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Post by Grey on Apr 12, 2019 21:24:08 GMT 5
For now, none of the giant physeteroid teeth found in the world seem to indicate animals as large or larger than the Peruvian specimen except for some Chilean teeth that appear comparable.
We never know but for now I wouldnt speculate too much.
I certainly accept the ~17-18 m figure; even if the holotype was actually only 15-16 m, I can envision larger specimens.
I need stronger data to accept Livyatan growing larger than that.
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Post by elosha11 on Apr 12, 2019 21:25:10 GMT 5
Currently, size of the body and the oral cavity are the main determining factors known for this match. All in all, estimates show both to be in a similar size range, but it is definitely true that current estimates and material available suggest megalodon to have been able to grow larger with a predatory apparatus more voluminous. Or course there is only one good specimen of Livyatan and I'm perfectly open to the possibility of larger specimens but the extend and magnitude of this is unknown, even more since this only specimen of Livyatan is in a size range quite wide (14-18 m). To my knowledge, none of the isolated teeth found in various parts of the world referrable to the genus are indicating animals larger than the Peruvian specimens. There are reported 40 cm teeth (straight or along the curve?) from Chile but Lambert et al. doesn't seem to consider it evidence from a larger individuals, furthermore the Peruvian specimen upper teeth may well have approached 40 cm in length, simple scaling the diameter between the widest lower teeth and upper tooth would indicate that. Nonetheless, admitting those isolated alleged 40 cm teeth would correspond to the lower 36.2 cm teeth and using the upper estimate of 17.5 m, would suggest 19.4 m. Our study using the parameters of upper dentitions among lamniforms suggests a conservative size of 21.3 m from the big tooth in Gordon Hubbell's collection. Moreover, teeth comparable or larger or very large from more posterior positions do exist. Something often stated for many extinct taxa is true as well for O. megalodon, we probably didnt find the very largest teeth from this genus, and thus the largest possible individuals. So all in all, there are more reasons, some explained by sampling bias but not only, to consider megalodon to have been marginally the larger of the two, and quite probably the mightier. Even if this statement could very well change or not. Something else to note, Boessennecker 2019 reports killer sperm whales to go extinct before O. megalodon. So claims of superiority of macroraptorial cetaceans over O. megalodon driving it to extinction, either by competition or physical superiority, appear to be unfounded. Great to see you post Grey. I will have further comments on this thread as time allows. But thanks for the further updates on your study! |
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Post by Grey on Apr 13, 2019 4:21:38 GMT 5
You welcome elosha,
By the way, a contact just sent me the picture of a tooth all natural 147.47 mm in crown width.
Scale it from the G. Hubbell tooth, this makes 23.61 m. A little tad larger than the Meg movie female. The real megs that could really approach something as monstrous as this well made CGI shark. Something statistically and perhaps biomechanically that massive not implausible. Which, btw, would also make the possibility of sperm whales at 24-25 m real.
Yes gills are theoretically less efficient for size than lungs but cartilage is cheaper to grow large.
Recent study shows megalodon body was as hot as the one of the whales, much hoter than even the slow-feeding whale shark that grows up to at the very least 35 tonnes. The much more colder bodied filter Leedsichthys could reach at least 45 tonnes.
Let's guess what size the skeleton and body heat of a much more advanced endothermic uniquely apical shark could produce ? The largest marine predator by a small margin with Livyatan that has ever evolved on the planet.
