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Post by theropod on Oct 5, 2019 18:24:03 GMT 5
I don’t remember the "2013 8 killer whales vs Livyatan" incident. You must forgive me, it must be my age. At any rate, while the rest here were busy being outraged at Shimada (2019) for giving such unrealistically low estimates based on an old and questionable method, I found something interesting: FMNH PF 11306 (Figure 1(a)) is in fact described as the largest tooth of O. megalodon in museum collections by Applegate and Espinosa-Arrubarrena (1996 Applegate SP, Espinosa-Arrubarrena L. 1996. The fossil history of Carcharodon and its possible ancestor, Cretolamna: a study in tooth identification. In: Klimley AP, Ainley DG, editors. Great white sharks: the biology of Carcharodon carcharias. San Diego: Academic Press; p. 19–36.[Crossref] , [Google Scholar], fig. 11a; erroneously referred to as ‘PF 1168’; also by Reolid and Molina 2015 Reolid M, Molina JM. 2015. Record of Carcharocles megalodon in the eastern Guadalquivir Basin (Upper Miocene, South Spain). Estudios Geol. 71(2):e032. doi:10.3989/egeol.41828.342.[Crossref] , [Google Scholar]). Although Applegate and Espinosa-Arrubarrena (1996 Applegate SP, Espinosa-Arrubarrena L. 1996. The fossil history of Carcharodon and its possible ancestor, Cretolamna: a study in tooth identification. In: Klimley AP, Ainley DG, editors. Great white sharks: the biology of Carcharodon carcharias. San Diego: Academic Press; p. 19–36.[Crossref] , [Google Scholar]) reported its total tooth height (TH) to be 168 mm and Shimada (2003 Shimada K. 2003 (date of imprint 2002). The relationship between the tooth size and total body length in the white shark, Carcharodon carcharias (Lamniformes: lamnidae). J Fossil Res. 35:28–33. [Google Scholar]) overestimated its CH to be 125 mm, my reexamination of FMNH PF 11306 shows that it is 162 mm in TH and 117 mm in CH, including inferred 2 mm of its chipped crown apex (erroneously reported its CH to be ‘168 mm’ by Reolid and Molina 2015 Reolid M, Molina JM. 2015. Record of Carcharocles megalodon in the eastern Guadalquivir Basin (Upper Miocene, South Spain). Estudios Geol. 71(2):e032. doi:10.3989/egeol.41828.342.[Crossref] , [Google Scholar], p. 10; vs. their p. 8). FMNH PF 11306 is indeed the tallest tooth I am aware of for O. megalodon (or any non-tetrapod fish species!) in museum collections, but intriguingly, it does not have the tallest CH. The tooth of O. megalodon with the tallest CH that I am aware of is NSM PV-19896 (Figure 1(b)), measuring 120 mm in CH even through its TH (149 mm) is smaller than FMNH PF 11306. The different CH:TH proportions between the two teeth almost certainly reflect different tooth positions. Both FMNH PF 11306 and NSM PV-19896 are tall but also broad and erect, suggesting that they are almost certainly upper anterior teeth. Shimada, K. 2019. The size of the megatooth shark, Otodus megalodon (Lamniformes: Otodontidae), revisited. Historical Biology 0 (0): 1–8. So 117 mm is the crown height of the tallest megalodon tooth known to meg researchers from any museum collection, and 120 mm is the tallest crown height known. That would imply the Yorktown dentition is 88% the known maximum size, based on properly verifiable specimens (i.e. held in public collections). Also note how the 15.3 m estimate is actually based on Gottfried et al.’s formula for overall tooth height, not crown height (I still don’t see why we should use crown height when tooth height is known, so this seems reasonable), for the re-measured tallest known tooth in public collections. So "megalodon has proportionately larger roots" isn’t an argument, even though the different proportions of different teeth in the dentition are of course fair criticism that I fully agree with. |
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Post by dinosauria101 on Oct 5, 2019 18:29:02 GMT 5
I don’t remember the "2013 8 killer whales vs Livyatan" incident. You must forgive me, it must be my age. It was the account that was posted on Carnivora's 8 killer whales vs Livyatan to show how long it takes killer whales to hurt large animals, and Taipan kept on parroting it to Life, elosha11, and Grey as proof they were wrong, so they left for WoA. Surely you can remember that? |
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Post by dinosauria101 on Oct 5, 2019 19:58:03 GMT 5
I think it's probably the underwater equivalent of the lone tiger killing the elephant theropod, 2 things -By remember, I meant remember that it happened -Interesting! That might change my view on many killer whale matchups |
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Post by Grey on Oct 5, 2019 20:06:36 GMT 5
Shimada remeasured the teeth but there are definitely a good count, if not many, larger teeth even in total height. I certainly recall crown heights between 125 and 140 mm.
