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Post by elosha11 on Apr 7, 2018 19:34:41 GMT 5
Thanks for the update Grey. So the Yorktown/Aurora specimen has been downgraded a bit? I thought excluding the outliers yielded close to 18 meters, per the published analysis by Leder et al. Was there some change in underlying calculations or methodology? Still if these calculations are correct, it was still quite a large individual at 16.68 meters. If you consider this as a "holotype" it probably was longer than the Livyatan holotype, which I think more reasonably fits in the 15-16 meter range rather than the extremes of 13.5 or 17.5 meters.
Great to hear there's progress on the Chilean set. It's my understanding that it's slightly larger than the Yorktown set, but not a huge difference. Is that still your understanding as well? If so, I'd probably guess it will be a bit longer than Yorktown specimen, but not a huge difference. Based on the enormous length/width of some of the teeth you've posted on this thread, I'd agree with you that it strongly suggests Megalodons substantially longer/bigger than the Yorktown and Chilean ones. But no doubt these two specimens also represent full grown - and perhaps above average size - adults. It's like comparing a 16-18 foot great white, which is a large adult, but still not max size, to a 20+ footer.
I hope the September meeting also leads to an even more comprehensive and peer reviewed publication. This is a methodology that really needs to be advanced/defended as the most accurate way yet discovered to measure Meg's size.
So interesting that the juvenile Bone Valley Meg already yields 11.44 meters under this methodology. Just show's how skewed "averages" can become when you use the mean, as Pimiento, et al did in their study determining the mean of all Megs was only 10.5 meters. And people took that to downgrade the overall size of the shark, not realizing that the "average" adult was much bigger than this. Just a complete misunderstanding of basic statistics.
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Post by Grey on Apr 7, 2018 19:55:46 GMT 5
No the outliers were not included, and the measurements were tweaked. Including the outliers, the mean estimate is 17.2 m. 18 m is actually the mean of all the basis specimens, including makos. The maximum size using upper dentition is 21.37 m and the minimum is 15.10 m.
All in all, the Aurora meg appear to be comparable or slightly larger in length than the Livyatan holotype and contrary to the later, there are definitive and numerous direct evidences of sensibly larger individuals. A few examples can be represented by :
• Hubbell's big upper anterior tooth which has reported a CW of 134 mm (the Aurora corresponding tooth is 108.5 mm in CW).
• a massive lower anterior tooth from a French source that is 115 mm in CW (compared to 98 mm in the Aurora dentition).
• an absolutely massive lower lateral tooth that I recently saw with a CW of 123 mm and that would correspond to lower laterals that are 84-92 mm in the Aurora specimen.
Of course, a variation is possible but this is definitely indicative.
Victor told me the Chilean is definitely larger so he's gonna measure it again.
He definitely agrees that the CH method is inappropriate while used on megalodon but useful on Carcharodon.
Now remember that according to Gottfried table, a juve meg could be as large as 14 m TL anyway.
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Post by elosha11 on Apr 9, 2018 22:33:36 GMT 5
^In your discussions with Sam1, you should post on Carnivora some the pictures of the huge teeth you posted around pp. 50-51 of this WoA thread. There are probably quite a few more huge teeth that you posted on other pages as well, but I haven't had the time to go through this whole thread again.
Under you and your colleagues analysis, such teeth could (cautiously since they not part of an associated set) be used to predict Megs quite a bit bigger than either the Yorktown/Aurora or Chilean Megs.
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Post by Grey on Apr 16, 2018 4:23:28 GMT 5
An interesting tooth that puts insight about possible maximum size.  It is owned by a Belgian collector and is from Summerville. That tooth has a crown width of 123 mm (and root width of 130 mm). I suggest most likely a lower lateral 7 position, see the Bone Valley dentition : www.elasmo.com/genera/pics/neogene/ds1001-web.jpg In the Bone Valley juvenile dentition (estimated as coming from a ~11.4 m meg), the same tooth is 65 mm in crown width. In the Aurora adult dentition (estimated as coming from a ~16.7 m meg), the same tooth is 92 mm in crown width. If the position I suggest is accurate, if the dentition based method is accurate (the figures here are the most conservative in the data) and if scaling tooth size tells anything, based on the two other specimens, we're looking at a potential 21.6-22.3 m specimen. |
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Post by Grey on Apr 22, 2018 16:51:27 GMT 5
There is an exhibit in Zurich with a partial meg skeleton, the skull, 37 teeth and some vertebra. The piece is 4.5 m long and may have come from a 10-12 m young animal according to the Museum.
