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Post by prehistorican on Aug 5, 2018 4:32:23 GMT 5
Well it seems to be obviously fantasy. But this is quite close to a Megalodons maximum size. On the Wikipedia page there are only up to a 24-26m sperm whale, and the head gets proportionately bigger in bulls with age (20-25%). "The sperm whale is the largest toothed whale, with adult males measuring up to 20.5 metres (67 ft) long and weighing up to 57,000 kilograms (56 long tons; 63 short tons).[32][33] By contrast, the second largest toothed whale (Baird's Beaked Whale) measures 12.8 metres (42 ft) and weighs up to 15 short tons (14,000 kg).[34] The Nantucket Whaling Museum has a 5.5 metres (18 ft)-long jawbone. The museum claims that this individual was 24 metres (80 ft) long; the whale that sank the Essex (one of the incidents behind Moby-Dick) was claimed to be 26 metres (85 ft). A similar size is reported from a jawbone from the British Natural History Museum. A 20m specimen is reported from a Soviet whaling fleet near the Kuril Islands in 1950.[35][36] There is disagreement on the claims of adult males approaching or exceeding 24 metres (80 ft) in length." 30m?!?  That's 6 meters over the McClain reported maximum. Yeah those damn biased fanboys. Sorry to rain on your parade, but 30m is exceeding blue whale mass buddy. |
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Post by Grey on Aug 5, 2018 5:53:53 GMT 5
^No. Actually it's a lot higher because it's not just the "obscure whalers" measurments but the actual evidence to support them. The funny thing is, we have a whole fricking jawbone of this extant species that can extrapolate based on the actual skeletons of the creature to anywhere from 24-28m, even 30m. But no, a single fossilised tooth from a largely mysterious species extinct from millions of years ago is a more telling data. T.L.D.R., fanboys and their biased logic. Sorry for raining on your parade. Hope the movie is good, but for sake of sanity, don't take it as anything more than pure fantasy. There are no jawbones supporting anything like this. The Nantucket jawbone, becausecof the strong allometry in sperm whale skulls, indicates a 21 m individual rather than a 24 m one. But I don't deny something like 24 m based on MCClain 2015. 23 m is statistically plausible for a meg using the most solid size parameter available. G. Hubbell big tooth is not even the largest/widest on record. I wait for the measurements of another dentition to confirm that. This is not based on a single tooth but on various massive teeth and on dentition morphometrics, assuming meg had a lamnid-like dentition/body length ratio. We're all in the realm of theories here, no need to call people fanboys and frankly I'm not certain you're the most objective guy around dude even if you have improved quite a bit since years. 75 ft is simply based on the unprecise but not necessarily wrong 1 inch tooth = 10 feet rule of thumb. That's all. The Bertucci composite dentition would fit nicely in a 75 ft great white-like body, that's all. The meg in this movie is far less problematic than the JW Mosasaurus. |
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Post by Grey on Aug 5, 2018 5:55:56 GMT 5
The error bars on size estimates based on single teeth are just as high as those on obscure whalers’ measurements, are they not? Honestly, I far more trust maths based on actual material than tales 100 years old from whalers. No sperm whales experts or scientific records take those claims seriously. Not saying that any meg specialist would take seriously the upper estimates based on Shimada either, but the data based on dentition morphometrics is not widely available yet. The point is, unlike the JW Mosasaurus, the movie Meg is, within the statistics, plausible. That's not to say it is an absolute probability. I'd wait for more data from the dentitions for this. |
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Post by theropod on Aug 5, 2018 7:03:50 GMT 5
Grey : Even if whaler records were routinely inaccurate by several meters, by comparison that's not actually looking too bad. I think you demonstrated that nicely yourself. Look at the range you got for the complete dentition, 15-21m: that is not small to begin with (what are the the SDs for your estimates btw?). Now add the additional variation of a single tooth within that dentition (it would be interesting to quantify that, since you have all the data necessary to do so). And then, of course, the real uncertainty is even greater due to comparing different species. Of course, with some of these whales there is the problem that there is no definite proof that they really existed (though I think we can rather favourably compare that situation to there being no proof that meg was proportioned like a great white), but thee question is, what motivation would there be for whalers to make it up alltogether? McClain et al. 2015 did take 24m sperm whales seriously. Carrier et al. 2002 claimed the whale that sank the Essex was 26m long…likely not more than a guess by the sailors, but this does constitute such a size being "taken seriously". sam1 : I think your size estimates for the Nantucket jawbone are way too liberal. Even so, that specimen is probably the biggest reliably reported (as in, at least there is a verifiably measurable specimen) sperm whale.  I used the average ratio between the two reported skull and mandible lengths from James & Soundararajan to calculate the mandible lengths for Lambert et al.’s dataset of male sperm whales with known TL, then ran a linear regression (the residuals are not statistically significantly correlated with size, at R²=0.12 and p=0.27) of TL against mandible length. I’ve attached my data if someone wants to check my numbers. The 75% prediction interval would be 20.0-23.4m, for 50% it is 20.8-22.7m. So 21m is a bit on the conservative side, but over 25m is extremely unlikely. Considering this, I do think the 24m bull cited by McClain et al. is plausible though (at least it is within the 95% PI for the Nantucket jawbone. Carrier, D. R., S. M. Deban, and J. Otterstrom. 2002: The face that sank the Essex: potential function of the spermaceti organ in aggression. Journal of Experimental Biology 205:1755–1763.