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Post by prehistorican on Apr 13, 2019 8:00:06 GMT 5
Yes the 35-40 degrees Celsius body temperature of C. megalodon is significantly higher compared to 20-30 degrees Celsius of ancestors of great whites and makos. It would have had to have a relatively high metabolism/feeding and activity. "Their preliminary results suggested that megalodon was "quite warm" for a shark, Griffiths said. Ancestors of today's makos and great white sharks that swam alongside megalodon millions of years ago likely had body temperatures of about 68 to 86 degrees Fahrenheit (20 to 30 degrees Celsius). By comparison, megalodon may have been running a body temperature as high as 95 to 104 degrees F (35 to 40 degrees C), which is the body temperature of whales, Griffiths said. With such a high body temperature, megalodon must have had a very active metabolism that required frequent feeding, Griffiths said. Then, the climate warmed, and megalodon's prey moved to cooler waters at higher latitudes" www.livescience.com/64274-megalodon-shark-body-temperature.html |
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Post by Life on Apr 13, 2019 12:44:06 GMT 5
I wonder why paleontologists do not look into the possibility of Megalodon eating each other to extinction when 'Pliocene epoch conditions' restricted 'roaming spaces' for this species worldwide. This study is close: adsabs.harvard.edu/abs/2018AGUFMPP13F1405NCompetition theory never clicked to me. |
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Post by theropod on Apr 13, 2019 13:09:17 GMT 5
I wonder why paleontologists do not look into the possibility of Megalodon eating each other to extinction when 'Pliocene epoch conditions' restricted 'roaming spaces' for this species worldwide. This study is close: adsabs.harvard.edu/abs/2018AGUFMPP13F1405NCompetition theory never clicked to me. Probably because animals of one species don't "eat each other to extinction", when carrying capacity is reached, population declines, but only until below carrying capacity. As long as there are resources for some of the species, this does not lead to extinction. If what you mean is that it ate its prey into extinction completely, which would have permanently removed the resource it subsisted on, that is also unlikely, since that prey successfully existed alongside it for millions of years. Also many whales survive to this day that would potentially be suitable prey, and many survived that were preyed upon back then. So it seems unlikely Megalodon could have been the causative factor in its own extinction. I think a general drop in ocean productivity in warm water coupled with the evolution of migratory patterns to polar regions in whales (making many previous prey items at least seasonally unavailable) is a likely factor, as is competition for remaining prey (like pinnipeds) from smaller predators more suitable to these conditions. |
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Post by Life on Apr 13, 2019 14:45:37 GMT 5
I wonder why paleontologists do not look into the possibility of Megalodon eating each other to extinction when 'Pliocene epoch conditions' restricted 'roaming spaces' for this species worldwide. This study is close: adsabs.harvard.edu/abs/2018AGUFMPP13F1405NCompetition theory never clicked to me. Probably because animals of one species don't "eat each other to extinction", when carrying capacity is reached, population declines, but only until below carrying capacity. As long as there are resources for some of the species, this does not lead to extinction. If what you mean is that it ate its prey into extinction completely, which would have permanently removed the resource it subsisted on, that is also unlikely, since that prey successfully existed alongside it for millions of years. Also many whales survive to this day that would potentially be suitable prey, and many survived that were preyed upon back then. So it seems unlikely Megalodon could have been the causative factor in its own extinction. I think a general drop in ocean productivity in warm water coupled with the evolution of migratory patterns to polar regions in whales (making many previous prey items at least seasonally unavailable) is a likely factor, as is competition for remaining prey (like pinnipeds) from smaller predators more suitable to these conditions. Chances of Megalodon attacking each other might be LOW throughout the ages because even a juvenile Megalodon is a high-risk potential prey, and a species wants to perpetuate, but large sharks are known to take their chances with smaller sharks in the wild. I am alluding to the 'Pliocene conditions' which somehow restricted Megalodon's roaming spaces across the globe besides a significant drop in marine biodiversity and whales being able to subsist in polar regions.  Some researchers have noted that Megalodon had marked some biodiversity-rich geographical shallow-water spots as 'nursery areas' where its young (neonates and juveniles) would be relatively safe from predation, learn, and grow. Recall this study for instance: journals.plos.org/plosone/article?id=10.1371/journal.pone.0010552"More recent studies have defined nursery areas as geographically discrete essential zones for shark survival [3] that provides them with two types of benefits: protection from predation (mainly larger sharks [2]) and abundant food resources. Productive, shallow-water ecosystems thus provide sharks significant protection from larger predators and/or abundant food resources, both of which are essential to survival [4]."This dynamic might not have lasted in Pliocene, and adult Megalodon might have gone after juvenile Megalodon on a frequent basis during this period. Think about the dietary requirements of adult Megalodon in general and what were they supposed to do in periods when whales were nowhere in sight. Cannibalistic tendencies might be the FINAL NAIL in the coffin for this species during trying times all along. This make sense to me - the missing piece in the puzzle. --- As for relatively small predators providing competition to Megalodon in any zone? Give me a break. I can easily visualize even juvenile Megalodon giving the Great whites and other sharks a run for their money in potential encounters. Refer to you following studies:- - Purdy, R. (1996) Paleoecology of fossil White Sharks. In: Kimley, A.P. and Ainley, D.G., Eds., Great White Sharks: The Biology of Carcharodon carcharias, Academic Press, San Diego, 67-78. dx.doi.org/10.1016/B978-012415031-7/50009-4
- Diedrich, C. G. (2013). Evolution of white and megatooth sharks, and evidence for early predation on seals, sirenians, and whales. Natural Science, 5(11), 1203.
