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Post by kekistani on Dec 5, 2019 21:02:56 GMT 5
So in other words you could have just as easily said here that Shastasaurus lacks the anatomical adaptations for ramming and that it has virtually no weapon to its name? Hold up, first off, we don’t have a complete skull. We have enough to know Shastasaurus has a long, slender snout and a toothless pair of jaws. It wasn't designed for ramming.
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Post by kekistani on Dec 5, 2019 21:06:55 GMT 5
A megalodon fanboy, says the guys whose primary source is Max Hawthorne ? It is not fanboyism, it has already been explained here why the 2019 article by Shimada is likely incorrect and why there are great chances that megalodon TL estimates could be revised upward. I repeat again : there is at least another study about megalodon body size being done as of now. Do you understand how science works ? New studies are being done, the case of megalodon is not solved. But you persist to demonstrate how much you don't know this field of research. You even used a source proving megalodon as a predator while wanting to establish it as a scavenger ! This shows you don't even consult your own sources. What you say doesn't matter, we cannot careless if you say S. sikanniensis was a 70 tonnes animal, what matters is that you explain why. Why an animal with a body depth of barely 2.5 m maximum would weigh as much as a male Physeter. You simply don't know what you're talking about, don't you ? All what you do here is parroting Max Hawthorne fantasies. It likely has been solved. You stick with recent estimates. I just think your not going to accept the recent size. Because the "recent" size is considered an outlier by many and is probably wrong. Shastasaurus weighed nowhere near 75 tons, that estimate came from the idea it was deep bodied like Shonisaurus. It's body depth was around 2-3 meters, meaning it would weigh a similar amount to a modern day Sperm whale of 14-15 meters.
BTW, accusing someone of being a fanboy because they don't agree with your personal and unfounded opinion that Megalodon will continue to get downsized is not a good way to go about things.
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Post by Grey on Dec 5, 2019 21:48:34 GMT 5
A megalodon fanboy, says the guys whose primary source is Max Hawthorne ? It is not fanboyism, it has already been explained here why the 2019 article by Shimada is likely incorrect and why there are great chances that megalodon TL estimates could be revised upward. I repeat again : there is at least another study about megalodon body size being done as of now. Do you understand how science works ? New studies are being done, the case of megalodon is not solved. But you persist to demonstrate how much you don't know this field of research. You even used a source proving megalodon as a predator while wanting to establish it as a scavenger ! This shows you don't even consult your own sources. What you say doesn't matter, we cannot careless if you say S. sikanniensis was a 70 tonnes animal, what matters is that you explain why. Why an animal with a body depth of barely 2.5 m maximum would weigh as much as a male Physeter. You simply don't know what you're talking about, don't you ? All what you do here is parroting Max Hawthorne fantasies. Uh huh. Sure. When you said Megalodon can grow over 20 meters which is no longer accepted scientists, did you know that’s old estimate. We are sticking with recent estimates not the ones which scientists believe the most, period. Once again, you don't know what you're talking about. There are tons of links and calculations on the board explaining all the advantages and caveats about meg sizing. Crown height method suggests maximum sizes between 15 and 18 m, dentition based method suggests the large individuals did reach or exceed a bit 20 m. Such a method is definitely more solid than those based on crown or tooth height for obvious reasons (the larger the body component, the better the prediction). And those results will be published in an article soon enough. Doesn't matter you like it or not. For the last freaking time check this : www.researchgate.net/publication/308891065_SIMPLIFYING_THE_METHODS_-_BODY_LENGTH_ESTIMATES_FOR_CARCHAROCLES_MEGALODON_USING_ASSOCIATED_TOOTH_SETS_AND_JAW_WIDTH_RELATED_DATA_FROM_GREAT_WHITE_SHARKS_AND_MAKOS
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Post by Grey on Dec 5, 2019 21:51:11 GMT 5
Evidence of ramming is shastasaurids ? You see the word likely. It’s speculation. Also where’s your source? Where is a source that says the 15.3 meter long estimate is inaccurate? Ramming skill is evidenced in skull adaptations. Sperm whales have those adaptations, it appears some Tylosaurus species were maybe ramming feeders. Shastasaurus and shastasaurids so far have zero adaptations to do this. Use data and evidence, not baseless claims. Shastasaurus was toothless likely teuthophagous with a slender body profile indicating a relatively low body mass for its 21 m. Megalodon was a superpredator operating at a very high trophic level with possibly the largest bite radius in the history of life on Earth. Even a 15 m megalodon would be at least as heavy or heavier than S. sikanniensis, and the shark is infinitely better equipped to kill multi-tons prey items... This thread is totally useless.
