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| T.Rex Couldn't Run?! | |
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| Topic Started: Jul 31 2017, 02:04 PM (1,340 Views) | |
| LittleLazyLass | Aug 8 2017, 08:38 PM Post #31 |
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Proud quilt in a bag
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Tom Holtz said the paper's results seemed fairly sound, merely being disappointed the method wasn't tested on extant animals first, so any idea that the paper is flawed seems misplaced. Yes, Tyrannosaurus running adaptations, but these were likely mere carry-overs from cursorial juveniles and smaller ancestors. |
totally not British, b-baka! You like me (Unlike)I don't even really like this song that much but the title is pretty relatable sometimes, I guess. Me What, you want me to tell you what these mean? Read First Words Maybe | |
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| IIGSY | Aug 8 2017, 08:43 PM Post #32 |
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A huntsman spider that wastes time on the internet because it has nothing better to do
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What you do in a panic situation is irrelevant to the actual definitions of the words |
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Projects Punga: A terraformed world with no vertebrates Last one crawling: The last arthropod ARTH-6810: A world without vertebrates (It's ded, but you can still read I guess) Potential ideas- Swamp world: A world covered in lakes, with the largest being caspian sized. Nematozoic: After a mass extinction of ultimate proportions, a single species of nematode is the only surviving animal. Tri-devonian: A devonian like ecosystem with holocene species on three different continents. Quotes Phylogeny of the arthropods and some related groups In honor of the greatest clade of all time More pictures Other cool things All African countries can fit into Brazil
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| Tartarus | Aug 9 2017, 07:11 PM Post #33 |
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Prime Specimen
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That's the argument from authority fallacy though. Just because there have been scientists who were OK with the paper doesn't automatically mean its valid and that any criticisms of it can just be ignored. Points such as how their model posed the legs incorrectly still stand and are not "misplaced" just because there have been intelligent individuals who didn't consider them. Additionally, it should be noted that the paper seems to treat stress on limb bones as it were a simple clear cut "this much stress=this reduction of the animal's speed" when it is not as simple of that. You have to also take into account things like flexibility, how the legs move, what directions and angles they move at, and so on. The way the leg bones were positioned in the study's model (in a columnar graviportal pose that is almost certainly not how they would actually have been positioned) ensure that a lot of stress will be put on them if the creature runs. More stress than would have been put on them had they positioned them properly.
I don't see why we should assume this though. This seems to be just a case of assuming that because this one new study seems to suggest a non-cursorial T-rex this must mean all the cursorial adaptations were just carry-overs. But surely a more parsimonious explanation is that these adaptations are exactly what they appear to be- evidence for the ability to run- and the study that says this couldn't happen is mistaken. |
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| TAXESbutNano | Aug 9 2017, 07:15 PM Post #34 |
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I'm going back to basics.
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I don't really know what work they put into researching posture, but perhaps the cursorial adaptations would make it faster than it would otherwise be, instead of making it fast enough to run? |
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| kusanagi | Aug 10 2017, 09:56 AM Post #35 |
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Adolescent
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Exactly how cursorial does anyone think T. rex was? Look at the crural index. The proportion of the femur length to that of the whole leg may not be the only mark of cursoriality in an animal, but it is the most important. T. rex was probably faster than some people claim but it was not some multiton roadrunner. Even most small bodied dinosaurs were not built for speed like an ostrich and those that were inhabited specific localities. You can throw in dromaeosaurid "raptors" too: some of them had thighs longer than their shins, like humans and even elephants. Throw in the claw proportions of Deinonychus resembling those of arboreal birds and there were no suferfast tyrannosaurs, no raptors running at cheetah speed. Such overstatements arose with a backlash against misinterpretations of dinosaurs as Linnean "reptiles". When talking about mammals an animal with such a degree of walking/running adaptations would never be regarded as cursorial. I already explained how rare cursoriality is among dinosaurs: I did notice an imperfect degree of correlation between habitat and cursoriality ie. the arid and open Elliot Formation. Does ventilation matter? Almost all cursorial dinosaurs were theropods with an avian airsac system, so probably. How did the few cursorial ornithischian do it? I don't know but through the Cretaceous herbivorous coelurosaurs took over small ornithischian niches which might imply respiratory superiority. Marginocephalians, thyreophorans and most ornithopods lived in the slow lane. But whatever the distribution of cursoriality in the dinosaurs the situation matches the living erect limbed fauna: not every small-ish or medium sized animal is cursorial and no multiton animals are. All the same, set a consistent definition of cursorial, and then think how to measure it, or shut up. Some discussions in pop paleo are based on the coolness of the animals (always its Tyrannosaurus never Tarbosaurus), and as much as I respect Bakker and GSP some hyperbole on the part of the dinosaur revolutionaries has spurred public misconceptions. How many people think of Tyrannosaurus as though it were a real animal, more than a century after its discovery? For most people this is about whether multiton roadrunners were real or not, there is no such fuss about giant hornless rhinos or deinotheres or the largest of hadrosaurs. Edited by kusanagi, Aug 10 2017, 11:40 AM.