James, P., and R. Soundararajan. 1981: An osteological study on the sperm whale Physeter macrocephalus Linnaeus from Indian Ocean. Indian Journal of Fisheries 28:217–232.
Lambert, O., G. Bianucci, K. Post, C. de Muizon, R. Salas-Gismondi, M. Urbina, and J. Reumer. 2010: The giant bite of a new raptorial sperm whale from the Miocene epoch of Peru. Nature 466:105.
McClain, C. R., M. A. Balk, M. C. Benfield, T. A. Branch, C. Chen, J. Cosgrove, A. D. Dove, L. C. Gaskins, R. R. Helm, and F. G. Hochberg. 2015: Sizing ocean giants: patterns of intraspecific size variation in marine megafauna. PeerJ 3:e715.
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Post by sam1 on Aug 5, 2018 11:08:11 GMT 5
Theropod, I think the main factor here is the sample size. Two skulls are just not enough.
The total proportional range in sperm whales is pretty big. The head length/total length proportions can go from 1:3 to 1:4, and the skull length/head length can vary significantly too, depending on the rostrum tissue(it tends to be bigger the bigger the animal is).
A 5.5m jawbone means a head of around 7m length, so the possible TL could be 21-28m.
But I won't hijack this thread any more.
We can discuss the maximum possible size from a 5.5m mandible in a separate one.
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Post by Grey on Aug 6, 2018 6:13:10 GMT 5
Grey : Even if whaler records were routinely inaccurate by several meters, by comparison that's not actually looking too bad. I think you demonstrated that nicely yourself. Look at the range you got for the complete dentition, 15-21m: that is not small to begin with (what are the the SDs for your estimates btw?). Now add the additional variation of a single tooth within that dentition (it would be interesting to quantify that, since you have all the data necessary to do so). And then, of course, the real uncertainty is even greater due to comparing different species. Of course, with some of these whales there is the problem that there is no definite proof that they really existed (though I think we can rather favourably compare that situation to there being no proof that meg was proportioned like a great white), but thee question is, what motivation would there be for whalers to make it up alltogether? McClain et al. 2015 did take 24m sperm whales seriously. Carrier et al. 2002 claimed the whale that sank the Essex was 26m long…likely not more than a guess by the sailors, but this does constitute such a size being "taken seriously". sam1 : I think your size estimates for the Nantucket jawbone are way too liberal. Even so, that specimen is probably the biggest reliably reported (as in, at least there is a verifiably measurable specimen) sperm whale. I used the average ratio between the two reported skull and mandible lengths from James & Soundararajan to calculate the mandible lengths for Lambert et al.’s dataset of male sperm whales with known TL, then ran a linear regression (the residuals are not statistically significantly correlated with size, at R²=0.12 and p=0.27) of TL against mandible length. I’ve attached my data if someone wants to check my numbers. The 75% prediction interval would be 20.0-23.4m, for 50% it is 20.8-22.7m. So 21m is a bit on the conservative side, but over 25m is extremely unlikely. Considering this, I do think the 24m bull cited by McClain et al. is plausible though (at least it is within the 95% PI for the Nantucket jawbone. Carrier, D. R., S. M. Deban, and J. Otterstrom. 2002: The face that sank the Essex: potential function of the spermaceti organ in aggression. Journal of Experimental Biology 205:1755–1763.
James, P., and R. Soundararajan. 1981: An osteological study on the sperm whale Physeter macrocephalus Linnaeus from Indian Ocean. Indian Journal of Fisheries 28:217–232.
