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Post by Grey on Feb 23, 2014 23:06:59 GMT 5
For help :
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Post by theropod on Feb 23, 2014 23:07:47 GMT 5
The upper intermediate of great whites isn’t a good analogue for the third upper anterior of C. megalodon. It is proportionally tiny, and still smaller thanthe relatively smaller anteriors of C. megalodon.
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Post by theropod on Feb 23, 2014 23:14:05 GMT 5
@life: What I meant was that there was quite a difference. The left A3 on ch-31 is 78mm wide, which is smaller than the UA1 and L1, while the right A3 is 85mm wide, which makes it the second-widest tooth in that quadrant only exceeded by the L2 (which is commonly the widest tooth in the dentition).
This one is not as massive as for example Hubell’s tooth, rather like the UA3-built seen in the former.
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Post by Life on Feb 23, 2014 23:22:15 GMT 5
Yes, the tooth in question (seemingly A3) is certainly not the largest in the dentition of its owner. My intention was to identify the tooth, it is not a lateral tooth.
Leaving the rest to you enthusiasts.
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Post by theropod on Feb 23, 2014 23:31:26 GMT 5
Ah, I see. Then that was more likely referring to just one quadrant: So the percentage for the spacing is in fact 4.2%.
This doesn’t change the validity of the method though.
that was my point, by 20m he is not necessarily referring to having estimated a specimen at that size. It is apparent from what he states in his talk that he simply considers C. megalodon as most likely having approached that lenght, based on large individuals that he estimated at 18-19m.
18m is roughly what you get when using 4.2% of spacing for Hubell’s tooth, assuming it to be a first anterior (although I’m not convinced it is).
Because that’s some near-mythical 20cm+ tooth from an obscure chilean private collection, not the famous 18.4cm Hubell’s tooth that is advocated as the largest meg tooth in the world and used for illustration everywhere on the internet.
Btw where did you get the measurement from?
I guess Kent will have as well, he told me he spent time in Hubell’s collection studying shark jaws.
those are the figures I had inserted for estimation, it becomes clear if you check what calculation is written in it. The point was in estimating the size of C. megalodon, so it is that animal whose jaw-measurements have to be inserted. I think you should test that.
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Post by Grey on Feb 24, 2014 0:18:16 GMT 5
Well that again means that Mike Siversson found 19 m for Meg (with which tooth specimen ?) with 4.2% then.
Based on individual(s) that he has estimated at 19 m or bit more I'd say, not the one he estimated at 18 m like the Chilean tooth. He doesn't give absolutely precise figures but he several times stated 19 m and said close to 20 m in mails and in some articles. That's not that precise but not rough. I don't say he says he has one figure reaching 20 m but almost, which can mean a size of 19 m or a bit more.
Good to know. Now how did he get 19 m...as Hubbell's tooth is the widest we know of. There's something else we don't know.
Not mythical neither obscure, Bretton wrote me he was still in the contact with the owner of that tooth. That's only private pieces are barely available to scientific communities, remember the Spino snout discovered in 1975 but accessed by paleontologists only in the 2000's. All the paleontologists are not aware of the private giants specimens.
From Shimada :
If the specimen ('the largest tooth') is in the public domain (accredited museums) with a unique museum catalogue number, it is definitely worth publishing. However, fossil specimens that belong to private collections (e.g., including Hubbell collection) are not considered stable repositories for scientific specimens where the permanency and accessibility to specimens are not guaranteed. For a work to be considered as 'science,' all the data must be replicable and the study must be able to be repeatable by other scientists. Because specimens in private collections don't meet that standard, good scientific/paleontological journals will not accept papers in which the data are based on fossil specimens in private collections. That is why I have not studied them. If someone with the largest megalogon tooth can donate it to a public institution, than, I would be interested in writing a scientific paper about it.
From Mark Renz who handled it several times and made a life-sized picture of it in his book.
Yes, the tooth is 5.9 across the top of the base, but if you measure a little lower in the base, it's actually 6 inches.
