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Post by elosha11 on Sept 7, 2018 9:55:26 GMT 5
Grey, did you have any thoughts on how large Heim's whale was? It seems like it would be pretty difficult based on this one rib fragment. Thanks for the Kent interview, that was very interesting. A little surprising that he states max size as 50-55 feet; I thought in the past he'd joined with the more consensus view of around 18 meters. I guess 50-55 feet is still a safely conservative max size, but Pimiento, Ciempaglio. Silversson, Godfrey, Ehret, Ward, Gottfried, Leder and others have all provided estimates of 18 or more meters for max size. I thought Kent fell right in line with the others.
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Post by Grey on Sept 7, 2018 12:44:16 GMT 5
No idea at all, the error bar might be huge. A wild guess would be, looking at the thickness, 7-12 m ?
He usually agrees for the 60 ft mark, Ehret too sometimes uses 55 ft instead of 60 ft.
I can understand why, this is a pretty much safe mark already hard to understand how such a predatory shark, or macropredatory organism at all, could evolve that large.
It is true the metrics using teeth and even more with dentitions suggest theoretical figures easily over 60 ft when adjusted for the really big teeth but, at the same time, since there are no filter-feeding sharks that seem to have evolved larger, as they have a life style more easily allowing to grow huge, I perfectly understand Kent's caution.
The alternative is that if the largest megs were 55-60 ft long, it seems like their dentition would have been huge then, correspinding in proportions to a theoretical 65-75 ft great white.
Hard to know if such a shark would maintain an efficient body plan.
Another issue is that the gill system is less efficient than lungs to grow large. I really hope Ferrón would test this on meg in a similar manner he tested it for Leedsichthys, for which, based on his metabolism (endothermic), he predicted a maximum realistic body weight of 45 tonnes.
Either meg was really limited by these constraints at lower maximum sizes or it may have developped anatomical novelties allowing it to grow as large as some of the material mzy indicate.
Actually, even if the max was only 50-55 ft, it may have had unique traits, since there is no predatory shark today even approaching such sizes. The question is, would they allow it to grow even huge and at which extend ?
And even as odd as it seems, I wonder if the meg movie isn't throwing a hint with those additional gills. After all, six-gilled sharks today live in less rich in food sources and oxygen environment and still grow to sizes comparable to great whites, perhaps even larger.
Maybe otodontids had more gills and other adaptations allowing them them to be active hunters > 30 ft long ? Added to a marine environment filled with much more food sourced than today, it made megalodon reaching 60 ft possible and perhaps more ?
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Post by Life on Sept 15, 2018 0:47:34 GMT 5
No idea at all, the error bar might be huge. A wild guess would be, looking at the thickness, 7-12 m ? He usually agrees for the 60 ft mark, Ehret too sometimes uses 55 ft instead of 60 ft. I can understand why, this is a pretty much safe mark already hard to understand how such a predatory shark, or macropredatory organism at all, could evolve that large. It is true the metrics using teeth and even more with dentitions suggest theoretical figures easily over 60 ft when adjusted for the really big teeth but, at the same time, since there are no filter-feeding sharks that seem to have evolved larger, as they have a life style more easily allowing to grow huge, I perfectly understand Kent's caution. The alternative is that if the largest megs were 55-60 ft long, it seems like their dentition would have been huge then, correspinding in proportions to a theoretical 65-75 ft great white. Hard to know if such a shark would maintain an efficient body plan. Another issue is that the gill system is less efficient than lungs to grow large. I really hope Ferrón would test this on meg in a similar manner he tested it for Leedsichthys, for which, based on his metabolism (endothermic), he predicted a maximum realistic body weight of 45 tonnes. Either meg was really limited by these constraints at lower maximum sizes or it may have developped anatomical novelties allowing it to grow as large as some of the material mzy indicate. Actually, even if the max was only 50-55 ft, it may have had unique traits, since there is no predatory shark today even approaching such sizes. The question is, would they allow it to grow even huge and at which extend ? And even as odd as it seems, I wonder if the meg movie isn't throwing a hint with those additional gills. After all, six-gilled sharks today live in less rich in food sources and oxygen environment and still grow to sizes comparable to great whites, perhaps even larger. Maybe otodontids had more gills and other adaptations allowing them them to be active hunters > 30 ft long ? Added to a marine environment filled with much more food sourced than today, it made megalodon reaching 60 ft possible and perhaps more ? This paper might provide some answers: journals.plos.org/plosone/article?id=10.1371/journal.pone.0185185
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Post by elosha11 on Oct 1, 2018 18:10:33 GMT 5
Looks like two bitten (severed) cetacean vertebrae. From the Aurora Fossil Museum. I am also going to start posting screenshots of the pics I post, since the websites often disappear and the images are then lost. The image is attached in a Word document at the end of this post. Meg Bitten Bones.docx (130.42 KB)
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Post by elosha11 on Oct 12, 2018 21:59:55 GMT 5
New research from Stephen Godfrey and others regarding Megalodon or C. Chubutensis predatory interactions with 3.5 to 4 meter dolphins. The author believes these vertebrae got stuck between the jaws of one of these sharks while it was disabling the dolphin and demonstrates this with a set of man-made jaws that would have come from an 11 meter shark. There's a fairly wide body of evidence, certainly including this thread, showing mega-toothed feeding on cetaceans ranging from 20 feet up to 40 or greater feet. But we have increasing evidence that subadults and perhaps even adult sharks also preyed on smaller prey such as dolphins, small ceteaceans and seals. There is really nothing surprising about this, as the shark would have been highly opportunistic and would probably need to eat fairly often for a shark (not to same degree as predatory whales). I think this may also hint at the level of explosiveness and maneuverability for a shark that would far exceed a great white in size to catch something as fast and maneuverable as dolphins. Here's the article link and attached pictures. www.app.pan.pl/archive/published/app63/app004952018.pdf
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Post by prehistorican on Oct 13, 2018 2:30:07 GMT 5
3.5-4m? I reckon large bottlenose dolphins are about that big, and they are quite athletic. So I believe the shark must have been at least reasonably explosive as well to catch one.