I post pictures later.
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Post by elosha11 on Apr 22, 2018 22:47:51 GMT 5
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richard
Junior Member Rank 1
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Post by richard on May 23, 2018 19:46:21 GMT 5
Just wondering, all this would in fact make Megalodon the largest fish ever wouldn't it? Neither Leedsichthys or the whale shark could reach the upper size estimates of Meg.
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Post by Grey on May 23, 2018 21:12:02 GMT 5
Leedsicthys is usually considered as the largest bony fish.
Ferrón 2018 suggests its maximum theoretical body mass to be 44.9 tonnes.
This is indeed below than megalodon body mass predictions which are 48-103 tonnes (Gottfried 1996) for a 16-20 m shark but a similar work from Randall could suggest as well 34-74 tonnes, 100 000 pounds (Renz 2002) for a 18 m individual or 50-60 tonnes for a 18-19 m meg(Siversson 2012, lecture talk).
Even favoring the lower estimates would suggest larger mass estimates for meg, the largest predicted body mass for any macropredator, it would appear to be heavier than the biggest possible ectotherm bony fish.
But I'd like to see Ferrón et al. performs a similar work on megalodon than what they did for Leedsichthys.
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Post by marsupial on May 30, 2018 16:35:11 GMT 5
What is the length range for adult mega tooth shark?
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Post by Grey on May 30, 2018 19:33:50 GMT 5
What is the length range for adult mega tooth shark? Depends which author, which method and which specimens you use. Gottfried and Compagno (1996; 2001) considered a mature specimen could range from 11 to 20 m, but an immature could grow as large as 14 m. Using vertical tooth height of a 168 mm tooth, they determined the shark could range 16-20 m, but recognized that larger teeth exist in private collections. Estimates based on tooth width give a slightly larger but just as variable size range. Estimates using the combined width of the whole dentition are at work, may be published soon and will give more stable and consistent estimates. The problem I see with the classic conservative 16 m TL based on the 168 mm high, 125 mm wide tooth is that measuring the proportions of GWS dentitions and naturally preserved megalodon dentitions, a 16 m meg with 125 mm wide upper anteriors would have a dentition more than 20 % larger/wider than a typical scaled up 16 m white shark. This would imply a shorter but extremely stout and stocky shark, even more so than what is suggested by Gottfried 1996, something that it seemingly not indicated by the structure of the vertebral remains. This tend to suggest that particular tooth most likely came from a shark larger than 16-17 m. |
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Post by prehistorican on May 31, 2018 2:13:42 GMT 5
I remember coming across coherentsheaf's drawing of Megalodon, is it accurate? I believe at parity a large female Megalodon would have a combination of both more fat and more muscle than a great white.   |
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Post by prehistorican on May 31, 2018 10:52:01 GMT 5
Hypothetical Megalodon I quickly sketched based off of Coherentsheaf's base shape of the Megalodon. This is how I think a large O. Megalodon specimen could have looked: stocky, large eyed, large gilled, crescent shaped tail, thick keeled, battle scarred, etc.  |
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Post by Grey on May 31, 2018 14:50:30 GMT 5
Definitely valid.
I would recall that as animals become huge, eyes usually decrease in size or at least don't become larger.
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Post by prehistorican on May 31, 2018 20:09:45 GMT 5
True, blue whales and sperm whales have small eyes for their size. I guess my depiction of Megalodon didn't make them too big, or maybe they did, not sure.
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Post by Life on Jun 1, 2018 21:46:23 GMT 5
Decent art there. However, I disagree with the gills aspect - Megalodon isn't Basking Shark or related.
Megalodon would have gill structure similar to that of great white shark.
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