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| kusanagi | Aug 10 2017, 02:55 PM Post #36 |
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Adolescent
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An interesting fact: apart from the kiwi all ratites are more cursorial than almost all nonavian dinosaurs. Yea that's right - even the robust built moas were more cursorial than many supposedly cursorial dinosaurs. Of other birds Raphus, Diaphorapteryx, Aptornis, Gastornis and Sylviornis were all perhaps typical of large theropods and other dinosaurs. Dromornis was a cursor by comparison as were at least some phorusrhacids. If you want to think how most theropods moved, look at terrestrial rallids like the weka or phasianids like the chicken (but not the more cursorial turkey) - efficient walkers capable of bursts of speed but not habitually cursorial. A roadrunner is more comparable to dinosaurs like Coelophysis. No dinosaur from the Mesozoic looks as extremely cursorial as Burhinus, seriemas or Saggitarius are, which suggests another factor is at work in the extreme crural index seen in all three of these living clades not just cursorialism. But it still suggests none of the Mesozoic theropods had a similarly specialised predatory habit despite comparisons frequently drawn between them and ie. Coelurus or Compsognathus. Edited by kusanagi, Aug 10 2017, 06:25 PM.
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| Troy Troodon | Aug 10 2017, 06:50 PM Post #37 |
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Prime Specimen
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That still wouldn't help with determining that into a larger, 7 tonne beast. I still think T.Rex could have been fast, even if it didn't technically run, at least 18-20 mph, however as it stands currently we just have to go with what we estimated so far. Edited by Troy Troodon, Aug 10 2017, 06:51 PM.
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| I was benevolent and good, but misery made me a fiend! | |
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| Tartarus | Aug 10 2017, 08:47 PM Post #38 |
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Prime Specimen
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I think you're misunderstanding the pro-running side of the debate. Accepting that T-rex could run is not the same as claiming it was some super-fast roadrunner or ostrich like thing. The issue is not whether it was a really fast runner but whether it could run at all. I think there is good evidence to show that it could. |
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| kusanagi | Aug 10 2017, 09:12 PM Post #39 |
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Adolescent
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Well of course, at least at smaller sizes. There is a reason I brought up giant rhinos and deinotheres - the former are supposedly descended from exaggeratedly "cursorial" running rhinos and the latter have been described as cursorial. Think comparative. Oh and hadrosaurs are just scaled up hypsilophodonts same as big theropods are scaled up birds. I suspect, and Mark Wotton suggests similarly, that strictly non-cursorial giants like elephants and sauropods have specific anatomical traits whereas animals like T. rex, hadrosaurs, Paraceratherium etc were at least able to run, just not at all well. Edited by kusanagi, Aug 10 2017, 09:26 PM.
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| Troy Troodon | Aug 10 2017, 09:47 PM Post #40 |
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Can you share a source to this evidence that it could run? |
| I was benevolent and good, but misery made me a fiend! | |
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| kusanagi | Aug 10 2017, 09:59 PM Post #41 |
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Speaking for myself I would simply draw attention to the non-apomorphic feet. Elephants and sauropods have specialised feet for weight bearing that involve soft tissue cushions (and a few other details). The other animals I mentioned comparatively, though they are not habitual runners, do not have what I think of as counter-cursorial adaptations to efficient walking. An animal like T.rex is not cursorial but not too far in the opposite direction either. Size aside big tyrannosaurs and allosauroids look like normal theropods, Paraceratherium is a big version of a tapir or Eohippus, and hadrosaurs are big ornithopods. Sauropods, glyptodonts and proboscideans are different for unknown evolutionary reasons that make them non-running animals: Witton overestimates the cursoriality of so-called running rhinos who have been compared to a scaled down Ceratotherium. and average sized ornithopods when he contrasts them to elephant ancestors. I would have suggested the difference is not speed but agile turning (perhaps). Something is going on in the counter-cursors other than supporting such body weight or all big animals would look the same. And throw in megatheriids - plantigrade bipeds - and we are in weird city. Of living or Holocene birds Sylviornis, Aptornis and Diaphorapteryx seem closest to T. rex, though their size and ecology were disparate. D. allegedly ate fernroot, A. is an omnivore with carnivorous tendencies and S. is interpreted as a vegetarian scratch digger. They were all built for power rather than speed and were less adapted for running than the dodo, the weka, the upland moa and other non-cursorial flightless birds. Is it possible the adzebill was the closest living analog of very large theropods? A. does have a very powerful bill like sacateurs perhaps not unlike the power bite of tyrannosaurs. Surprisingly perhaps given its gracility compared to the others, Gallus comes close but how can I tell which breed of chicken I am looking at? The femurs (thighs) of most semi-cursorial birds - Raphus, Gallirallus, Megalapteryx, Dinornis, Phasianus, Anhima, Gastornis, Casuarius - are approximately 2/3 the length of the tibia (shin part of the leg). This is normal for ground living theropods today and is seen in some theropods ie. Dromaeosaurus. As a caveat I have access to no database of crural indices so I am relying upon the skeletal reconstructions created by others, which may not be accurate, and photographs of skeletal mounts that may be subject to camera angle. All the same no nonavian dinosaur resembled stalking cursors (Pavo, Sagittarius, Burhinus, Cariama) nor noncursorial waters (Grus, Ciconia, Ardea, Phoenicopterus). Of the cursorial ratites rheas approximate the ornithomimids and alvarezsaurs the best. Edited by kusanagi, Aug 11 2017, 08:04 AM.
