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Post by theropod on Jun 19, 2019 19:39:39 GMT 5
There has been a published computational simulation suggesting it could have…
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Post by dinosauria101 on Jun 19, 2019 21:38:51 GMT 5
sam1 It may be of interest to you that this comparison posted earlier also has European hippopotamus and Elasmotherium  Yeah I think I saw that one, sameer has a ton of great megafauna and dinosaur comparisons. But I have to add this new spinosaurus depictions are just a no go for me. I don't doubt the anatomy, but I don't think it could've walked bipedal like that. I myself am kind of on the fence about it. A few discoveries should help out |
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Post by sam1 on Jun 21, 2019 16:35:49 GMT 5
There has been a published computational simulation suggesting it could have… I wouldn't put much trust into "computational simulation" of a bipedal locomotion of such unorthodox body plan. These simulations are still limited (unless done specifically on a super computer and practically tested.) Consider how long it took for robotics to develop legit bipedal system. |
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Post by dinosauria101 on Jun 21, 2019 16:43:12 GMT 5
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Post by sam1 on Jun 21, 2019 23:23:24 GMT 5
Thanks, that was an interesting read. Spinosaurus was surely one of the most intriguing dinosaurs! |
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Post by dinosauria101 on Jun 21, 2019 23:27:22 GMT 5
Thanks, that was an interesting read. Spinosaurus was surely one of the most intriguing dinosaurs! Most definitely, I agree! This study also lets me invalidate the hollering of 'mismatch' in the T rex vs Spino thread. Yes, it is a mismatch in favor of Rex....on LAND. In water, the opposite is true and Rex has no chance On a slightly more serious note though, this study does help to justify matching Spino up with Cretoxyrhina and Predator X |
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Post by creature386 on Jun 21, 2019 23:45:28 GMT 5
This study was published well before Henderson's (https://doi.org/10.7717%2Fpeerj.5409 ) and gives no reason to doubt it.
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Post by dinosauria101 on Jun 21, 2019 23:53:02 GMT 5
That's pretty close to a hippo or a Nile crocodile, neither of which venture into SUPER deep water, but do fine in medium water
I think matchups with Spino and water are still justifiable in that sense
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Post by theropod on Jun 22, 2019 0:53:20 GMT 5
There has been a published computational simulation suggesting it could have… I wouldn't put much trust into "computational simulation" of a bipedal locomotion of such unorthodox body plan. These simulations are still limited (unless done specifically on a super computer and practically tested.) Consider how long it took for robotics to develop legit bipedal system. No, current computers are more than adequate to calculate the center of mass of a known geometrical shape, there’s really little to question about it on those grounds. Sorry if "computional simulation" is a misleading term, what I meant to say was that it was rigorously, quantitatively confirmed that the animal could in fact stand upright, contra your claim that its body shape could not be supported bipedally. There are issues I have with Henderson’s study, such as the lack of discussion of the accuracy of the model itself (e.g. the vertebral placement, and assumptions about the sail shape) and the assumption that airsack size and body density were the same for all theropods. But these do not make it more likely that the animal was a quadruped. If anything those parts that were comparatively more dense in Spinosaurus are relatively close to the hip and would tend to shift the COM backwards more than in certain other theropods, where the sacrum and even tail can be pneumatized extensively, and the shape of the "sail" as reconstructed by Ibrahim et al does more to shift the COM anteriorly than many previous reconstructions, even though it’s accuracy is still in doubt. So the study’s results still stand, and they are a whole lot better than any visual guesstimate off a skeletal. Apart from the fact that in well over 10 000 species of theropods, not a single one is quadrupedal, no quadrupedal adaptations of the forelimb have ever been described or even mentioned for any spinosaur (or any other fossil theropod for that matter). A 7t animal won’t just decide its forelimbs, despite being wholly unsuitable for that, will do fine for walking on them now, and then start walking quadrupedally. That’s an elephant-sized animal, it’s limbs would need weight-bearing adaptations, at least equivalent to those seen in large knuckle-walking mammals. The burden of proof should rest on those making the claim that Spinosaurus could not walk bipedally, not the other way around (even though said evidence for the latter has already been provided). |
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Post by dinosauria101 on Jun 22, 2019 1:00:22 GMT 5
A 7t animal won’t just decide its forelimbs, despite being wholly unsuitable for that, will do fine for walking on them now, and then start walking quadrupedally. That’s an elephant-sized animal, it’s limbs would need weight-bearing adaptations, at least equivalent to those seen in large knuckle-walking mammals. The burden of proof should rest on those making the claim that Spinosaurus could not walk bipedally, not the other way around (even though said evidence for the latter has already been provided). I've seen some stuff floating around on Carnivora about Spino being unable to bear walking weight on its forelimbs. Do you know the study that came up with that? EDIT: sam1, if you're reading this, it's directed at theropod (though if you have the answer, feel free to post it). The text just changed boxes during my reply |
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Post by theropod on Jun 22, 2019 1:31:01 GMT 5
There are a number of anatomical adaptations for knuckle-walking even in modest-sized Myrmecophaga and primates (Orr 2005). I’m not sure if there have been detailed studies on the manus of chalicotheres or ground sloths, but I recall blaze made some mention of specifically adapted metacarpals in those taxa.