Lambert, O., G. Bianucci, K. Post, C. de Muizon, R. Salas-Gismondi, M. Urbina, and J. Reumer. 2010: The giant bite of a new raptorial sperm whale from the Miocene epoch of Peru. Nature 466:105.
McClain, C. R., M. A. Balk, M. C. Benfield, T. A. Branch, C. Chen, J. Cosgrove, A. D. Dove, L. C. Gaskins, R. R. Helm, and F. G. Hochberg. 2015: Sizing ocean giants: patterns of intraspecific size variation in marine megafauna. PeerJ 3:e715. It is true the margin is wide, of course it is the widest possible range, including all ontogenic stages and outliers. Excluding those, the range is reduced at 17-20 m, far smaller, but still suggesting, using G. Hubbell tooth crown width of (reportedly) 134 mm, a range of 21-24.7 m. G. Hubbell is the most known of the giants meg teeth in private collections, but do note I have found strong indications of even larger ones, some very large potential posteriors and some huge fragments. So this is not an absolute max size range going by this method. You're absolutely true when you write there is also the variation of the teeth themselves, within the dentition. A larger dentition could very well had smaller upper anteriors but larger lateral and posteriors making the dentition longer. This is why I wait for more data from another larger dentition and insist on the very theoretical view of this. However, I can say that, compared with the Yorktown set, it appears the Bertucci composite recreation is reasonable. I briefly discussed this with S. Godfrey and Brett Kent, and they consider it plausible. Only Shimada criticized it but this was apparently based on his previous observation of the Bone Valley dentition, belonging to a smaller individual with a slightly faster decreasing size of its teeth, and on GWS dentition. But at least based on the adult set, Bertucci's proportions are solid. The man actually built it with the help of G. Hubbell and Cliff Jeremiah. Thus, this composite dentition, if not confirmed beyond any question, does suggest a truly huge individual. Yes, that meg had GWS proportions is not exactly established, but the elements we have from it (larger dentition at the same upper anterior size, higher number of vertebra, strong similarities in the centra) do suggest this. Note, that using makos dentitions result in larger sizes estimates than with GWS specimens. Like I proposed earlier, favoring any smaller size figure for meg, like an absolute max size of 18 m, would strongly imply an extremely wide jawed shark, and quite likely a body plan even bulkier than proposed by some authors. Regarding the sperm whale case, I don't deny McClain 2015 although, as expressed in the Top Dog thread, there are justifiable doubts regarding the reliability of the methods used by the whalers, as well as it is strange that Gerald Wood never found such an account. Carrier 2002 simply relied on the whalers accounts. Hal Whitehead expressed doubts about this in the book "In the Heart of the Sea" as well as Richard Ellis in "The Great Sperm Whale". Very interesting graph btw, but does it include the strong allometry in the sperm whale skull ? Zenitani and Kato (2013) determined that in males, the proportion of skull length to body length increased with growth from 26% (body length, 10 m) to 32% (body length, over 16 m, most of which were considered as physically mature). They found that a 17.6 m male had a skull length of 6.89 m or 39.2 % its body length. Assuming the mandible growth is similar to the whole skull's, it throws some great doubts about the 24 m prediction for the Nantucket jawbone. McCormick had reached a similar conclusion by other means on his blog. The very point is not to say that 23 m is scientifically established yet for meg, like 18 m, but that very much lies in the realm of the statistical possibilities. Unlike the whale-sized, twice too large JW Mosasaurus. And I find the design of the shark, not a a super-size GWS but still very lamniform, very neat. |
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Post by theropod on Aug 6, 2018 18:04:02 GMT 5
I want to make clear that I have nothing against the depiction in the meg movie or its size.
The additional gill slits are a little odd (as 5 is so universal among lamniforms and 8 is higher than both the ancestral number of branchial arches and the highest number in any extant shark), but visually they work, as does the rest of the model. Oversizing it a little is hardly surprising, but this is a mild case considering the genre (looking at you Jurassic World mosasaur).
Now, I don’t have very high expectations, but that is because I don’t really like monster-movies based on real world animals in general (because most of them are garbage in terms of scripting, characters and acting, but there might be something about the premise itself that puts me off too). But certainly this megalodon is a more promising movie monster than many (giant snakes? giant crocodiles? the JP mosasaur? take your pick).
Regarding the sperm whale, I responded in the appropriate thread. An interesting question derived from that though; did you check for allometry in the crown width data?
