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Post by creature386 on Mar 3, 2014 20:22:23 GMT 5
Thanks for the correction, I thought 18.4 cm would just be the slant height measurement for the 16.8 cm tooth. As for Betucci's tooth, I remember someone on carnivora has shown a more detailed length number of the tooth than the one on wikipedia, so it looks like they are other sources for it: carnivoraforum.com/single/?p=8240143&t=9380168rry I missread Gottfried to refer to slant height. 19.3cm is not form a published surce and refers to slant height. I have thought 18.4 cm would have been something one user here has measured. Anyway, I already took this back and theropod already corrected me.
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Post by Grey on Mar 3, 2014 21:01:43 GMT 5
This one is more rough, the others preferable. But it still exists as an approximative method.
Yes.
It does not mean he did not use Lowry formula as well as others. Lamna is a less good model I think. Though it's not that smaller than makos. But it is understandable that these three species can be used.
Many people think Megalodons did not exceed 12 m either. We discuss rethoric at length like this.
I did not post estimates for smaller pliosaurs because we were focusing on large sizes, just like in the case of Meg. The purpose was the same.
Yes we know, you had already tried this based on the poster, and Holtz reported such a figure. Average size is not the goal of the study but will be probably part of it.
The animal known from 3 specimens, is known from specimens that achieved their lives. We have only two P. funkei but we know the larger was old, hence possibly close to the maximum size of the species. Such a statement is not known in Meg which. Yet.
Kent expressed skepticism. But the bonclones jaws say otherwise. Or there is something else we lack.
Because it's been several pages you express no interest and somewhat bellitlement of Siversson estimates. That's no offense, that's what ressort. Why don't you try to contact him ?
Still not convinced. Perhaps the spacing in GW is simply potentially wider overall. Why by great luck the jaw from boneclones is necessary an exceptionnal anormal specimen ? We're all the time speaking the same thing with you, normal, not normal...
Your assumpton is wrong, their were revisions but the final size of 5.50 m is listed as accurate (without "?"). Hubbell reported that size several times in his video on YT and in Renz book. Lengths measurements are not inaccurate, some are very problematic because of the circonstances, not that one. Are we also going to have an endless discussion on this ?
Measured length was 18 feet 1/2 inch (5.50 m). Thanks to Mike Shaw, SeaWorld (pers.comm.) Taxidermied specimen was on display at SeaWorld and jaw was later acquired by Gordon Hubbell. Total weight 4,150lbs (1514 kg) (page58 "The Sea World Book Of Sharks" by Eve Bunting). Liver mass 272 kg (600 lbs, 14.46 %); heart mass 4.5 kg (10 lbs, 0.24 %); girth 3.1 m (10' 2", 56% of TL). Shark was harpooned by fisherman Weeren near West end of Catalina Island on June 13, 1976 (14.8 km from shore of Catalina Island, 27.8 km from California coast). Accoroding to Le Boeuf et al. (1982) the stomach contents were nearly digested and could not be identified. The bulk of the material suggested a large animal, probably a marine mammal. Klimley (1985, Fig. 7) reported that the stomach contents of this fish were identified as elephant seal (Mirounge angustirostris) and that the estimated mass was 680 kg. However, these data apply to a different white shark caught on 7 Sep 1975 with TL ~5 m, namely #6 in Table 1 in Le Boeuf et al (1982) for which the stomach content were identified as elephant seal and it was estimated that the elephant seal probably measured 3 m TL and weighed 450 to 680 kg. Thanks to Andrew Sprott who later located an UPI photo with caption in the Fresno Bee dated 17 June, 1976.
Yes, I referred to Siversson because we're mainly talking about him.
I want to know the spacing used by Siversson if indeed used Lowry. Otherwise, his method and material to get these sizes estimates.
Nothing says it is necessarily an outlier. What about checking Mollet data to be sure ?
Are we going to have an endless discussion for this too ? Balk said me that was from HER presentation. They are coauthors but Pimiento focuses primarily on the extinction part, Balk on the body size trend.
I've responded to the first sentence above.
A 18 m Meg is nothing extraordinary for its species, just like a 13 m P. macromerus. Period.
