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Visual Comparisons
^ The elephant bird's femur is proportionately more robust that that of T-rex!
[Image: 3lt761fpevo21-Copy.png]
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Yup. It's all gotta do with changes in body plan. Birds lack tails unlike Mesozoic theropods, which would have made their bauplan more front heavy. As a result, birds had to evolve a more horizontally-oriented femur in order to place the foot below the center of mass, and therefore maintain balance without tipping forward. The more horizontally-slung femur is subjected to greater bending stresses in this position, and so this, coupled with how a) the birds in question are massive animals and b) they only have two legs bearing their weight, forces the femur to be ludicrously robust for the animal's size.
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(03-14-2019, 08:36 AM)Ausar Wrote: Yup. It's all gotta do with changes in body plan. Birds lack tails unlike Mesozoic theropods, which would have made their bauplan more front heavy. As a result, birds had to evolve a more horizontally-oriented femur in order to place the foot below the center of mass, and therefore maintain balance without tipping forward. The more horizontally-slung femur is subjected to greater bending stresses in this position, and so this, coupled with how a) the birds in question are massive animals and b) they only have two legs bearing their weight, forces the femur to be ludicrously robust for the animal's size.
^ I guess that also explains why bipedal Birds cannot grow as large as bipedal Theropods. The lack of tail seems to put too much biomechanical constraints on them so that growing any larger than that is simply not possible. Though, this makes me question why couldn't they just re-grow a tail? No? I guess that's not how evolution works lol
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And much more: http://www.geocities.jp/arctict_research...ction.html
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(03-14-2019, 08:52 AM)Verdugo Wrote:
(03-14-2019, 08:36 AM)Ausar Wrote: Yup. It's all gotta do with changes in body plan. Birds lack tails unlike Mesozoic theropods, which would have made their bauplan more front heavy. As a result, birds had to evolve a more horizontally-oriented femur in order to place the foot below the center of mass, and therefore maintain balance without tipping forward. The more horizontally-slung femur is subjected to greater bending stresses in this position, and so this, coupled with how a) the birds in question are massive animals and b) they only have two legs bearing their weight, forces the femur to be ludicrously robust for the animal's size.
^ I guess that also explains why bipedal Birds cannot grow as large as bipedal Theropods. The lack of tail seems to put too much biomechanical constraints on them so that growing any larger than that is simply not possible. Though, this makes me question why couldn't they just re-grow a tail? No? I guess that's not how evolution works lol

That's probably why. One of the limitations of natural selection, and therefore what phenotypes can be evolved, is that the basic body form for the animal is so laid out in its genes and development that it's unlikely to be altered. I'm guessing that's also the same reason why birds haven't re-evolved teeth or, if you want a wackier example, why tetrapods don't evolve extra limbs.

There is one bird I know of that evolved a very high number of caudal vertebrae (Sylviornis), but from the looks of it it was still a far cry from the long, muscular tails of its distant ancestors.
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Bear Cub and hunter

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Hand washing Jabula, a fair-sized lion.


https://www.youtube.com/watch?v=gJvITsJcgcE
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Tapir and jaguar (poor tapir did not expect it hahaha)

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Coati, agouti, tayra and collared peccary




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Genet and rhino 

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Coolest job ever

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[img=0x0]https://i.imgur.com/jaxz7aT.jpg[/img]
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T-rex vs Megatherium
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T-rex vs Purussaurus
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Saurophaganax vs Torvosaurus gurneyi
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Saurophaganax vs Torvosaurus tanneri
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Great white shark and killer whale skeleton 3d models

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