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Post by coherentsheaf on Jun 17, 2015 3:50:36 GMT 5
Hmm, in a symmetric distribution of describing a population, isn’t the mean right in the middle, the value at which the probability function has its maximum? Doesn’t that make it equally likely that the mean is lower and that it is higher than the size of any given individual? I mean that I understand the reasoning from absolute size, I just don't spot where it figures into the distribution. If you assume you know the mean, you have no way to tell inwhich way your distribution goes a priori. So you assume it is symmetrica because this represents your state of knowledge- indifference regarding the skew of the distribution around the mean. But we do not know the mean, we just make assumption about how x would fall around it. It is all quite confusing, your verbal statement is kinda correct.
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Post by theropod on Jul 12, 2015 5:18:57 GMT 5
Bitten whale vertebra with (associated ?) megalodon tooth. Found this as a byproduct of searching for pics of meg vertebrae; Similar pieces of meg teeth shown embedded in vertebrae are usually fakes, montages of completely unrelated specimens that were not actually found in association, with the tooth embedded artificially to make for a more interesting "artistic" composition: www.fossilsonline.com/index.php?main_page=product_info&products_id=1794www.fossilsonline.com/index.php?main_page=product_info&products_id=1795museumgeek.org/page_4.htmlWhat’s suspicious in this one is that, like the above examples, the tooth is stuck almost perpendicular in the articular surface of the centrum, where it wouldn’t end up by natural means of any imaginable shark bite, save for an enormous coincidence of one happening to accidentally bite down on a completely disarticulated vertebra. It is also not typical to have a puncture wound that still matches up with the tooth so well that it can be neatly stuck back, usually the wounds are enlarged into scratchmarks from the drawing motion of the teeth. So I advise great caution regarding this specimen and similar ones in general. Especially, make sure to check the pages they come from for more information before accepting them.
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Post by Grey on Jul 13, 2015 4:01:46 GMT 5
I know since a while this is a staged piece.
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Post by theropod on Jul 13, 2015 14:37:20 GMT 5
All the better then, now the rest of us do too.
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Post by Infinity Blade on Sept 28, 2015 6:48:38 GMT 5
Oh, something I forgot to mention. In regards to the Carnivora variant of this topic, I absolutely adore how Sam1 called people "infantile" (who I presume included me, if not exclusively me) just because we said that Livyatan's greater intelligence wouldn't be a godsend that would allow it to win 90% of the time IIRC (in a rebuttal to another member). Smh.
His statement that Livyatan's greater intelligence would enable it to be smart enough to ram instead of get in a biting contest doesn't even hold water IMO. As others pointed out on that thread, I really don't think the intelligence (or probably more like instinct) that tells the whale to ram would be any different than the instinct that tells it (or the shark) to bite.
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Post by Grey on Sept 28, 2015 13:32:54 GMT 5
Sam1 has always been a cetacean fanatic who thinks toothed whales are martial artists and nuclear physicists at the same time.
The whale was certainly intelligent but comparable to modern cetaceans ? It is certainly more primitive than the modern sperm whale. The modern sperm whale has the largest brain on Earth yet it does not exhibit an exceptionnal intelligence.
As for the ramming, it would have been certainly potent but probably less than in a modern male sperm whale, the supratemporal bassin and the whole body size are both smaller than in the modern male sperm whale.
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Post by theropod on Sept 28, 2015 18:28:10 GMT 5
Can someone recommend me any studies regarding sperm whale intelligence, beyond the fact that they exhibit advanced social behaviour and communication that are typical of cetaceans? Livyatan’s body size is comparable to extant male Physeter. The lower length estimate is comparable to the average adult male. It’s bizygomatic width is well above the average zygomatic widths of male Physeter in Lambert et al.’s dataset. I agree that Physeter is not necessarily the best analogue for its ramming ability considering the difference in cranial anatomy. Even so, there are other odontocetes have very potent rams, with orcas (with proportionately smaller skulls than any physeteroid, and no spermaceti chamber at all) using it to kill prey items of comparable size to themselves such as minke whales (Ford et al. 2005), being able to catapult adult false killer whales 10m high into the air (Visser et al. 2010) as well as recorded breaching the hulls of 13m sailboats ( source→). If anything, this may become more deadly at larger sizes due to greater force being excerted over a given area in the collision of two 50t animals compared to two 5t ones. There can be no doubt about the potency and relevance of Livyatan’s ram imo. –––References:Ford, John K. B.; Ellis, Graeme M.; Matkin, Dena R.; Balcomb, Kenneth C.; Briggs, David; Morton, Alexandra B. (2005): Killer Whale Attacks on Minke Whales: Prey Capture and antipredator Tactics. Marine Mammal Science, 21 (4), pp. 603–618. Visser, Ingrid N.; Zaeschmar, Jochen; Halliday, Jo; Abraham, Annie; Ball, Phil; Bradley, Robert; Daly, Shamus; Hatwell, Tommy; Johnson, Tammy; Johnson, Warren; Kay, Laura; Maessen, Tim; McKay, Vanessa; Peters, Taira; Turner, Nathan; Umuroa, Basil; Pace, Daniela S. (2010): First Record of Predation on False Killer Whales (Pseudorca crassidens) by Killer Whales (Orcinus orca). Aquatic Mammals, 36 (2), pp. 195-204
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Post by creature386 on Sept 28, 2015 18:40:37 GMT 5
Random fact: I just discovered a "Livyatan wins because it was more intelligent" comment under my meg vs liv video after reading the discussion above. theropodIf I understood the paper below correctly, sperm whales are a match for dolphins when it comes to intelligence, despite phylogenetic distance. Increasingly, it seems that the social competition hypothesis may be the best explanation for all three ‘peaks’ in mammalian brain size: humans (and apes), elephants and odontocetes (primarily delphinids and sperm whales).[…] (c) The sperm whale and the elephant A major early increase in odontocetes’ brain size took place roughly 35 Myr ago (Marino et al. 2004). The more recent expansion of the brain in delphinids occurred about 15 Myr ago (Marino et al. 2004), long after sperm whales split from other toothed whales (Heyning 1997). The large sperm whale brain may have evolved independently, eased as well by a squid and fish diet, and additionally, a large body size. As noted by Whitehead (2003), the fraction of metabolism devoted to the brain depends on relative brain size which declines with increasing body size. Simply, other things being equal, big brains are cheaper for larger animals such as elephants and sperm whales. Elephants do not consume the high quality food of sperm whales, but may compensate by processing a lot of food at a high rate (Clauss et al. 2003).rstb.royalsocietypublishing.org/content/royptb/362/1480/587.full.pdfBut the intelligence of sperm whales really was a recent invention, I am not 100% sure if Livyatan was as intelligent as the modern sperm whale.