Regarding Balk presentation, this does not matter as the poster could be several months old at the time of the presentation.
Pimiento in the article argues that the largest (implicitly 18 m) and smallest size was all the time the same. The poster is itself outdated and filled with potential errors. I claim that I don't think this method will give results above 18 m. In a mail, Pimiento shortly said they had for now no one above 18 m.
With Shimada they are working on numerous specimens, so including large ones. 18 m as maw is somewhat conservative compared to others methods.
The poster is outdated and the largest exceeded 18 m by less than a foot. I talked about sizes approaching 19 m or more.
Except for Gottfried, we get sizes sensibly above 18 m with all the others methods.
All animals don't grow their whole life. In the case of marine reptiles they leave skeletal remains that can indicate if they died of old age. Not in the case of Megalodon in wich we have only a wide range of growth.
Yes ?
That can be very complex. That's not a random variation, there is vast size difference between these specimens that perhaps died of natural way at sizes around 10-12 m and others that died at sizes in excess of 17 m.
Old age. It is reasonnable to directly assume the Peruvian Meg died of old age or at least was near the end of its life. Its size is very large and it does not have traces of predation (what would attack this...). In the cases of the other smallers specimens, we can think they died of disease, predation by a larger Meg or others predators, but not necessary all. What I suggest is that there were vast sizes differences between the Megs populations, not only temporally but regionally too. Just like in the Ginsu shark.
Yes but most species do not show such a potential size disparity between populations. We have Megs that we can suspect they died of old age at sizes around 10-13 m, others that perhaps approach 20 m in size. That's why I'm suggesting vast genetic differences between populations, perhaps subspecies. Something that is almost impossibe to verify only by teeth I'd think.
Well, if one width is 136 mm, it isn't small either. I've failed to translate the PDF so far.
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Post by theropod on Mar 3, 2014 21:45:09 GMT 5
Holtz reported a global average that obviously included immature individuals, that is, if you understood him correctly. a figure below 10m is not realistically representing an average adult size. And what I did was merely taking the mean of the maximum sizes throughout the periods of existence. that’S not the same as the average adult size, it was for demonstrative purposes.
Not all animals are known from specimens that "achieved their lifes". Anyway, we do not know how close to their maximum size and growth those specimens are.
Or the specimen is simply unusual.
I don’t have to put up with that. I have been discussing with you about Siversson’s estimate since pages! That I don’t think a potential disagreement with a method that’s not even documented debunks one that is (him being among the coauthors!), with some pretty straightforward observations, is not the same as "belittlement". If you seriously think that I don’t want to see what you’d say about discussions between scientists.
Believe it or not, I am, and he certainly is too, quite busy. If you have already asked him there is no point in asking about the same thing.
But it is not. Some specimens have no spacing at all. The largest I found in a picture was roughly 15%, and that figure gives estimates that are everything but conservative.
That’s not exactly "luck". But look at the facts!
So? I’m sure the previous so-called measurements were listed as accurate too. You are far too certain of this lenght measurement.
For the lower bound, quite consistent with 15% based on Carcharodon. The rest very likely based on different sharks, which I for my part don’t think are a a suitable, or as good an analogy. Let’s see whether he responds to you. The data point out to it. If it isn’t, that means that other specimens are, e.g. the ones kent referred to.
What data other than the note in the specimen list are there?
How many specimens of P. macromerus are there again?
McHenry lists only two, and by your own standards the smaller is probably an immature (like the Belgian specimen). Compare;
In two C. megalodon specimens the odds of having an 18m one among them are very low. That’s well demonstrated by the several ones we have, of which none are even close to that size. In two P. macromerus specimens there is one reaching 12.7m.
Who would prepare a poster so that the data on it would be outdated since months when the research gets presented?
The writer of the article does, and that was not Pimiento but some science journalist. But specimens at exactly 18m from every period?
Most animals don’t simply stop growing at some point, but are somewhat comparable to how sharks grow. you have no means of quantifying that "old age" scenario, and the majority of marine reptiles don’t show signs of it. You asked a question, and I answered it.
