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Post by Grey on Nov 20, 2019 14:57:23 GMT 5
Excuse me sam1, but there are certainly expérimented amateurs thzt know more than professionnals. Technically yes, I and my co-authors, and probably Mike Siversson and Bretton Kent know a bit more about the relationship between dentition and body size in megalodon : 15-16 m was probably a normal good-sized individual, depending the region and/or time. There is no contest to this, theropod, blaze, coherentsheaf,Life and elosha know actually a bit more about this than Shimada and probably other guys well aware of the study. And I have actually discussed and highlighted Shimada, he is now well aware of it and may accept the new estimate. It is a near certainty, some members of the megalodon species may have reached 20 m, making it an unique evolutionary occurence and the only macropredator eating warm-blooded prey confirmed to reach the symbolic mark of 20 m (except for the slender Basilosaurus). There is no doubt, megalodon and Livyatan possibly outclasses any other apex predators before or since because of singular events to their era. Man..now you excuse me, but I definitely take Shimada as bigger authority on the subject than you. And what, are you suggesting it didn't occured to him to choose between the anterior and lateral method? That he did not have actual reasons for his decision?? From what I understand (correct me if I'm wrong) his rationale went along applying the GWS average/maximum teeth/TL analogy. The obvious thing is, a GWS jaw is typically a showcase of differently sized anterior teeth that are almost never aligned and placed in perfect order. And there is often an anterior utlier that sticks out in shape, position, and size. I may be merely speculating here, but this characteristic seems less pronounced along the lateral part of the jaw. So taking one isolated tooth and simply extrapolating from that does not look like a realistic method at all..it doesn't take into account that if megalodon was anything like the GWS, or any other shark for that matter, it had wildly different teeth within the jaw. And the only way to go is to take a holistic approach and make conclusions from that. I'm sure there are some isolated GWS teeth that would, by limited estimation methods, suggest a much greater maximum size than what is actually scientifically confirmed. p.s. apologies for derailing and hijacking the thread. You can move this discuasion to a more appropriate one Sam1 have you discussed with Kenshu Shimada ? I have and I can tell you for sure that in that particular field (methodology to estimate size) yes he knows less than members of this board. You simply don't realize that he NEVER looked at our method until recently. Not only that but he is probably gonna collaborate with my coworkers. Shimada is a professionnal which means he simply did not have the time or opportunity to see the caveats in his method. It is not the first time this appears, how many 'amateurs' did really help specialists in a number of cases (SVPOW...). Unless the largest great whites and megalodons specimens had teeth that stopped their growth (but how would this affect the size of the toothrow is unclear), no it is unlikely to find a GWS tooth that will suggest more than 15-16 m... while even not particularly large associated dentitions suggest a range of 14-17 m. Realize that those results by Shimada latest article are virtually known by members of the board since years. And I have named professional scientists who are more aware of the best progress in this field. Shimada's method has problems that were already noticed even before its first publication, in the 1999 paper on Parotodus by Brett Kent. Theropod, did not you recently agree that megalodon whatever the actual method may have reached 20 m at some point, I did not say something different and the percentage I use is symbolic, not mathematic. The 200 tonnes Plagne trackmaker has been dismissed IIRC (why the need to use this as comparison ?), 20 m TL megalodons have not. Anyway for now you have more faith in Lowry's method added to the few details you try to suggest. Our method is still including new parameters so we will see how much weight it has gained by the end. Either using the largest/widest teeth known, and the various methods proposed since a long times using dentition or tooth width, 18 m is pretty secure at this point, unless you give more weights to the crown/tooth height based method. But if there is really a secure TL for one specimen at this stage, I'd say 14 m, simply based on the likely very conservative vertebra based method by Gottfried which applied to the 230 mm centra. An estimate that could even be 16 m if Pimiento's not published yet observations of the Belgian backbone are confirmed. Coherentsheaf said this without taking into account the Belgian specimen which likely measured at least 10 m... So a size of around 15 m is already pretty likely as a whole and does not appear like an upper size range for the whole species. Regarding body mass, this vertebra, comparing with GWS with BM and centra diameter reported on elasmollet, suggests the shark with it may reasonably have massed between 30 and 40 tonnes. All in all, it is not certain but likely that the meg species did reach 20 m at some point. I think there is no need to ponder about that. |
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Post by theropod on Nov 20, 2019 21:16:13 GMT 5
I don’t think that’s what Sam meant, as he said "isolated GWS teeth" that would "suggest a much greater maximum size". He is likely to be correct in that, though I don’t know any such specimens (nor any reported measurements for isolated large extant white shark teeth), as there is still significant variability even in jaw perimeter, and individual tooth heights are likely even (much) more variable. There could easily be some great white shark teeth that would suggest an 8 m shark on their own when using mean proportions, but in the jaw of a 5 m one.
You are talking about megalodon specimens not suggesting larger sizes than 15-16 m based on any great whites, although this is likely also wrong, did you forget that Gottfried et al. estimated their infamous 20.2 m figure using precisely that method?