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| kusanagi | Aug 11 2017, 08:53 AM Post #42 |
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Adolescent
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Hypsilophodon, Jeholosaurus, Othnielia and Dryosaurus limbs are robust and the thigh is more than 2/3 of the shin. Agilisaurus is more slender but has a similar crural index, as does the non-ornithopod Heterodontosaurus. At the other extreme are Orodromeus Parksosaurus and Thescelosaurus which may all be fossorial though T. has been interpreted as aquatic. The powerful hindlimbs could have been used digging up fernroot as in Sylviornis or Diaphorapteryx. The basal genasaur Lesothosaurus is built slender with a thigh 2/3 the length of the shin as is Tianyulong. As we can see gracile ornithischians are rare and even smaller species seem to have a crural index in line with noncursorial animals. No ornithopods were cursorial when you hold them to the standards of modern avifauna. I already looked at Scutellosaurus, Pachycephalosaurus and Psittacosaurus and found them non-cursorial. I don't want to hijack the thread but claims one dinosaur could or could not ten require context ie. evolutionary relationships, possible prey in the same ecosystem, and ecological parallels. So far only ornithomimosaurs were sufficiently able to outrun big tyrannosaurs anyway and those jaws were for killing megafauna not ostrich mimics. Could Triceratops run? What about Edmontosaurus? I keep repeating about big hadrosaurs because as semi-bipeds they have the same combination of extreme weight and generalised hindlimbs structure: the hadrosaurs and tyrannosaurs likely coevolved as predator and prey. I am nowadays convinced that had there been no mass extinction of nonavian dinosaurs at the end of the Cretaceous period, all or most dinosaurs would be theropods and specifically maniraptors or therizinosaurs: only theropods were habitually cursorial reflecting the physiological superiority of saurischians (and the conservatism of sauropods), and only maniraptors and therizinosaurs had a birdlike grade of intelligence and social behaviours. Any other dinosaur survivors would by now be phylogenetic odds and sods, probably in places like NZ and Madagascar. The theropod cursors would take over in the mid tertiary and the evolution of flowers and fruits would cause a coevolution of larger brained theropods as in our own timeline. Tyrannosaurids were already marginalised in the Maastrictian as the giant hyaenodonts were in the Miocene: interestingly they also had a crushing bite as though they were convergent as macrofaunal predators, near-obligate scavengers or a bit of both. Either way such animals do not hunt elephants and rhinoceroses in our world, the last comparable giants being agriotheres. (Homo as a niche stealer outcompeting scavenging mammals?) Edited by kusanagi, Aug 11 2017, 10:59 AM.
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| Troy Troodon | Aug 11 2017, 03:05 PM Post #43 |
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Prime Specimen
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I'm sorry, I don't know for what reason exactly, but I feel both the posts you just typed are on point.
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| I was benevolent and good, but misery made me a fiend! | |
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| kusanagi | Aug 11 2017, 03:36 PM Post #44 |
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Adolescent
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Well they fi edge from the topic slightly but when they do they come back to it: T.rex phylogeny, anatomy, ecology. I just wish I could explain why sauropods, glyptodonts and elephants chose to abandon the biomechanics of running. Other megafauna limbs moved more like rhinoceroses - normal mammals - its just a few taxa that are different. But no one can compare a T.rex or a Shantungosaurus to a giant rhino instead of a living elephant - only observe a rhinoceros of any size is a better fit than an elephant. So we can't be sure the biggest rhinos could run at that weight though they were more supple than elephants or sauropods. A hadrosaurs could turn quick on its feet where an elephant can't. This incidentally meant different hunting skills were appropriate for tyrannosaurs than for Allosaurus or Majungasaurus in ecosystems with sauropod prey.
Edited by kusanagi, Aug 11 2017, 03:57 PM.
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