The Black Hills (173 mm TH) and Hubbell's (129 mm?) teeth are definitely larger than the institution record from Shimada. This is even more the case for the highest lower anterior crown claimed in the study. That is a problem with meg fossils but it can't be ignored. Let akone some massive fragments of teeth at least comparable in size to some record-sized private teeth.
But I noticed something else interesting in the study, he uses power function scaling rather than linear function scaling. How this would work with other methods is interesting.
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Post by creature386 on Oct 5, 2019 20:36:46 GMT 5
I don’t remember the "2013 8 killer whales vs Livyatan" incident. You must forgive me, it must be my age. It was the account that was posted on Carnivora's 8 killer whales vs Livyatan to show how long it takes killer whales to hurt large animals, and Taipan kept on parroting it to Life, elosha11, and Grey as proof they were wrong, so they left for WoA. Surely you can remember that? I think it was the other way around. Grey used that account as evidence for his case. What Taipan kept repeating was an argumentative post (with no account) by LionClaws. |
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Post by theropod on Oct 5, 2019 20:51:04 GMT 5
I think it's probably the underwater equivalent of the lone tiger killing the elephant I guess that would rather be be the "lone orca kills large humpback whale"-incident Grey: Shimada tested for allometry using the power functions, but he seems to suggest to stick to the linear models. At any rate, the power curves suggest lower values as the exponents are consistently below 1. Using a power curve instead of a linear model also doesn’t have a big impact for the Mollet et al. dataset., about 2% for the Yorktown dentition. We already discussed it doesn’t have a big impact on the bite circumference method either. EDIT: Allometry would actually be borderline-significant based on Mollet et al.’s data, but not Lowry et al.’s, so it might be better. Ideal, of course, would be to combine both into one regression that would likely give a better signal, but for that I need a relatively reliable mean jaw perimeter/tooth row length ratio. |
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Post by dinosauria101 on Oct 5, 2019 21:19:28 GMT 5
It was the account that was posted on Carnivora's 8 killer whales vs Livyatan to show how long it takes killer whales to hurt large animals, and Taipan kept on parroting it to Life, elosha11, and Grey as proof they were wrong, so they left for WoA. Surely you can remember that? I think it was the other way around. Grey used that account as evidence for his case. What Taipan kept repeating was an argumentative post (with no account) by LionClaws. I believe it went BOTH ways. LionClaws did make a post comparing the analogy to an eagle against several smaller hawks, and then Taipan parroted both that post as proof Livyatan would lose and also parroted that account of the blue whale as proof that the killer whales could quickly injure Livyatan |
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Post by Grey on Oct 5, 2019 21:24:50 GMT 5
I don’t remember the "2013 8 killer whales vs Livyatan" incident. You must forgive me, it must be my age. It was the account that was posted on Carnivora's 8 killer whales vs Livyatan to show how long it takes killer whales to hurt large animals, and Taipan kept on parroting it to Life, elosha11, and Grey as proof they were wrong, so they left for WoA. Surely you can remember that? It probably took long because the blue whale was swimming fast, it is unlikely a similar-sized predatory shark would react. But it is clear that transients can at least deeply hurt gigantic prey. Would an adult meg be seen as an interesting prey is another question. Unlikely. |
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Post by Life on Oct 5, 2019 22:53:20 GMT 5
It was the account that was posted on Carnivora's 8 killer whales vs Livyatan to show how long it takes killer whales to hurt large animals, and Taipan kept on parroting it to Life, elosha11, and Grey as proof they were wrong, so they left for WoA. Surely you can remember that? It probably took long because the blue whale was swimming fast, it is unlikely a similar-sized predatory shark would react. But it is clear that transients can at least deeply hurt gigantic prey. Would an adult meg be seen as an interesting prey is another question. Unlikely. Well, killer whales cannot immobilize the Megalodon and/or kill it in a short span - assuming an adult. Given the sheer size and implied power, the Megalodon could easily endure a few bites and would have time to react to the moves of killer whales. It might kill one or two and force the pod to give up (or) simply dive deeper and escape. Great whites do not have similar luxury (if caught) because even a lone killer whale is much larger in comparison and can immobilize one without much issue. So yes! Unlikely. Not worth the risk. |
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Post by theropod on Oct 6, 2019 4:14:28 GMT 5
Shimada remeasured the teeth but there are definitely a good count, if not many, larger teeth even in total height. I certainly recall crown heights between 125 and 140 mm. The Black Hills (173 mm TH) and Hubbell's (129 mm?) teeth are definitely larger than the institution record from Shimada. This is even more the case for the highest lower anterior crown claimed in the study. That is a problem with meg fossils but it can't be ignored. Let akone some massive fragments of teeth at least comparable in size to some record-sized private teeth. Do we need to go out of our way to find teeth or even fragments (!) of teeth in private collections that are larger? Shimada didn’t use that specimen for no reason, the convention in palaeontology is to only work with specimens deposited in public collections with guaranteed access for researchers, we are already being pretty liberal with this rule for megalodon anyway, but at least this is justified by the significant gain in information if we do so for a complete dentition, completely unlike an isolated tooth or fragment of one, of which there is ample availability in public collections. If this is the largest in public collections, it’s still likely the largest in hundreds, if not thousands of teeth, so clearly a very large individual, as Shimada correctly noted (irrsepective of whether one agrees with his size estimates). |
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Post by Grey on Oct 6, 2019 5:10:07 GMT 5
Yes these teeth indicate really large individuals, close to the largest but not the very largest. I think there are other teeth in Museum that are larger, at least two are potentially available to science.