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Post by Infinity Blade on Dec 5, 2019 23:23:59 GMT 5
I could see the Shastasaur BODY slamming, to be fair Are any marine animals even known to do this? Intuitively I think it may or may not be less practical of a maneuver underwater than on land for some reason, but I cannot confirm this.
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Post by dinosauria101 on Dec 5, 2019 23:24:50 GMT 5
I could see the Shastasaur BODY slamming, to be fair Are any marine animals even known to do this? Intuitively I think it may or may not be less practical of a maneuver underwater than on land for some reason, but I cannot confirm this. I could be wrong but I think seals and killer whales do it.
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Post by theropod on Dec 6, 2019 0:06:05 GMT 5
A fun hypothesis, though actual mosasaur people I’ve talked to seem to find the idea rather wacky. Ichthyosaurs in general would be terribly unsuited for ramming anything with their snout, ichthyosaur skulls being notable for the bones being completely unsutured and only loosely connected. If that ever even was an estimate to begin with. theworldofanimals.proboards.com/post/16947/threadThis is the holotype of S. sikanniensis (I strongly presume that sikanniensis is meant to be used here, although nobody seems to have bothered to mention it, leading to spectacularly wrong claims like "there are no complete Shastasaurus skulls, when there clearly are→) with the silhouette (scaled to 21 m) based on Guizhouichthyosaurus tangae (and it turns out quite consistent with the holotype skeleton in size when superimposing it, so I think the size estimate and the silhouette are roughly accurate). If we model its body as equally deep and wide, it comes out at around 28 t. This is the only actual estimate of S. sikanniensis’ body mass that I am aware of.
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Post by kekistani on Dec 6, 2019 1:56:03 GMT 5
Ichthyosaurs in general would be terribly unsuited for ramming anything with their snout, ichthyosaur skulls being notable for the bones being completely unsutured and only loosely connected. If that ever even was an estimate to begin with. theworldofanimals.proboards.com/post/16947/threadThis is the holotype of S. sikanniensis (I strongly presume that sikanniensis is meant to be used here, although nobody seems to have bothered to mention it, leading to spectacularly wrong claims like "there are no complete Shastasaurus skulls, when there clearly are→) with the silhouette (scaled to 21 m) based on Guizhouichthyosaurus tangae (and it turns out quite consistent with the holotype skeleton in size when superimposing it, so I think the size estimate and the silhouette are roughly accurate). If we model its body as equally deep and wide, it comes out at around 28 t. This is the only actual estimate of S. sikanniensis’ body mass that I am aware of. On ramming, wouldn't the fact that ichthyosaur skulls are elongate and thin (without the points you brought up) mean they wouldn't be good at ramming?
And on Shonisaurus, it was believed that Shonisaurus and S. Sikanniensis were the same, leading to 'Shonisaurus Sikanniensis'. This is why some books list Shonisaurus as 19-21 meters long. They assumed S. Sikanniensis was a tubby, deep-bodied animal like Shonisaurus (or at least what Shoni was thought to be like, is the superfat Shoni still accurate?) and thus, the new record heaviest and longest openly carnivorous animal was born. OFC, we now know Shasta would have weighed less than a same-sized (20M) Sperm Whale due to being a thin animal in comparison to the cetacean.
And is S. Sikanniensis now the only species of Shastasaurus? I thought what you call G. Tangae was S. Tangae
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Post by kekistani on Dec 6, 2019 2:08:07 GMT 5
I could see the Shastasaur BODY slamming, to be fair Are any marine animals even known to do this? Intuitively I think it may or may not be less practical of a maneuver underwater than on land for some reason, but I cannot confirm this. Seals do it on land, but I really don't know of any creatures that bodyslam in the water as a defense.