I’m not talking about random variations. I am talking about natural variation between specimens of the same species, present in all animals.
I’d be surprised if any animal, save for very rare freaks, in the free nature died of old age.
Of course, that’s certainly not a surprise.
Really? The smallest mature Brown bears (largely depending on the population they are from!) are below 100kg, and the biggest can well exceed 600.
We have Megs that we can suspect they died of old age at sizes around 10-13 m, others that perhaps approach 20 m in size. That's why I'm suggesting vast genetic differences between populations, perhaps subspecies. Something that is almost impossibe to verify only by teeth I'd think.
Assuming it’s the biggest tooth (not sure of that but it seems probable, given the position in the table and the relative lenghts), we’d get 13 and 13.8m based on Hubbel’s and the yorktown dentition.
The largest measurement in a meg dentition is not the tooth width. That’s definitely tooth lenght, whether perpendicular or slant lenght I don’t know.
A width of 136cm would suggest a very large shark, likely about 16.6-17.7m.
Don’t expect to be sucessful in the future, it’s a scanned document from the later 80s. Google translate has no superpowers.
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Post by Grey on Mar 3, 2014 22:32:57 GMT 5
Your responses are interesting for some, boring for others (all that discussion about Balk poster date). I don't think I will take the time to respond to something similar. No need to continue further because I'm not agreed (and I don't appreciate how you interpret some things) we're basically agreed. Only where you're satisfied and make a day, I'm not. In any case, you'll have more tools to predict average size when the paper is released than now, if the average size itself is not mentionned. Even less in Megalodon. As if by chance. You don't know if the method used by Siversson is not documented (and as far I remember you often prefer your own methods than the ones that are properly published or perhaps I'm confusing you with another member ?). He probably used Lowry (perhaps with another) for his estimates about Meg. That is bellitlement to state his estimates are not rigorous, not interesting and that yours are valid by comparison. I believe that you're certainly busy. I've sent him mails a time ago, so it's worthwhile that another interested in how he did tries too. But you don't seem to be interested so far as you refuse to investigate this further and make a conclusion. Which largest you've found ? The only we have is the one from boneclones which needs greater than 25 %. How do you judge that results are conservative or not ? The fact is that we get a massive underestimate with the white shark from boneclones. This latest is valid and had no updates since a while. To fit your percentage, the shark would need to be more than 1 m shorter. Early estimates were about 5.9 m, now it is listed at 5.50 m with more certainty. To fit your calculation it'd need to be less than 4.50 m...Here you're entirely speculating to try to valid your interpretation. This white shark length is well measured, Mollet didn't list any doubt about the 5.50 m and Hubbell reported its size several times, even while comparinf it with others white sharks. Perhaps he'll indicate that 15 % is not the upper bound based on Carcharodon. What about verify if that shark is so much anormal using Mollet's datas ? That's extraordinary how we are unlucky with the boneclones set ! (a bit of sarcasm implied). elasmollet.org/Cc/CcMorphometrics/Morphometrics.htmlSeveral much smaller than the estimated 13 m one that might represent an old individual, just like there are much smaller Megs individuals than 18 m. Marine reptiles and sharks grow their whole life, only in marine reptiles we have remains that indicate the growth status and comparison between species (most macromerus are much smaller than the 13 m one). In Meh, we almost only have teeth lost at one given moment. The old age is possible, the three sets owners, the Belgium one, the Denmark one are not all necessary dead of something else than old age. Perhaps because it is still considered available. You can cry if you want but the fact is that Balk poster is unreliable according to herself and that Pimiento's related article say otherwise. So you give me break please. So the article, that Pimiento posted on her twitter, lies and tells hogwash. Happy ? Seriously man. Balk sent me her graph repeating "it's unreliable !" and you want to use it. One article about Pimiento works, that she herself posts on her twitter, appears, and you don't want to believe it. I favor the article informations (for now), than the poster from Balk she herself repeated me to not believe. Period. A variation between 10-12 m specimens and others 17-18 m is not a random variation. Except for dwarfism, there are no 1-1.2 m adults H. sapiens and others 1.7-1.8 m. Apex predators and very large animals can. Though dying of old age implies becoming weaker and fall prey to scavengers. Including large Megs too. Interesting but not valid comparison. Here we talk about length figures for Meg, bears know huge variations of weight of along the year without changing their size. Find another example related to length figures, not weight. My bad I thought you had written it was width. Their are logicial translating PDF but this one is protected...