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Post by elosha11 on Oct 15, 2018 18:15:22 GMT 5
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Post by elosha11 on Oct 20, 2018 3:01:36 GMT 5
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Post by elosha11 on Oct 26, 2018 5:10:23 GMT 5
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Post by prehistorican on Nov 2, 2018 1:33:30 GMT 5
Nice find Elosha! I wonder how big of a whale those ribs must have come from. Interesting how the great white uses more of a bleed out method and lets its prey get weakened while the C. Megalodon seems more brutal and attacks the chest cavity region or disables the prey by biting off the tail. Especially from a bottlenose sized dolphin as shown before, it must be somewhat hard to target that region specifically.
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Post by elosha11 on Nov 5, 2018 9:06:15 GMT 5
Nice find Elosha! I wonder how big of a whale those ribs must have come from. Interesting how the great white uses more of a bleed out method and lets its prey get weakened while the C. Megalodon seems more brutal and attacks the chest cavity region or disables the prey by biting off the tail. Especially from a bottlenose sized dolphin as shown before, it must be somewhat hard to target that region specifically. Thanks. Just to be clear, I think these ribs all come from different whales, which just all happened to be found in the Gulf of Mexico. Yes, Megalodon and probably the other mega-toothed sharks were definitely less picky eaters than modern day sharks. I'm not aware of any modern shark that readily bites through bones. This may be a function of both the greater size of the mega-toothed sharks and comparatively more powerful and robust jaws and sturdier teeth. Megalodon in particular seems pretty proficient at biting into big bones.
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Post by theropod on Nov 6, 2018 18:21:38 GMT 5
Tiger sharks readily bite through turtle carapaces, i.e. bone. I thought the evidence of this was fairly well-known (e.g. Bornatowski et al. 2012). Great white sharks have been recorded preying on turtles as well, there is even a paper about it (Ferguson et al. 2001). While they often just ingest the turtles whole, and the size disparity is much greater than for Tiger Sharks (2-3m Tiger Sharks have been recorded preying on sea turtle up to over 1m in carapace length), the paper also records direct and fatal bites into and through the carapace. They don’t seem to do this as much as Tiger Sharks, but they do it. Similar behaviour has also been suggested for sharks since the Cretaceous, including C. megalodon. I had a vague recollection of direct evidence of feeding on turtles, but I couldn’t find documentation of this in the literature (only suggestions that it may have done so). Does anybody know more on this? Shark attacks on humans also commonly involve amputation of limbs. Ergo, the sharks are perfectly capable of biting through human long bones, which are pretty big bones even by shark standards. The record of extant sharks biting not just into, but through bones is pretty solid. Bornatowski, H., M. R. Heithaus, C. M. P. Batista, and R. Mascarenhas. 2012: Shark scavenging and predation on sea turtles in northeastern Brazil. Amphibia-Reptilia 33:495–502. Fergusson, I. K., L. J. Compagno, and M. A. Marks. 2000: Predation by white sharks Carcharodon carcharias (Chondrichthyes: Lamnidae) upon chelonians, with new records from the Mediterranean Sea and a first record of the ocean sunfish Mola mola (Osteichthyes: Molidae) as stomach contents. Environmental Biology of Fishes 58:447–453.
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Post by elosha11 on Nov 15, 2018 2:56:46 GMT 5
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Post by elosha11 on Dec 30, 2018 21:39:35 GMT 5
Hey Life, hope you are doing well and Happy New Year to you. can you comment on where you found the pictures of the whale with Megalodon bite marks in the last two pictures below, the one of unknown taxa? Also, if I'm remembering correctly, back on the old carnivora many years ago you posted a picture of a relatively large rorqual skull/rostrum on which reseearchers had discovered Megalodon bite marks. Do you still have that pic and if so could you post on this thread? Thanks! Here's some great photos shared by Life in the Meg v. Livyatan thread. Really shows the incredible damage Meg could do to a whale. Here's Life's quote: [Life:] Ok, time for some visual observations:- Whale vertebra bitten in half: Whale bone with 3 inch deep gash: Whale rib bone segment with puncture like gashes: Another puncture like wound: --- Large (unknown taxon) whale killed by Megalodon? Bite wounds on same whale: --- Also, I shall make this clear that Megalodon inflicted wounds have been observed in all bodily regions of whales. Some attacking strategies have been figured out by experts; Most commonly attacked/bitten regions are: - Ribs (rib-cage) - Vertebra (spine and caudal) - Flippers
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Post by elosha11 on Jan 20, 2019 7:24:29 GMT 5
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