Certainly, but all the US Meg and fossils sharks specialists have spent time to Hubbell's house^^ Brett is more focused on the phylogeny and physical constraints for Meg than studying extensively its maximum size. Here I'm interested at how Mike Siversson did his calculation for Meg, and with which tooth specimen. I suspect it is Hubbell's tooth, but not certain of this.
Fair enough a bit confusing but a good summary of the datas.
Or we ! I prefer to have all the tools in hand before test anything with absolute certainty.
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Post by elosha11 on Feb 24, 2014 0:52:12 GMT 5
This is a Peruvian tooth from Roberto Penny Cabrera's FB page. I'm fairly certain it was taken from the Inca desert, where the Megalodon skeleton is located. Looks like it's between 6.5 to 7 inches long. Any guesses from the experts here was to what type of tooth it is? I'd think it's very likely an anterior and not a lateral.
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Post by Grey on Feb 24, 2014 1:04:50 GMT 5
That's a good finding elosha. I'm not really an expert though ^^ I'm thinking perhaps a lower anterior ? It seems quite elongated.
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Post by creature386 on Feb 24, 2014 1:13:00 GMT 5
^Exactly my thought. I am terrible in identification, but I had theropod's post in mind and it doesn't really look like the classical UA I always have in mind.
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Post by Grey on Feb 24, 2014 1:21:35 GMT 5
One thought, I think we often forget that these things acually killed thousands of animal preys in a Meg lifetime...
L1 or L2 ? If true, determining the crown height and the tooth width would be interesting.
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Post by creature386 on Feb 24, 2014 1:30:01 GMT 5
Using my ruler, I got a width of a bit more than 4 inches (assuming it is 6.5 inches long in slant height, I actually got 4.1 inches, but given that my measurements are always very rough, this would be lied precision).
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Post by Grey on Feb 24, 2014 1:39:33 GMT 5
Using the Yorktown dentition as template, if that tooth is a LA1, it means the width of the UA1 could be about 130 mm wide. Based on the LA2 of the same dentition, it means the UA1 would be about 120 mm wide.
Nothing very precise but if it's a L1 or L2, that represents possibly a good-sized Meg, but we've seen hints of bigger ones. Now, like I often recall, that tooth was only shed by a shark which was still growing at the time.
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Post by theropod on Feb 24, 2014 2:27:41 GMT 5
He always seems to have precised that to be 19m for the biggest individuals. museum.wa.gov.au/explore/videos/rise-super-predatory-sharksThe problem is that the methodology is not properly documented (in the case of C. megalodon, his main field of research appear to be Cretaceous sharks on which he published many actual papers), they are rough (see the quote), and they fluctuate. We don’t know much about what he did, so as long as we don’t, why is it so important? For all we know, they could be guesses, or based on some simplyfied ratio (I recall there was such a thing for jaw perimeter). We do not know for sure. That’s part of what your quote from Shimada is about, documentation and replicability of information. In any case, we have regressions that can reliably estimate total lenght from toothrow lenght in extant sharks. We can also quantify the degree to which toothrow lenght fluctuates to a good extent (and if only by rough measurements of photographed jaws). But these data already tell us a lot. Their variation is no worse than the individual variation affecting results from any other method (in fact, looking at how tooth widths fluctuates considerably and tooth height must be even worse, it’s likely better), and they don’t have biases resulting from the use of single teeth, which have differences in relative size between C. megalodon and C. carcharias. No, but Hubell’s tooth is the megalodon equivalent of MSNM v4047. It’s the epithome of huge megalodon teeth, although it’s not as open as we’d all whish for. On the other hand, I haven’t yet heard a mention of that chilean tooth anywhere, let alone a measurement. Absolutely. However I’m sure you don’t think we should disregard that tooth, if its measurements are reliable. I’m quite certain Siversson also wouldn’t ignore it in his talks, and I’m extremely certain he knows of the tooth’s existence. Thank you, it can be exhausting to search through such a long thread when you don’t know any more whether and where exactly something was posted. It’s the maximum root width we need. It’s size is part of those physical constraints. Anyway, it does not seem realistic he would have reached his size estimates with a specimen smaller than Hubell’s tooth, so let’#s just assume he used this one in the high probability thereof and the absence of better data.