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Post by creature386 on Mar 3, 2014 23:12:06 GMT 5
I have to say, since quite a while, I feel like Runic when reading these debates. I rarely respond to the longer posts (if I do, only with very short replies) and I mostly don't even understand them. From what I understand, the average size debate again begins.Why the even less? You have argued that the samples are too small in any of the known prehistoric animals for average size stuff, but how do you know then that we know less about it in Megalodon? We have quite a sample which can tell us when a specimen slowly comes close to the maximum of it's size. We know that few Megalodon's in a far larger sample than in the pliosaurs reached 18-20 m. Therefore, theropod is not far off when he says it would be far more likely to find a pliosaurus specimen significantly larger than the known than in Megalodon. This does not mean I want to compare some "average" Megalodon with the sizes of the pliosaurs (it was good to point out the smaller specimens by the way, many people overlook them and that includes me). I merely think the "even less" is quite unfounded.
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Post by Grey on Mar 3, 2014 23:26:13 GMT 5
Because Megalodon is mostly known by teeth. Teeth don't indicate how grown, how old the individual was, especially seeing the uge sizes variations in this species. It seems like that at one time or one region, an old large Meg could be 13 m (based on the sets), in others it could be 17 m.
As for the pliosaur, in P. macromerus we suspect the largest was old, as the others are much smaller. From the two P. funkei, the second is considered old, hence its large size.
This this whole comparison with Meg status, with all its complexity, that is unfounded.
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Post by creature386 on Mar 3, 2014 23:36:28 GMT 5
Thanks, now I understand you better. I have to disagree though. Without further information on the growth of the species, we can't tell the age of a "more complete" (than just known from teeth) prehistoric animal either. There is a reason why only few dinosaurs have published grow studies. My point was that the large sample of would make it less likely that the animal grew much larger than known than in pliosaurs.
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Post by Runic on Mar 3, 2014 23:37:08 GMT 5
I told everyone haha. Same stuff every time, just worded differently.
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Post by theropod on Mar 3, 2014 23:38:31 GMT 5
As far as that brings us, in hundreds and hundreds of megalodon teeth we have a much better chance of having found such a specimen.
Yes, by chance. Such things happen. You had no problem accepting that possibility when I used it to compared differences in great white and megalodon tooth poroportions, did you?
I prefer methods that I know, yes. That is not a constradiction. And can you show me the paper or website were he explains his estimates in detail?
We’re running in circles.
didn’t you read my posts back when we discussed this?
Kent writes no spacing at all, with some degree of variation. You can find pictures of jaws were the roots of adjacent teeth are in contact, others with up to 15% spacing.
And that the regression is apparently reliable, and that great white sharks don’t usually show a spacing of 24% between adjacent teeth. If you have better data, post them!
what percentage are you talking about? With 15% it’s merely 46cm! Certainly not too much of a disparity to be due to a measurement issue, unusual proportions, or both.
Where exactly did he do that, and are you sure he was not talking about another shark?
If he does, he does. But for now, we’ve got no evidence for that. well, certainly no more than we are lucky with a number of other specimens (same here)
there are no formulas given, but it would certainly not be impossible for a shark with the given weight to be 5m long rather than 5.5. Do you happen to know their catalogue numbers?
Your speculation that this one was particularly old are no better than speculations that a random megalodon was. there don’t appear to be data on it. No wonder, it’s just a huge mandible without teeth. No, but Old age remains an improbable cause of death for a wild animal. If I recall correctly it was you who forst posted it and wanted to use it, discussing it extensively.
Of course preliminary data are unreliable. Unreliable is not the same as wrong or outdated.
didn’t I just explicitely state I was not talking about random variations?
there are Adult homo sapiens 1.5-1.6m tall, and others commonly 1.9-2.0m
So being killed by scavengers is a natural cause iyo, but disease isn’t?
