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Post by Supercommunist on Oct 1, 2013 9:47:40 GMT 5
This has been a question that has perplexed me for years. Was earth's oxygen level back then higher allowing some dinosaurs to reach masses impossible for animals of today? Was earth's gravity lower back then? Or was it something else entirely diffrent?
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Post by creature386 on Oct 1, 2013 12:58:35 GMT 5
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Deleted
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Post by Deleted on Oct 1, 2013 21:10:33 GMT 5
Was earth's oxygen level back then higher allowing some dinosaurs to reach masses impossible for animals of today? No, because although it did rise during a few occasions, it did not by a truly significant amount. And dinosaurs breathe through an avian respiratory system, not insect spiracles. NOPEYes Biggest Dinosaurs Grew Huge by Not Chewing Their Food |
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Fragillimus335
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Sauropod fanatic, and dinosaur specialist
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Post by Fragillimus335 on Oct 2, 2013 4:05:59 GMT 5
The general consensus is that the bird-like respiratory system of dinosaurs allowed them to be far more efficient than mammals, and thus attained much larger sizes. The oxygen and gravity levels were almost exactly the same. Hollow bones also help.
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LeopJag
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Panthera kryptikos (cryptic, evasive panther)
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Post by LeopJag on Oct 2, 2013 7:25:41 GMT 5
Was earth's oxygen level back then higher allowing some dinosaurs to reach masses impossible for animals of today? No, because although it did rise during a few occasions, it did not by a truly significant amount. And dinosaurs breathe through an avian respiratory system, not insect spiracles. Sorry, that one had me loling...  |
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Post by dinosauria101 on May 21, 2019 20:31:01 GMT 5
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Post by creature386 on May 23, 2019 0:57:37 GMT 5
A little bit basic, but probably spot on. Thanks for posting this! I'd add ovipary to the list of advantages (giving life birth must be painful at these sizes).
Of these advantages dinosaurs had over mammals, I wonder which would be the easiest and which would be the hardest for hypothetical sauropod-mammals to attain (this is more of a spec evolution than a zoology question, but I guess it still fits). I could imagine them giving up chewing (probably the easiest) or evolving some sort of gigantothermy. An avian respiration system, hollow bones and ovipariy on the other hand would be much less likely to evolve.
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Post by Infinity Blade on May 23, 2019 1:22:17 GMT 5
^The hypothetical mammal could be a monotreme, lol! We can also add limb joint scaling effects to the list. I've cited a work before showing that as terrestrial mammals get larger, their limb joints become narrower with thinner articular cartilage, but become more close fitting, something that can only work so far. Archosaurs, though, get wider limb joints with thicker articular cartilage; the joints from the bones themselves become less close fitting, but I think the joints from the articular cartilage fit each other more ( Bonnan et al. 2013). |
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Post by creature386 on May 23, 2019 1:35:16 GMT 5
^The hypothetical mammal could be a monotreme, lol! I got that idea after composing the post, too. I wonder if we should take this into account or use the mammal groups known to attain giantism as a baseline. Very interesting mention of joint scaling effects BTW, this is the first time I'm hearing this. Since we seem to be talking about plesiomorphies in bone structure here, I'd add that to the "Hard to evolve" list. |
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Post by dinosauria101 on May 23, 2019 1:48:40 GMT 5
^I only posted that because I thought it would've had information about why the dinosaurs got large (this was after reading it btw)
theropod why did you like that post? That wasn't intended to take things off topic nor to be basic. I actually thought it would've had relevant stuff for the thread
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Post by Infinity Blade on May 23, 2019 1:51:07 GMT 5
^The hypothetical mammal could be a monotreme, lol! I got that idea after composing the post, too. I wonder if we should take this into account or use the mammal groups known to attain giantism as a baseline. Very interesting mention of joint scaling effects BTW, this is the first time I'm hearing this. Since we seem to be talking about plesiomorphies in bone structure here, I'd add that to the "Hard to evolve" list. I actually posted this on some Carnivora topic before it moved to Tapatalk; I think you were one of the people who posted in that thread (and probably read my post). But yeah, whatever the case, this hypothetical terrestrial mammal would basically have to defy the scaling laws of its entire clade to help it grow larger. The monotreme quip was semi-jocular. I'm wondering the same thing as you are about them. |
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Post by creature386 on May 23, 2019 1:53:46 GMT 5
^I only posted that because I thought it would've had information about why the dinosaurs got large (this was after reading it btw) It was not supposed to be a criticism, I just wanted to say something about your article. My criticism was (if at all) more directed at the article's author than you. I can see why you were a bit sensitive after that wave of criticism though. Edited the post to make that more clear. @ausar Alright, I'll take the solipsist's stance and declare that anything not in my memory never took place. Joke aside, yup, I read it: www.tapatalk.com/groups/carnivora/viewtopic.php?f=7&t=5469&p=378898&hilit=Bonnan#p378898 |
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Post by theropod on May 23, 2019 3:40:04 GMT 5
dinosauria101. That had nothing to do with the "basic"-thing. That being said, I read the comment before it was edited, and saw nothing wrong with it. I liked creature's post because, being a sauropodomorph researcher myself, I find the question of what enabled them to achieve their unparalleled size very interesting, and wanted to agree with creature regarding his spec-evo hypotheses, which is likewise interesting since it relates to what might be the limits on mammalian body size, and how hard those limits are. One thing to add on that might be the supposedly pleurocoel-like fossae in Paraceratherium vertebrae. I've only read mentions of these a few times, but no detailed study, but they are quitr interesting. Obviously those would not be correlates of an airsac system, but that a mammal can apparently lighten the skeleton at least somewhat in this manner is interesting.
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Post by dinosauria101 on May 23, 2019 3:44:29 GMT 5
dinosauria101 . That had nothing to do with the "basic"-thing. That being saiid, I read the comment before it was edited, and saw nothing wrong with it. I liked creature's post because, being a sauropodomorph researcher myself, I find the question of what enabled them to achieve their unparalleled size very interesting, and wanted to agree with creature regarding his spec-evo hypotheses, which is likewise interesting since it relates to what might be the limits on mammalian body size, and how hard those limits are. One thing to add on that might be the supposedly pleurocoel-like fossae in Paraceratherium vertebrae. I've only read mentions of these a few times, but no detailed study, but they are quitr interesting. Obviously those would not be correlates of an airsac system, but that a mammal can apparently lighten the skeleton at least somewhat in this manner is interesting. Ah, okay. That's just fine. Also, don't some sauropods have pleurocoels as well? |
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Post by theropod on May 23, 2019 3:47:47 GMT 5
Yes of course!
Pleurocoels in a dinosaur are totally normal, the strange thing is finding analogous structures in a mammal.
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