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Post by theropod on Sept 28, 2015 19:13:06 GMT 5
Where’s the CT-scan when you need it? Well, it depends entirely on how early in their evolution large brain size evolved in physeteroids, which sounds like an interesting subject for future studies (surprised it wasn’t so far actually). Certainly macrophagous taxa would be subject to similar selective pressures to equivalent delphinids in terms of cognitive ability so there’s a reason to think large brains evolved in this context. Livyatan may have been an early physeteroid, but it was also already a very derived animal in terms of size and ecology.
Lol I just recently read someone on deviantart comment regarding this subject, stating something along the lines of "Mismatch, toothed whales need a size advantage against sharks and Livyatan is smaller!!!". Then there’s the other extreme, like the guy on CF who claimed something like "Livyatan wins 90% of the time because of intelligence!!!!". It’s a shame that giant predators draw so many people with stupid and biased opinions…
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Post by Grey on Sept 28, 2015 20:36:44 GMT 5
A predator, not only toothed whales, needs primarily a size advantage to subdue another predator with a similar killing apparatus.
With time I become more and more convinced that the holotype of Livyatan was around 15 m, it is listed in the recent thesis by Alexandra Boersma as smaller than Physeter, which means the large Carcharocles representatives would have the edge but I try to get confirmation from Lambert et al.
Regarding intelligence, I've failed to ever see how it can be a decisive advantage in such a contest (given that such contest between apex predators very rarely occures and are even less documented).
Regarding the orca sinking the 13 m Lucette off the Galapagos, I had read the story from the survivors and just before the sinking they had remarked one of the orcas was bleeding to death, they presumed it was the one having rammed them.
But any large marine animal can be dangerous while ramming, sperm whales are certainly particularly adapted to this but records of small boats capsized by even smaller sharks exist too.
Brett Kent even suggests Carcharocles could ram into its preys at first and debilitate them without even biting them.
I tend to revise my statement time to time but I still go with the giant shark.
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Post by theropod on Sept 28, 2015 21:34:45 GMT 5
Boersma was only considering Physeter "by far the largest" because she was using condylobasal length as a proxy for size and because Physeter has a much more elongated rostrum than Livyatan.
Do you have evidence of any shark killing something of similar body size with a ram, or penetrating the hull of a boat?
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Post by Grey on Sept 28, 2015 22:04:24 GMT 5
But Boersma focus is about body size. I've calculated the size of Livyatan based on her estimate of Ochyrodon derived from Physeter and Kogia antorbital notch width and I get 14.5-15 m TL for Livyatan. Added to the uncertainties regarding the reliability of the 6.5-7 m for Zygophyseter and Brygmophyseter, I think it's a the most realistic figure. So that's comparable to the lower size of adult male Physeter but not to the large ones. I wait for a comment by Lambert regarding the reliability of the size estimate of Zygophyseter. I'll search about the accounts I had read about sharks sinking boats, they're now more difficult to access because of the buzz of the mockumentary about a megalodon sinking a boat off South Africa. Note I've said nowhere that a modern shark was known to have killed a similar-sized prey by ramming. A bull shark sunk a shrimp boat in 2007 www.underwatertimes.com/news.php?article_id=37456191080
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Post by theropod on Sept 28, 2015 22:25:48 GMT 5
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Post by Grey on Sept 28, 2015 22:32:38 GMT 5
Sperm whales yes, I'm not that convinced for orcas. That large sharks don't usually use ramming to kill their preys does not say their ram is not potent.
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Post by theropod on Sept 28, 2015 22:35:43 GMT 5
Sperm whales yes, I'm not that convinced for orcas. That large sharks don't usually use ramming to kill their preys does not say their ram is not potent. I think saying that something’s ram is sufficient to be used as a killing weapon against a similar-sized opponent requires evidence. Such evidence exists for whales, but not for sharks.
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