Same thing for the dentitions they will be available to science.
And I'm pretty sure of a lower anterior teeth much larger than the one in this study.
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Post by Life on Oct 6, 2019 8:24:22 GMT 5
Shimada remeasured the teeth but there are definitely a good count, if not many, larger teeth even in total height. I certainly recall crown heights between 125 and 140 mm. The Black Hills (173 mm TH) and Hubbell's (129 mm?) teeth are definitely larger than the institution record from Shimada. This is even more the case for the highest lower anterior crown claimed in the study. That is a problem with meg fossils but it can't be ignored. Let akone some massive fragments of teeth at least comparable in size to some record-sized private teeth. Do we need to go out of our way to find teeth or even fragments (!) of teeth in private collections that are larger? Shimada didn’t use that specimen for no reason, the convention in palaeontology is to only work with specimens deposited in public collections with guaranteed access for researchers, we are already being pretty liberal with this rule for megalodon anyway, but at least this is justified by the significant gain in information if we do so for a complete dentition, completely unlike an isolated tooth or fragment of one, of which there is ample availability in public collections. If this is the largest in public collections, it’s still likely the largest in hundreds, if not thousands of teeth, so clearly a very large individual, as Shimada correctly noted (irrsepective of whether one agrees with his size estimates). In order to have a meaningful idea about how large Megalodon could really be, it is important to take a look at private collections as well. Science does not restrict you from accessing data from any quarter, you just have to define your target population and elaborate your scheme of data collection. In this case, Grey can apply the logic of Purposive Sampling. Qualitative data collection methods are used to obtain insight that Quantitative data collection methods cannot provide. Better yet, Mixed Methods for data collection can be used. Multi-Stage Sampling for instance; quantitative first and qualitative next. Grey providing you tips for FREE.  |
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Post by theropod on Oct 6, 2019 15:38:06 GMT 5
^Well I am not the one making these rules. Most journals will tell you to stick to material in public collections e.g. e-system.app.pan.pl/app/journal/for_authors/"Science" may not restrict you from accessing data from any source, but "scientific journals" tend to impose certain standards for reproducibility, which requires specimens to be deposited in a collection where they will be reliably accessible to any researcher who wishes to study them. That is why I wrote it was "convention in palaeontology". Whether we should use purposive sampling is another question that has nothing to do with whether we’re allowed to use private specimens or not. In the attempt to find the largest possible specimen, this is warranted. Of course the question is whether the result will have any real biological importance, especially since we are seemingly now already down to talking about fragments of teeth, not even whole teeth, let alone specimens whose size can actually be somewhat reliably estimated. Obviously, size estimation is a quantitative question, and primarily requires quantitative data, at best informed by qualitative data (tooth morphology…). As regards the Yorktown and Bone Valley dentitions from the Hubbell collections, I don’t know the precise public access situation for those (the person actually studying them can certainly tell us more), but material from the Hubbell collection is quite commonly cited in studies, so it would appear there is access. |
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Post by Life on Oct 6, 2019 22:51:42 GMT 5
^^^ Hmm. That is underwhelming, but thanks for the share. I hope some journals will allow authors to discuss fossils in private collections in the 'supplementary information' part. Grey take notes, just in case. |
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Post by theropod on Oct 6, 2019 23:17:37 GMT 5
I’m sure Grey and his coauthors are well aware of this, and have made sure to comply with whatever journals they aim to publish their work in. |
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