpart". Although more needs to be digged there. Megalodon had probably a larger vertebral count than in the GWS and for the same anterior tooth size, had a larger dentition. The increase in size/count of those parameters suggest the species had, overall, a generic lamniform body shape. |
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Post by prehistorican on Dec 22, 2017 21:43:01 GMT 5
“I understood this idea. But this Otodus megalodon centra not only much longer than C. carcharias/C. hubbelli centra, but also much deeper and has differing proportions. It's almost certainly occurs from a different position. Gottfried et al. as well as Bendix-Almgreen & Svend write about similar morphology of O. megalodon vertebrae and Carcharodon carcharias vertebrae. If Gottfried diameter-based metod gives reliable estimate for IRSNB 3121, I think that we must use it. ”
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Post by creature386 on Dec 23, 2017 0:16:03 GMT 5
"Single isolated tooth? Any estimates that based on such fragmentary material can not be called "conservative". It is very similar to undescribed 40-45 cm isolated pliosaur tooth or TSMHN 1125 & NHMM 603092 Mosasaurus hoffmanni specimens for me."
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Post by Grey on Dec 23, 2017 23:38:49 GMT 5
"Single isolated tooth? Any estimates that based on such fragmentary material can not be called "conservative". It is very similar to undescribed 40-45 cm isolated pliosaur tooth or TSMHN 1125 & NHMM 603092 Mosasaurus hoffmanni specimens for me." Gottfried and Shimada methods are described by their authors as conservative, for several reasons. Compared to whole dentition based method, the conservative results of those methods are even more obvious. I explained why, the differences in proportions in the dentitions between the two genuses. |
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Post by Grey on Dec 23, 2017 23:42:51 GMT 5
“I understood this idea. But this Otodus megalodon centra not only much longer than C. carcharias/C. hubbelli centra, but also much deeper and has differing proportions. It's almost certainly occurs from a different position. Gottfried et al. as well as Bendix-Almgreen & Svend write about similar morphology of O. megalodon vertebrae and Carcharodon carcharias vertebrae. If Gottfried diameter-based metod gives reliable estimate for IRSNB 3121, I think that we must use it. ” I know Gottfried and the Danish paper hint at the similarities between meg and GWS centra. This doesn't mean there aren't specific differences at a certain extend. So far I've not seen any GWS centra looking like Hubbell centra. |
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Post by Infinity Blade on Dec 25, 2017 0:19:08 GMT 5
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Post by Grey on Dec 25, 2017 9:36:21 GMT 5
Yup, this highlights why using isolated centra is impossible to use properly. At the very best, it provides a minimum estimation of the size. So far, I've not seen any modern great white and lamniform centra looking like this particular centra. Note also that Gottfried 1996 suggests the Belgian column had anterior centra probably missing as well. Nope, I can't say too much for now, but looking at the additional data, it appears the variation resulting from using an isolated tooth compared with a whole dentition isn't great, as long as we use material at a similar ontogenic stage. There is another dentition from Chile comparable or larger than the Yorktown dentition. The goal is to get a valuable data for various whole dentitions, then apply an isolated tooth to a known position. Mike Siversson uses that method and considers it the most reliable available so far. |
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Post by Grey on Dec 30, 2017 22:44:19 GMT 5
Another comparison.
The Carcharodon hubbelli specimen is estimated at 4.89 m TL based on available vertebral width and 5.07 m TL based on average crown height.
The summed upper crown width on one side is 313 mm.
The summed upper crown width of the Yorktown Otodus megalodon dentition is 1147 mm.
This O. megalodon dentition is approximatively 3.6 times larger than the C. hubbelli dentition.
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Post by elosha11 on Dec 31, 2017 22:18:30 GMT 5
^ Which yields a length range of between 17.6 to 18.25 meters for the Yorktown Megalodon, right along the lines of the research you and your colleagues have published so far. Grey, it might be good if any follow up papers on the Yorktown Meg mentions this point with C. hubbelli, to further support the predictive value of your methodology.
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Post by Grey on Apr 7, 2018 3:03:34 GMT 5
Some news.
Got new updated results, excluding the outliers in the study, establishing the Aurora adult at 16.68 m based on upper dentition and the Bone Valley juvenile at 11.44 m.
The Chilean dentition is gonna be measured soon. The results will be presented at a meeting in september.
Preliminary results still suggest some of the largest isolated teeth would hint at dentitions corresponding to 20 m plus sharks.
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