--- Many whales did not just survive to this day, but marine biodiversity RESURGED during the Pliestocene epoch in the absence of Megalodon. A large number of species vanished during the 'Late Miocene - Middle Pliestocene' period, and even Killer Whales were on the brink of extinction at some point in the Pliestocene but REBOUNCED eventually. Gigantism among whales is also a recent evolutionary process. |
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Post by theropod on Apr 13, 2019 16:09:58 GMT 5
This dynamic might not have lasted in Pliocene, and adult Megalodon might have gone after juvenile Megalodon on a frequent basis during this period. Think about the dietary requirements of adult Megalodon in general and what were they supposed to do in periods when whales were nowhere in sight. Cannibalistic tendencies might be the FINAL NAIL in the coffin for this species during trying times all along. This make sense to me - the missing piece in the puzzle. Of course animals might resort to cannibalism in times of scarcity or to use available resources more efficiently. Usually this is an adaption that INCREASES fitness, not decreases it. But if C. megalodon resorted to cannibalism because other prey was unavailable, then it was not cannibalism that drove it into extinction, it was lack of other prey. With no prey available except for conspecifics, it would have gone extinct with or without cannibalism. So "eating each other to extinction" was not a causative factor of its extinction, and that is the answer to your question. Please note the difference between the ecological concepts of "competition" and "predation". |
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Post by Grey on Apr 13, 2019 19:20:40 GMT 5
Regarding the very wide tooth I alluded, I
forgot to recall it is most likely a lateral one, which would correspond in size, compared to the complete sets, to something similar to the G. Hubbell tooth, 21 m plus, anyhow already in the Meg movie size range ...
Btw, the new up to date life size model for the Smithsonian supervised by Bretton Kent and Hans Sues will be mounted at the end of the month at the Smithsonian. It is 15 m long, which is the max size the hall where it will throne could contain.
Interestingly its dentition is a cast of the Bone Valley dentition from which we extrapolated 11-12 m TL estimates but which seems to work also in a 15 m model.
It will be more mako-like in shape.
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Post by elosha11 on Apr 13, 2019 23:11:39 GMT 5
You welcome elosha, By the way, a contact just sent me the picture of a tooth all natural 147.47 mm in crown width. Scale it from the G. Hubbell tooth, this makes 23.61 m. A little tad larger than the Meg movie female. The real megs that could really approach something as monstrous as this well made CGI shark. Something statistically and perhaps biomechanically that massive not implausible. Which, btw, would also make the possibility of sperm whales at 24-25 m real. Yes gills are theoretically less efficient for size than lungs but cartilage is cheaper to grow large. Recent study shows megalodon body was as hot as the one of the whales, much hoter than even the slow-feeding whale shark that grows up to at the very least 35 tonnes. The much more colder bodied filter Leedsichthys could reach at least 45 tonnes. Let's guess what size the skeleton and body heat of a much more advanced endothermic uniquely apical shark could produce ? The largest marine predator by a small margin with Livyatan that has ever evolved on the planet. Would you be permitted to post the picture of that tooth? Perhaps in the Megalodon size thread where we have many other such large teeth? |
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Post by sam1 on Apr 14, 2019 2:37:21 GMT 5
Aren't you guys putting too much face value assumptions into those single isolated teeth?
You need to keep in mind that there are no two individual equally large specimens - sharks being among the most notable examples, due to their sheer number of teeth - of the same species that have exactly the same jaw and individual teeth proportions.
The differences are rich and profound between individuals. I was just browsing through some white shark jaw galleries and their shapes and teeth proportions vary wildly, and there are often some outlier teeth within the jaw. I'd bet many smaller individuals can be found with a tooth or two that is bigger than the biggest teeth from some larger individual of the species. Not as a rule, and not typically of course, but I hope you get the point.
