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Post by creature386 on Oct 2, 2013 18:05:34 GMT 5
Remember that the paper said it is not known whether Megalodon caused that bite, it is even possible that it was not a shark (although it is unlikely that it was something else than a shark, due to the jaw shape).
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Post by Grey on Oct 2, 2013 18:30:57 GMT 5
The authors count several types of potential agressors, sharks and odontocetes. An odontocete is not impossible but far less likely given the shape of the bite. As for the sharks, that's open, but given the well known associations of megalodons teeth with whale bones, often with teeth marks, the superior propencity of meg to target balaenopterids preys items and the fact the authors report juvenile megs teeth in the same area, it seems quite more likely to me that the culprit was a young meg.
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Post by Deleted on Oct 3, 2013 22:34:10 GMT 5
I give it to the Megalodon due to speed, agility and deadlier teeth.
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Post by Life on Oct 11, 2013 19:37:18 GMT 5
Remember that the paper said it is not known whether Megalodon caused that bite, it is even possible that it was not a shark (although it is unlikely that it was something else than a shark, due to the jaw shape). That study actually concludes that a shark is responsible for this incident; other suspects have been mentioned in the study but they have been dismissed within it. Godfrey (an author of the referred study) is himself convinced that the aggressor in this case was a shark: www.macroevolution.net/carcharocles-megalodon.html#.UlgLWVCmEr4Now, I am not aware of any shark who would take chances against such a big whale. Only a megatoothed shark fits the bill realistically.
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Post by theropod on Oct 11, 2013 20:16:47 GMT 5
There are several possibilities (unsurprisingly only sharks), and I'd also recommend taking size figures based just on pathologies with a grain of salt, however I'd say small/juvenile C. megalodon (or perhaps large adult Parotodus?) are by far the most likely attackers due to their behavioural patterns.
Based on root width the shark would have been ~8m long in total.
A damn bold kid indeed.
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Post by creature386 on Oct 11, 2013 20:23:24 GMT 5
Remember that the paper said it is not known whether Megalodon caused that bite, it is even possible that it was not a shark (although it is unlikely that it was something else than a shark, due to the jaw shape). That study actually concludes that a shark is responsible for this incident; other suspects have been mentioned in the study but they have been dismissed within it. Godfrey (an author of the referred study) is himself convinced that the aggressor in this case was a shark: www.macroevolution.net/carcharocles-megalodon.html#.UlgLWVCmEr4Now, I am not aware of any shark who would take chances against such a big whale. Only a megatoothed shark fits the bill realistically. As I said in the brackets, I have recognized that something else than a shark is unlikely & I too believe that it was a megatoothed shark.
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Post by Godzillasaurus on Oct 16, 2013 5:00:36 GMT 5
Does anybody have any reliable sources that state the TRUE weight of megalodon? We have seen some overly ridiculous size estimates, ranging from 60 tons to 100+ tons. Honestly, even 60 tons for a 55 foot (at maximum!) cartilaginous fish is preposterous. Megalodon is by far one of the most overrated animals ever
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Post by Grey on Oct 16, 2013 9:14:19 GMT 5
Does anybody have any reliable sources that state the TRUE weight of megalodon? We have seen some overly ridiculous size estimates, ranging from 60 tons to 100+ tons. Honestly, even 60 tons for a 55 foot (at maximum!) cartilaginous fish is preposterous. Megalodon is by far one of the most overrated animals ever 1. How do you expect to know the true weight of an extinct creature known (officially) only by isolated teeth and centras ? Even when complete skeletons are known, weights estimates are still subject to fluctuations. T. rex is known by several skeletons and we don't know with 100% of certainty how much it weighed. We merely have a good idea of it. 2. All the published estimates are not ridiculous but based on assumptions extrapolated from living lamnids/lamniforms. I guess you criticize without having even read the published papers about megalodon. 3. You cannot judge an animal as "overrated" when your very basical questions just show you have not performed serious research about it. Actually, a number of people, not that interested in sharks research, have premature judgements and cannot understand that megalodon was really big. Much bigger than any pliosaur known to date. Now if you want to read about weight estimates, read Gottfried et al. (1996) about rigorous estimated figures based on the size relationship in the modern white shark (ftp://swfscftp.noaa.gov/users/hdewer/Petitions/ca%20petition/Attachment%204.pdf) but you can also read the many mails I've got from various researchers in the thread dedicated to megalodon size, showing various interpretations. Briefly, anything between 50 and 100 tonnes is possible for a the max weight of megalodon, all depending the true physiology, the phylogeny and various factors like the size of the liver (1/4 the total body mass of a great white), gender, quantity of food in stomach... And yes, sharks can be very heavy for their size and megalodon was certainly huge, whatever its exact proportions. Basically if you want to have a very rough idea of the weight of a megalodon, you have simply to use the weight of modern lamnids or lamniforms as template. Using white sharks proportions, for a 18 m (possible size) megalodon you get EASILY weights over 60 tonnes. At last, wikipedia has good references as well. Basically, the only and so far, best published data we have about megalodon's weight is from Gottfried et al. Rigorous, not certain, but certainly not ridiculous.