I did and I do.
What I take issue with is simply the spectacularly wrong claim that this is certain, which was what you initially claimed. Something like "symbolic percentages" doesn’t exist, it is plain poor practice to make up a wrong and misleading percentage just to make an exaggerated point.
Proper scientific wording would be "it is probable" (i.e. has a greater than 50% chance to be true), given that it really is (i.e. if the mean estimate suggests something, making it our expected value, making it reasonable to say that it more likely than not reached it, assuming a close to normal distribution).
"May have reached" is even more vague (but at least not wrong), as it says nothing about the precise probability, merely that it isn’t exceedingly low.
I do not understand what you are trying to say here, are you telling me what I have more faith in?
It has? Source?
The need to use this as a comparison? You claimed to be 90% certain 21m+ megalodons exist based on a few isolated teeth, so I took it you would also be 90% certain 200t sauropods exist based on a few footprints (a pretty good comparison, note those footprints are 1.5 m wide, while megalodon teeth are at most around 17 cm tall)…
I take no issue with that, didn’t you see me propose 16 m in my last post? Although for different reasons, as that method, once more, doesn’t produce a certainty (or did you find a prediction interval based on vertebral diameter)? As I also mentioned in my last post, 14 m is around the lower end of the 95% prediction interval for the largest teeth based on jaw perimeter data). So yes, it is reasonable to say we are certain of that (as always within the context of assuming great white shark-like proportions), as the probability of the size being lower is only 2.5%, at least given the jaw perimeter is correctly estimated (4536 mm based on the tooth being 25% wider than the one in the Yorktown specimen whose dUJP you guesstimate at 3700 mm). Of course variables such as whether the perimeter estimate is actually correct, and whether the proportions are actually following those of great whites would make the real probability much higher, but yes, for now I’d be pretty fine with saying it is certain it grew to over 14 m.
There’s a big difference between claiming at least 20 m is certain and at least 14 m is certain, I don’t think you need to be reminded of that.
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Post by spartan on Nov 20, 2019 21:45:48 GMT 5
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Post by 6f5e4d on Nov 20, 2019 22:52:27 GMT 5
Livyatan can win this fight, as its far larger and stronger compared to Pliosaurus.
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Post by Grey on Nov 21, 2019 1:43:00 GMT 5
Theropod, we are agreed since the beginning, you just need to correct me technically at each general and/or symbolic statement I write. You're as cool as a pain in the ass to communicate, I guess that what makes discussion cool anyway.. somekind of Greg House of paleontology haha
However, it is not more unlikely to have a 21 m hot-bodied fish as cold blooded fishes have already reached or closely approached that length, while there is absolutely none full grown blue whale sized land animal remains to have been found, I remember this SVP abstract saying this trackmaker may have been in the confirmed upper range of the gigapods.
There is nothing terrestrial even approaching 200 tonnes that we have material from while we have teeth from megalodon likely suggesting jaws that would correspond in relation to the body to a white shark as large or a bit larger than the cold blooded Leedsichthys and Rhincodon which are heavily suspected to tip the 20 m mark.
But again overall we're agreed.
I would say that the very existence of Livyatan, which almost certainly measured at least 15 m and was an apex predator reinforces the estimated similar TL of another hypercarnivore at the same time, the big shark as it shows an active carnivore that size, much larger and more massive than any predatory marine reptile known so far, could exist at all. Just like the whale shark size possibly allows a minimum max size for megalodon while the largest sperm whale (21 to possibly 24 m) could represent an upper length for Livyatan. Or any toothed marine tetrapod for that matter.
I also think of an article on elasmoshark where a guy theoretically estimated the maximum body size of the body of a white shark to be 15 m. That is a rather old article and I would not be surprised if update data could say more, I think it used only one parameter such as oxygen filtering.
But at least it confirms that a carnivorous white shark-like creature can actually breathe. So this is another reason to think 15-16 is pretty certain, and that we have to admit few apex predators may have approached such a girth, only Livyatan seems to propose something comparable.
And then we can't ignore that numerous teeth, even if there error bars, indicate we may have at least some specimens coming from sharks that were at least as large as any whale shark can grow. Which is larger than confirmed large pliosaur for Denis.
And one of the few isolated centra suggested a fish of a minimum ~14 m long, which is already whale shark-size and larger than any confirmed macropliosaur. This is a possible underestimate.
Basically the whole thing is that I probably tend to transform too much "likely" in "certainty".
I think I'm an optimistic individual all simply.
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Post by 6f5e4d on Nov 22, 2019 8:51:26 GMT 5
I've voted to say that the giant whale Livyatan would win if it fought Pliosaurus, since the whale may be somewhat heavier than the pliosaur.