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Post by Infinity Blade on Dec 6, 2019 2:27:59 GMT 5
Really? I get that there's never really been a thorough test of the hypothesis (e.g. FEA), but I know at least a few paleontologists (as recently as 2018 too->) think it's at least plausible. Did you ask them what exactly they found so funny about it? I know seals do it on land (as kekistani points out) but I've never heard of them doing it underwater. Orcas ram things with the tips of their snouts or their melons. Yeah, I agree.
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Post by dinosauria101 on Dec 6, 2019 2:28:08 GMT 5
Are any marine animals even known to do this? Intuitively I think it may or may not be less practical of a maneuver underwater than on land for some reason, but I cannot confirm this. Seals do it on land, but I really don't know of any creatures that bodyslam in the water as a defense. Killer whales MAY do it in intraspecific conflict
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Post by theropod on Dec 6, 2019 2:33:42 GMT 5
On it’s own, no. Only if the skull was constructed to withstand the impact. Which ichthyosaur skulls definitely aren’t. If you rammed an ichthyosaur skull into something with any semblance of force (sufficient force to damage whatever it was ramming), the skull will probably get squished. Generally speaking, if your skull is not specially adapted for it, don’t ram it into something else. For every force, there is an equal and opposite counterforce, and chances are your own skull is actually more vulnerable (and definitely more vital) than what you are ramming. That’s why all ramming animals have heavily invested in specialized structures that allow them to use their head this way without turning them into mush. Like shock-absorbing horns, sinuses, thickened skull-roofs, spermaceti chambers, or heavily (co-)ossified and stiff rostra (though I don’t really buy into the mosasaur ramming hypothesis).
Not "superfat" (there were some restorations that went way overboard with that), but it is fairly deep-bodied, especially compared to Shastasaurus.
In fact the title for the longest probably still falls to Basilosaurus cetoides. If by "openly carnivorous" you mean everything that’s not a filter feeder (though I’ve even heard some unsubstantiated suggestions that giant shastasaurs could have been filter-feeders, because we simply don’t have a good idea of how they fed), then giant shastasaurs are probably the largest based on known specimens, yes (though not the S. sikanniensis holotype).
No and no. S. sikanniensis was referred to Shastasaurus by Sander et al. 2011, well over a century after that genus was named by Merriam in 1895, so by definition that would be impossible, whatever the type species is will always be Shastasaurus. There are three valid species in Shastasaurus, sikanniensis, S. (formerly Guanlingsaurus) liangae (of which complete cranial material is known) and the type species S. pacificus. G. tangae isn’t recovered with the other Shastasaurus species in Sander et al.’s phylogenetic analysis (instead at the base of parvipelvia), so it shouldn’t be placed in the same genus. But of course it’s G. tangae is still a related and morphologically very similar form. I also thought it was a valid species Shastasaurus back when I made the size comparison, but I think that doesn’t invalidate it as this is just a proxy for the general body shape, for which it should be fine.
On the topic of jaw size btw, it is assumed S. sikanniensis had a >3 m long skull. I don’t see how that could be considered small, though of course that is irrelevant since it doesn’t really have any biting ability. I’m observing a bit of a tendency to throw around with claims of "small" or "thin" jaws in various non-megalodon taxa based more on gut feeling than any actual data.
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Post by dinosauria101 on Dec 6, 2019 2:37:22 GMT 5
Looks like I was ninja'd.
Seems logical they'd use their melons.
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Post by theropod on Dec 6, 2019 2:38:21 GMT 5
dinosauria101 citation? No they just seemed to be very amused by the hypothesis. I think part of the problem (part of my problem too tbh) stems from the lack of any cushioning structures in the skull (a cetacean would have its melon, caprids have their horns and frontal sinuses etc.), but of course that also hasn’t been substantiated. But I see Paulina’s a coauthor on that study, so I guess my time would be spent wisely talking to her about that some time soon.
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Post by dinosauria101 on Dec 6, 2019 2:44:46 GMT 5
I gleaned it from Infinity Blade's post. You may want to ask him.
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