Orr, C.M. 2005. Knuckle-walking anteater: A convergence test of adaptation for purported knuckle-walking features of african Hominidae. American Journal of Physical Anthropology 128 (3): 639–658.
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Post by sam1 on Jun 22, 2019 2:47:24 GMT 5
I wouldn't put much trust into "computational simulation" of a bipedal locomotion of such unorthodox body plan. These simulations are still limited (unless done specifically on a super computer and practically tested.) Consider how long it took for robotics to develop legit bipedal system. No, current computers are more than adequate to calculate the center of mass of a known geometrical shape, there’s really little to question about it on those grounds. Sorry if "computional simulation" is a misleading term, what I meant to say was that it was rigorously, quantitatively confirmed that the animal could in fact stand upright, contra your claim that its body shape could not be supported bipedally. There are issues I have with Henderson’s study, such as the lack of discussion of the accuracy of the model itself (e.g. the vertebral placement, and assumptions about the sail shape) and the assumption that airsack size and body density were the same for all theropods. But these do not make it more likely that the animal was a quadruped. If anything those parts that were comparatively more dense in Spinosaurus are relatively close to the hip and would tend to shift the COM backwards more than in certain other theropods, where the sacrum and even tail can be pneumatized extensively, and the shape of the "sail" as reconstructed by Ibrahim et al does more to shift the COM anteriorly than many previous reconstructions, even though it’s accuracy is still in doubt. So the study’s results still stand, and they are a whole lot better than any visual guesstimate off a skeletal. Apart from the fact that in well over 10 000 species of theropods, not a single one is quadrupedal, no quadrupedal adaptations of the forelimb have ever been described or even mentioned for any spinosaur (or any other fossil theropod for that matter). A 7t animal won’t just decide its forelimbs, despite being wholly unsuitable for that, will do fine for walking on them now, and then start walking quadrupedally. That’s an elephant-sized animal, it’s limbs would need weight-bearing adaptations, at least equivalent to those seen in large knuckle-walking mammals. The burden of proof should rest on those making the claim that Spinosaurus could not walk bipedally, not the other way around (even though said evidence for the latter has already been provided). The issue I see is not the center of gravity but the feet. They are not providing nearly enough surface for the counter force balancing. In other words, it can be easily calculate d if a model of such animal could have stood upright providing its feet are solidly planted to the ground. But the complete movement and feet mechanics are immensely more complex thing that can't be calculated. They would need to create an accurate robotic reconstruction controlled by a software that is beyond the current bleeding edge. |
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Post by dinosauria101 on Jun 22, 2019 11:44:46 GMT 5
African lion vs lower (but bulkier, likely still meaning 500 kg) size estimate of Shaochilong from Carnivora  |
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Post by dinosauria101 on Jun 23, 2019 16:50:55 GMT 5
Allosaurus fragilis vs Daspletosaurus from DPF  |
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Post by dinosauria101 on Jun 24, 2019 17:36:16 GMT 5
African lion vs grizzly bear from Photobucket  |
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