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Post by Grey on Dec 2, 2019 19:33:51 GMT 5
I've voted to say that the giant whale Livyatan would win if it fought Pliosaurus, since the whale may be somewhat heavier than the pliosaur. Most likely much heavier. Livyatan has a skull length of 3 m and a width of about 2 m, there is no pliosaur comparable to this. What is commonly referred as a "large" pliosaur is a specimen with a skull at least 1.8 m long. Scientifically stated, there is no 3 meters long pliosaur skull anywhere, not even fragmentary. Not to say it won't happen but after two decades of discussions about semi-mythical accounts of giant pliosaurs, Kronosaurus and Sachicasaurus represent what is the most impressive in terms of cranial dimensions... and none of those decisively exceed 12 m in TL. Of course, a 10-20 tonnes pliosaur would still be very risky to tackle for anything that ever lived and Livyatan probably would have been cautious in presence of this reptilian breather. |
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Apex
Junior Member
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Post by Apex on Dec 3, 2019 23:36:43 GMT 5
Hi guys
Sorry to interrupt this thread
But it's been a while since I've read up on prehistoric macro predators so I'm a bit out of the loop
Just a few questions
What was the currently largest estimated pliosaur and how big was it? (I still remember the 25m liopleurodon estimate haha)
I heard something about some large macropredatory ichthyosaurs bigger than even the pliosaur, is that true?
Is that skull from the allegedly 25m long sperm whale valid or has it been debunked again?
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Post by dinosauria101 on Dec 3, 2019 23:46:07 GMT 5
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Apex
Junior Member
Posts: 207
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Post by Apex on Dec 9, 2019 23:17:49 GMT 5
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Post by theropod on Dec 9, 2019 23:36:57 GMT 5
Hi guys Sorry to interrupt this thread But it's been a while since I've read up on prehistoric macro predators so I'm a bit out of the loop Just a few questions What was the currently largest estimated pliosaur and how big was it? (I still remember the 25m liopleurodon estimate haha) I heard something about some large macropredatory ichthyosaurs bigger than even the pliosaur, is that true? Is that skull from the allegedly 25m long sperm whale valid or has it been debunked again? By skull, you mean the nantucket jawbone? theworldofanimals.proboards.com/post/32366That’s more likely a ~21 m sperm whale. 25 m is very unlikely for this specimen. The currently largest pliosaur depends on what you consider valid. The Oxford mandible would be the largest substantial specimen if its size were legit, but it has been severely called into question on the grounds of likely being restored too big. There is a very large mandibular symphysis in the NHMUK that might come from something similarly large or even larger, but that is a fairly small fragment and its taxonomic assignment uncertain (whether we get exceptional size estimates for it heavily depends on the analogue and the metric used for comparison). There is the peterborough vertebra, which also may have been from a larger specimen, but it’s not even confirmed that it’s a pliosaur and not a sauropod (would help if someone bothered to figure and properly describe it). The Monster of Aramberri appears to be the largest definite pliosaur in terms of vertebral diameter, but once again that is a small and rather unreliable metric to scale it on (but the specimen is rather substantial, so if the teams working on it can sort out their difficulties we will at some point have a more exact idea of its size). Apart from that, Sachicasaurus (holding the distinction of having the largest complete skull of any pliosaur), Kronosaurus and Pliosaurus funkei/ macromerus, all likely around 10-11 m long and about that many tons in weight. And yes, there are macropredatory ichthyosaurs that grew bigger than these pliosaurs, at least two, Himalayasaurus tibetensis (which is essentially the same size as Shonisaurus popularis) and an unnamed lower Jurassic probable Temnodontosaurid from Europe. |
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Post by kekistani on Dec 10, 2019 2:33:31 GMT 5
Hi guys Sorry to interrupt this thread But it's been a while since I've read up on prehistoric macro predators so I'm a bit out of the loop Just a few questions What was the currently largest estimated pliosaur and how big was it? (I still remember the 25m liopleurodon estimate haha) I heard something about some large macropredatory ichthyosaurs bigger than even the pliosaur, is that true? Is that skull from the allegedly 25m long sperm whale valid or has it been debunked again? ) and an unnamed lower Jurassic probable Temnodontosaurid from Europe. Wait, what? A Temnodontosaur larger than a pliosaur? Christus |
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Post by theropod on Dec 10, 2019 2:40:57 GMT 5
Yes, probable 14-16 m temnodontosaurids are attested to by fragmentary material from both the Hettangian or England and the Toarcian of Southern Germany. Of course those remain very poorly known…
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Post by kekistani on Dec 10, 2019 3:25:26 GMT 5
Yes, probable 14-16 m temnodontosaurids are attested to by fragmentary material from both the Hettangian or England and the Toarcian of Southern Germany. Of course those remain very poorly known… Holy christus that is massive! And being a Temnodontosaur it would probably be an active predator,right? |
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Post by theropod on Dec 10, 2019 3:40:00 GMT 5
There are some very large isolated teeth, bigger than any other lower Jurassic ichthyosaurs, that do suggest an actively macrophagous ecology, yes. Even Temnodontosaurus trigonodon is a serious predator, with other ichthyosaurs having been found in its stomach contents.
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