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Post by theropod on Oct 16, 2013 16:07:29 GMT 5
In fact scaling from an average great white shark you get exactly 60t for an 18m shark (51 for 17m, 71 for 19m), which is in agreement with Siverson´s figures, even tough we don´t know how he estimated them. Gottfried´s regression produces rather high results, the one from Casey & Pratt (1985, page 11 of the great white symposium) are significantly lower (81 vs 103t), the same goes for direct scaling.
Any too definitive claims are certainly premature at now, that is, until the peruvian discoveries get described.
But I tought Carcharodon was such a terrible model for C. megalodon?
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Post by creature386 on Oct 16, 2013 17:43:54 GMT 5
Megalodon is by far one of the most overrated animals ever Not at all, many people (at least on YouTube) believe it is impossible for it to have been longer than 50 ft. But I tought Carcharodon was such a terrible model for C. megalodon? From what I have read in Renz's book, Kent believes a basking or a whale shark to be the best model for C. megalodon, when it comes to bulk. Scaling from a 12,6 m/21,5 t whale shark, I get following results: For a 15 m shark=36 t For a 17 m shark=53 t For an 18 m shark=63 t For a 20 m shark=86 t These numbers are somewhat lower than the one given by Gottfried, but that's because I haven't included a possible increase in bulk (I didn't do so, because some posters said we don't have enough evidence). I don't recomment you to use these numbers (but I don't think anyone wanted to do so).
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Post by Grey on Oct 16, 2013 18:28:59 GMT 5
A lamniform in general is a good model. Anything between a basking, a white or a mako can be good.
But as pointed in Pimiento, despite the differences in phylogeny, the white shark is considered as the best modern analogue for megalodon.
In his talks, Siversson indeed estimates a weight if it was built like a white shark, a bit more than 50 tonnes, maybe 60 tonnes.
Kent also suggests that 50-60 tonnes is reasonnable but he does not refute Gottfried as this remains the best data. Given the various proportions in individuals of a same species, who knows... Gottfried is based on the increasing bulk observed in white sharks as they grow.
Kent said he uses the basking shark for his model of megalodon but in his last mail he said otherwise :
Hard to say for sure, but I don't think meg and Cetorhinus centra are all that similar. The large meg vertebrae I've seen are pretty robust. They don't have the more tightly packed septa of the lamnids and odontaspids, but overall they're much more solidly built than those of Cetorhinus. The vertebrae of Cetorhinus are so poorly mineralized that they are almost always badly distorted during fossilization. It's very rare to see this type of distortion in meg vertebrae.
Simply, megalodon was built like a lamniform shark, its vertebras indicate a robust fusiform body.
If it really reached 18 m (very likely), the 50-60 tonnes mark was almost certainly reached or exceeded...
This is quite difficult to imagine such a large shark really existed.
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Post by creature386 on Oct 16, 2013 19:05:05 GMT 5
A lamniform in general is a good model. You mean a cursing lamniform, right? (because Kent also said that sharks with a body adapted for acceleration, like the sand tiger shark, are a bad model)
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Post by Grey on Oct 16, 2013 20:03:07 GMT 5
A lamniform in general is a good model. You mean a cursing lamniform, right? (because Kent also said that sharks with a body adapted for acceleration, like the sand tiger shark, are a bad model) Yes of course. A megalodon with an Odontaspis-like tail and body structure couldn't actually swim at all.
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Post by theropod on Oct 16, 2013 21:47:38 GMT 5
The numbers based on basking sharks (18m-63t) are pretty close to those derived from both the equation (18m-57t) in the paper I posted (which merelyhas a bigger sample than Gottfried et al. [1996] and should thus be preferred) and the direct sizing based on the average from Elasmollet (18m-61t). Gottfried actually appears to be the odd one out.
Approximately 60t at 18m seems to be a pretty good value, despite the uncertainities.
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Post by creature386 on Oct 17, 2013 1:45:09 GMT 5
But as pointed in Pimiento, despite the differences in phylogeny, the white shark is considered as the best modern analogue for megalodon. What do you mean by "despite the differences in phylogeny", we have no modern animals which are more closely related (no modern otodontids). BTW, body shape and bulk is the most important thing here, not morphology in general. Hard to say for sure, but I don't think meg and Cetorhinus centra are all that similar. The large meg vertebrae I've seen are pretty robust. They don't have the more tightly packed septa of the lamnids and odontaspids, but overall they're much more solidly built than those of Cetorhinus. The vertebrae of Cetorhinus are so poorly mineralized that they are almost always badly distorted during fossilization. It's very rare to see this type of distortion in meg vertebrae. I remember having read something similar in Gottfried's paper (it was not when talking about the weight estimates, it was talking about the vertebrae from Antwerp). Overall, Megalodon vertebral centra are less elongated, they have thicker walls and smaller holes in the center (I posted that for the ones who are interested). If it really reached 18 m (very likely), the 50-60 tonnes mark was almost certainly reached or exceeded... This is quite difficult to imagine such a large shark really existed. I agree (on both).
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