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Post by Grey on Aug 6, 2018 20:19:05 GMT 5
Yes, finding any allometric growth is one of the subject I've focused on but it doesn't seem to occure anything significant so far although nothing is conclusive at this point.
In fact, I've come to wonder, given their extreme size and their active predatory lifestyle, if the otodontids could have evolved additional gill slits in order to get enough oxygen to operate efficiently ? Pretty much impossible to demonstrate but it would be interesting to ponder about that.
The evolution of sharks never came close to something predaceous as large as the members of this lineage, even the smallest member could grow potentially to 10 m.
According to an interview of Industrial Light and Magic, the JW mosasaur size was originally planed to be more realistic but they upscaled it because it needed to be able to grab and appear bigger than the Indominus rex at the end.
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Post by theropod on Aug 6, 2018 20:56:59 GMT 5
My initial thought about the gill slits was "unlikely", but then I have come to consider it more seriously when discussing with sam1 regarding the respiratory efficacy in large sharks. It is true that a large shark might be expected to increase gill surface area by some means.
The questions are, would a shark have the developmental pathways to evolve not one or two, but 3 additional gill arches (something not seen in any extant shark), and would it be necessary to add additional gill arches, or could the surface area be increased by some other means. I do tend to think that portraying C. megalodon with additional gill arches might be a good idea, though 6 or 7 gill slits (numbers found in extant sharks) seem more parsimonious at this point.
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Post by prehistorican on Aug 6, 2018 21:14:35 GMT 5
theropod:
It may have had larger/taller gills, a more total number of gills, more gill filaments per gill (meaning you don't neccesarily need more gills). More likely it may have even been some sort of combination of the first three. That is my opinion on the additional gill discussion for the moment. Though a large percentage of the sharks muscles should be white muscle with stored energy and such for anaerobic processes for burst speed, should it not?
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Post by theropod on Aug 7, 2018 20:44:20 GMT 5
I see no reason why meg would have a greater percentage of glycolytic muscle than great whites. Rather the opposite, since it would still have to swim constantly (and likely do so at a higher speed), which would be more exhausting at its large size. Even if its muscles were to need less oxygen, the rest of its body still needs it, and still scales at a higher power than gill area. So presumably flow through the gills, gill area, or both would need to be higher to compensate.
Do you have any detailed data on how much white muscle sharks actually have though?
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Post by prehistorican on Aug 7, 2018 23:59:31 GMT 5
theropod: I don't think I can find a study ATM. But on elasmoresearch states over 90% for general sharks (not a surprise when you look at pictures and cross sections). www.elasmo-research.org/education/white_shark/muscles_jaw.htm Not that related but apparently larger tuna have proportionately less red muscle? |
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Post by sam1 on Aug 10, 2018 0:29:52 GMT 5
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Post by Grey on Aug 10, 2018 3:50:57 GMT 5
Read it earlier. I know Hans, he's building a new meg model with Brett Kent at the Smithsonian, about 15 m long (lacking space to make it larger). Hans is not aware of the metrics suggesting size way above 18 m, actually I've just showed him the data this week. |
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Post by Life on Aug 11, 2018 17:17:18 GMT 5
Saw the movie today. Sharks look realistic in terms of appearance, strength, speed and maneuverability, and not exaggerated in terms of size either. However, this movie portray them as monsters hellbent on taking revenge which is unlikely. I find the movie disappointing on the whole; it feature some excellent action sequences but it had so much potential to offer JAWS-like suspense and horror; the director blew it unfortunately. Some experts give little thought to the psychological effect of a huge macropredator on other lifeforms. Megalodon, in the light of its biomechanics, is not only incredibly strong but it is expected to chase other beings from their kills, and it would be rare for any species to hold its ground. Livyatan Melvillei was large and powerful enough to put up a fight but it wasn't widespread and it couldn't dethrone Megalodon even in Peru. I do not think that a pod of Killer Whales would risk a confrontation with an adult Megalodon because they are smart enough to figure out that this effort might not be worth the cost. My response in Quora: www.quora.com/Who-would-win-a-Megalodon-shark-or-a-Killer-Whale-PodIMHO, climatic shifts coupled with major extinction event in the Pliocene set the course for extinction of Megalodon. With increasingly dwindling prey options, Megalodons might have turned on each other (adults eating the smaller ones). |
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That's 6 meters over the McClain reported maximum. Yeah those damn biased fanboys. Sorry to rain on your parade, but 30m is exceeding blue whale mass buddy.