Seems like tere's just way too many speculative conclusions here.
I'd be interested to know what's the largest GWS tooth ever found?
And how big were the biggest teeth of the largest verified specimens.
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Post by Grey on Apr 14, 2019 16:26:33 GMT 5
This method relies on dentition size mainly, tooth size is indirect in the equation here. The biggest isolated teeth are only used as templates here within the dentition. Of course this is all theoretical and those figures are the mean of the range of size.
Basically, we found out that the Aurora upper dentition has the summed width that would correspond, in a GWS, to a body between 15 and 18 m, with a mean 16.5 m, very much like the skull width of Livyatan would correspond to a 16-17.5 m Zygophyseter or to a 14-16 m Physeter.
These big isolated meg teeth are much larger in all dimensions than their counterpart in the Aurora dentition and suggest in various cases a GWS-based TL of at least 21 m. It is notable that using GWS is the most conservative approach, similar data from makos suggest a 18-20 m range for the Aurora dentition.
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Post by theropod on May 1, 2019 23:03:46 GMT 5
I’m going to review a few popular reconstructions based on best-fit scaling of the 3D model I posted on the profile thread to the respective images scaled to 16.8m total length. first off, Gottfried et al.’s reconstruction: I’m getting about 65t. Pretty good considering this was in 1996, and they didn’t have a volumetric reconstruction. Certainly still within a realistic range for a modern great white, although it certainly is in the upper range.
This one I modified the model for to match the given dorsal silhouette, and it turns out at a surprisingly mild 61t. However the tail is way narrower than it would be even in a great white, and at the same time way deeper. All in all, this one isn’t so much too bulky, but rather just badly proportioned.
Depends on which reconstruction you are using, either one from the internet or ones with credibility and assuming the shark isn't completely a scaled up porbeagle/white shark . BK Kent's reconstruction seems to be one with credibility as show by Grey in the recent TV doc, that was a BK Kent shaped C. megalodon. This is a photorealistic version:  This "credible" reconstruction would mass 90 tons at 16.8m (formula average would be 52t, maximum 57t). Not impossible, I’m sure you can find great whites somewhere that have those kinds of proportions, but certainly freakish. This one’s about the same. This one is plain ridiculous, 109 tons. Partly because this one has a very small caudal fin, which decreases the total length relative to body size (but it would obviously be way too massive even with a corrected fin). |
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Post by Grey on May 3, 2019 19:23:14 GMT 5
Nice work. Wait for the life size "most up to date" megalodon model at the Smithsonian supervised by Brett Kent and Hans Sues to test it although it will be maybe trickier because it is reportedly in a turning around pose.
Apparently it is 15.2 m/50 ft long, 12.5 ft in maximum body depth (said by Kent in a radio talk), 22 ft fin to fin, about 10 ft (?) in jaws/head width (according to Hans Sues).
It is allegedly more athletic than Gottfried's model but these measurements still represent a surprisingly very massive creature.
The basis for it is the third "credible" reconstruction but they modified it again. It is reportedly being mounted at this moment.
A volumetric estimate with it would be very cool.
I usually tend to think anything is freakish regarding megalodon body mass estimates. The species in itself is a freak as no other carnivorous fish has ever approached these reported proportions.
I tend to stay on the 50 tonnes mark for meg while still open to the higher figures.
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Post by theropod on May 3, 2019 22:33:40 GMT 5
A turning pose wouldn’t be a problem, though I suppose good photographs without too much fish-eye effect of a model that big would be hard to come by, not to mention a top view. But I’m sure I can at least do an approximation of someone comes up with a few photographs.
What I referred to as freakish is how much more robust than a typical representative of the species (which would most likely be somewhere in between the mean model and the Gottfried et al. model I produced) that specific one would be (90t at 16.8m is the equivalent of a 6m great white shark weighing 4t), as of the best of our knowledge. Around 50t (or slightly above that) is indeed the best estimate for a shark the length you are proposing. What is usually meant by "freak" is something totally out of the normal range of its species, such as a 1t polar bear, or a great white massing 4t at 6m.
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