Being killed at some stage is a far more likely scenario than getting weaker and weaker and "fading away peacefully".
That also potentially applies to Megalodon.
How about crocodiles?
I was not aware they supply a working OCR software for Japanese on their site. I’m struggling to find one that manages to read normal latin letters from scanned files!
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Post by Grey on Mar 3, 2014 23:44:28 GMT 5
Thanks, now I understand you better. I have to disagree though. Without further information on the growth of the species, we can't tell the age of a "more complete" (than just known from teeth) prehistoric animal either. There is a reason why only few dinosaurs have published grow studies. My point was that the large sample of would make it less likely that the animal grew much larger than known than in pliosaurs. In the case of these pliosaurs, my point is still valid. The larger P. funkei and P. macromerus are suspected to be at an advanced ontogenetical stade. Pliosaurs shed their teeth too, and no isolated tooth directly suggests sizes much bigger than 12-13 m, as far as I know (a 33 cm tooth theoretically belonging to a 10 m pliosaur). Larger specimens are possible, but what Theropod suggests is that equaly-sized pliosaurs to the largest Megalodons are obvious based on this. When something is not hinted by fossils records, people try to rely on what we ignore to establish their wishful thinking.
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Post by Grey on Mar 4, 2014 0:15:52 GMT 5
Irrelevant as Megalodons lost thousands of teeth all their life. Not surprising that you not necessarily found the largest teeth. Not understood. I recall that my goal is to know how he did while asking him. I'm interested in all methods, not selectively handpicking them. Yes. But you have not verified this since we have no other example than the boneclones jaws. If you have a data of several sharks presenting 0-15 % of spacing other than the boneclones jaws, you post it. That's all I want, to verify this. With 4.2 %, around 4.50 m. That's too much as underestimate. There is a video in YT, the size he lists corresponds to the measurements from Mollet et al. There's nothing to discuss, this shark was not 4.50 m. The fact is that he lists Hubbell's specimen a bit larger than you and that you don't consider you don't have necessarily all the good data at hand. So show me others specimens confirming the spacing of 0-15 %, that's all I ask. It was not about Mollet figure but about morphometrics of upper jaws perimeter to apply to a given size. Try to find the infamous outlier (seriosuly no sarcams intended) ! elasmollet.org/Cc/CcMorphometrics/DUJP.gifNo and so what ? I'm no graduate student. Still this individual is much bigger than the others. Have the others been acknowledhed to be juveniles ? Wasn't McHenry suggesting the larger to be at an advanced age ? Just asking. When I talk about an old animal sensitive to disease or scavengers, I include this in old age. Totally wrong, I've all the time recalled this was just a primarily, not so reliable doc and never argued to extensively work on it. Just reporting what it said. You're not honest to accuse me of this when you're the one who still refers to it. The poster is filled with errors, not complete, so unreliable. Without developement behind. Less massive than the difference in Meg. And humans about 1.5 m are anything but common. Here were are talking about 4 Megs in the 9-12 m. Now some are certainly juveniles though. What did I wrote above ? I've overlooked the disease. I include this into dying of old age, old age being directly related to scavengers or disease. To anything, but we were talking about comparative length figures. That's a good example. That is certainly possible but I didn't want to spend a time to found the appropriate program for the task.