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Post by theropod on Feb 24, 2014 2:46:20 GMT 5
18.3cm along the longer slant, 17.7 along the shorter, 11.9cm in maximum width, 15.8cm in crown height, 17.4cm in perpendicular height.
That specimen is very elongate and it seems to have an almost disproportionally long crown. It’s certainly big, how big exactly the specimen may have been is a matter of position. I think an anterior mandibular one is possible, but also perhaps an upper L1 (albeit a relatively slender one, like that on the right of CH-31). It appears to be somewhat inclined to one side.
The latter would predict a summed upper tooth width of 247cm, the former a summed lower tooth width of 215-235cm.
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Post by Grey on Feb 24, 2014 3:09:45 GMT 5
"About 19 m" to be exact. Which might indicate he got something just around 19 m, and in several articles and interviews he reported "almost", "close" to 20 m. Either he got precisely 19 m or a bit more. Hence the almost 20 m. I really don't think it's really rounded around 18-20 m. From his YT talk : I've done the calculation with a number of teeth and the largest number I come up is about 19 m.They could reach close to 20 meters, that's my opinion.Or from an article in the Western Australian Museum This extinct group of apex-predators is thought to have given rise to Otodus megalodon or Carcharocles megalodon - a nearly 20-metre-long behemoth that spread terror through the oceans until its extinction about two million years ago.This suggests the precise highest number he got in his calculation was 19 m or slightly more. He focuses on Cretaceous lamniforms but studies extensively their evolution during the Cenozoïc too. It is interesting (rather than important) to know what was his exact calculation, which tooth size he used. As he says "the latest estimates" support that he proposes one of the most modern size estimate for megalodon. I just try to know how he found such a size estimate of about 19 m. That's no guess from him, he precisely said the method is based on jaws perimeter, and apparently not only with the great white. He simply uses this method too on the Cretaceous sharks he extensively studies. Here he estimates Hubbell's set : If you measure the total upper tooth width here and compare it for example that of the white shark, mako shark or porbeagle shark, this particular individual was in the order of 12 m, maybe 11 to 12 m.He gets something at 11-12 m whereas using what we know (toothrow+4.2%+Lowry's formula) we get 9.85 m. There's something we're missing. As he's the only modern paleontologist who uses this method to estimate the largest size in Meg and report it in his talks, articles and discussions, it's worth to know how he did exactly. I'm not talking about the material he used but how he performed his calculation to get that figure. I don't deny that. But I say that we ignore some points used in that method. 4.2 % of spacing doesn't allow to get the same sizes estimates Siversson calculated for the largest Megs. It doesn't allow either to get the 5.50 m TL white shark from boneclones as 4.2 % added to the toothrow yeilds only 4.62 m TL. 4.2 % is not enough or we don't know something else in the calculation. That comparison is accurate. Regarding the Chilean specimen, this just proves how private pieces are difficult to reach. But Brett Kent saw it and said it was the most gigantic one he saw. Brett Kent is an experienced sharks teeth researcher. No one knows his measurements only certainly its owner. I think too. But did he really use it in his calculations ? With its actual measurements ? How exactly ? That's the whole point. You welcome, the thread becomes massive indeed. Well, that's the widest confirmed tooth I know so far and as it is famous, it is worth to work on it and determine what were the proportions of the beast which possessed it few millions years ago. Yes but he did not propose any estimate of his own (except for my all first mail from him, where he wrote me the gigantic Chilean tooth he saw suggested a Meg of 20 m or a little more plausible). He studies methods but does not focus on. Assumption is not enough to me ! At one time he responded me but so far I've got no response. Perhaps angry at me... On occasion, I'd suggest you if you're interested to get a confirmation to contact him.
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