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Post by Grey on Mar 4, 2014 2:12:40 GMT 5
Theropod, about Uyeno et al. this sources states they had themselves published a method for Megalodon : One revered formula was published in 1989 by Uyeno, et al. This team calculated that the largest megatooth specimen at their university in Alberta comes from a megalodon over 48 feet long and weighing 77,092 lbs. www.fossilera.com/pages/megalodonNot sure if they have not confused this with something else, I'll verify. Edit : seems they have confused with Gottfried from that source : www.sharksteeth.com/megatoothshark.htm
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Post by coherentsheaf on Mar 4, 2014 3:44:18 GMT 5
Ok since there is much talk regarding specimen of P. macromerus. Here is the discussion in Benson et al., mentionig in total 3 animals that can be attributed to the species:
"NHMUK 39362 has previously been assigned to P. grandis (Owen, 1869), but Lydekker (1889a) indicated that there is no evidence that the syntypes of this taxon even belong to Pliosaurus. Further, there exists no overlapping material between these syntypes and NHMUK 39362 (Tarlo, 1960). OUMNH J.10454 is also referred here to P. macromerus based on its similarities in mandibular symphyseal tooth count with NHMUK 39362. The two specimens also occur at approximately the same stratigraphic level (Figure 1). However, OUMNH J.10454 has a mandibular tooth count of approximately 60, but large parts of the posterior mandible of this specimen have been reconstructed which might explain this discrepancy (pers. obs.). Two associated lower jaw fragments, OUMNH J.50376 and OUMNH J.50377, (each constituting one ramus of a lower jaw from a single individual) that are from the same pit as OUMNH J.10454 and are of similar size, are also referred to this P. macromerus. The retroarticular process in all of these specimens is Type III (Figure 6)."
So in total we have three animals, two of which are very large.
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Post by Life on Mar 4, 2014 5:08:03 GMT 5
I would like to bring more objectivity to this debate with some "qualitative" judgment which is also important for this topic.
I have noticed that too much importance have been given to "quantitative" dynamics of size estimation of Megalodon. Typical approach is to extrapolate the size of GWS to proportions of Megalodon to get an idea of the size of the latter based on the size of its fossils since GWS is regarded as the closest living analogue to Megalodon.
However, I would like to clarify that shark biology is not a mathematics-driven subject. Gottfried et al (1996) wisely presented a "size range" for a single Megalodon they considered for size estimation in their work; 15.9 - 20.3 m in TL. The most conservative figure have become a popular reference point in literature but it is not absolutely valid either just like the most liberal figure, truth could be somewhere in the middle.
Their are so many variables to consider in this debate; Megalodon and GWS are superficially similar in the context of their respective biological ground realities and it is possible that both have different TL - BL ratio based dynamics (if vertebrae are also considered in the equation).
It shall be kept in mind that various size estimation methods impose restrictions that are valid for GWS on Megalodon, therefore the figures that we get for Megalodon with this extrapolation are not absolute either (IMO, these figures represent minimum possible size(s) for each specimen of Megalodon). On top of this, fragmentary remains make this matter even more controversial.
I like Shimada's method though, it is designed to estimate the size of a shark from various aspects of its dentition and not just Anterior teeth. Their are other methods as well but it should be taken in to consideration that teeth are just one aspect to consider to estimate the size of Megalodon. It would be unwise to draw conclusions from just this approach and declare lets say 18 m figure as an outlier or something. These matters should be addressed from not just quantitative dynamics but also qualitative dynamics which are equally valid and sound at minimum.
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Post by Grey on Mar 4, 2014 5:14:51 GMT 5
Agreed Life. Theropod and I are focusing on the details of one of these methods (jaws perimeter based) and how Mike Siversson calculated it exactly.
Regarding Shimada, theropod suggests that it is prone to (relative) overestimates using posterior or lateral teeth, and underestimates with anteriors teeth, considering that Megalodons had more compact teeth at parity than the white shark. Only, I don't see how all the team of Megs experts who used that method have not considered this.
Also, Shimada highest estimates, for now, do not exceed 18m, which means that, while not overly conservative, is more modest estimates that based on the largest or widest teeth yeild in sizes approaching 20 m.
We are also discussing about the occurence of giants (+ 16 m) Megs. Theropod thinks they were exceptionnal specimens, while I think that as some populations, by time and region, had vast sizes differences, some Megs in some areas being of more modest size. It seems that what will appear of Pimiento's works.
Look at the case of Bertucci jaws. It is composed of 182 teeth. They were not associated and from the same region. While we can agree some could come from the same giant shark, this was certainly not the case of them all. Still, their respective sizes allowed to make a giant jaw. Which means, at least in that area, large Megalodons were anything but a sheer rarity.
The other situation is probably true in others places, excluding nurseries, were teeth reaching 15 cm are very rare or never occuring.
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