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Birds With Multiple Origins; Birds a polyphyletic group?
Topic Started: Mar 24 2010, 03:18 PM (576 Views)
Toad of Spades
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What if every group of maniraptoran produced something along the lines of what would a true bird? This would mean that "birds" would have evolved multiple times during the Mesozoic. Also what if true birds and "false" birds survived the K-T Extinction? That would mean alvarezsauroids, deinonychosaurs, oviraptorsaurs, and therizinosauroids all survived in some form. Then what if they all conformed to the features of true modern birds? That would mean that birds would be a polyphyletic group.

What are your thoughts about this, how likely do you think this is, and do you think that something like this could have happened and it is possible that birds really are a polyphyletic group?

I think that it is very likely that something like this could have happened. I also think that birds could be a polyphyletic group, considering that some oviraptorsaurs have a pygostyle and that many features unique to "birds" are already present in many maniraptorans. I think that it is possible that birds could have evolved from two or more lines of maniraptorans.
Edited by Toad of Spades, Mar 24 2010, 03:19 PM.
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The Dodo
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I don't it's likely that some of them like alvarezsaurs would evolve flight considering the size of their arms.
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Carlos
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Its a nice idea, but sadly I don't think it'd work. A particular group would eventually replace the others; unlike bats or pterosaurs flying maniraptors would more or less have the same body plan and as such occupy similar niches, which would rule out competing groups till only one or two remained. On our world, by the late Cretaceous non-avian winged maniraptors like dromeosaurs were already ruled out to forms like Rahonavis and maybe a few others, the rest of dromeosaurs having becomed flightless, and even among birds Euornithes were triumphing, with only Enantiornithes offering significant competition, with maybe a few groups as relics.
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Practically Uninformed
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If by "bird" you mean a flying, feathered animal, than no, that might not work.
But if a "bird" is merely a creature that's very similar to a bird (beak, wings, feathers, etc.), that might be concievable.
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Ook
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how about http://povorot.deviantart.com/gallery/#The-World-They-Live-In :)
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Carlos
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Those are bird like troodontids right, but at least they don't fly (the only ones that do so are very marginally placed in the ecological niches)
Lemuria:
http://s1.zetaboards.com/Conceptual_Evolution/topic/5724950/

Terra Alternativa:
http://s1.zetaboards.com/Conceptual_Evolution/forum/460637/

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colddigger
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if they filled different niches (true birds high up, false birds down low) so that their paths didn't cross and there was virtually no competition then it might work.

but they would have had to develop around the same time so that neither ones hold on their niche was particularly weaker than the other, so that when both became developed enough to even attempt taking the others niche there would be a stand still...
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Margaret Pye
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Modern birds are definitely monophyletic. I've heard a theory that maniraptors evolved flight more than once (Rahonavis seems pretty aerodynamic, and there are doubts over whether it's closely related to Archaeopteryx), but I don't know how reputable the theory is.

Sorry, John, but that incredibly cool theory Gregory Paul came up with, about all dromaeosaurs being secondarily flightless? It seems to be wrong. The more primitive the dromaeosaur, the less birdy it is. Pity.

Simon Roy does have a few flying troodonts, including one that his dinosauroids domesticated as a hunting companion. None of them are very good at flying, though - they avoid competition with real birds by mostly occupying terrestrial or arboreal niches, and flying only in an emergency. (I used the same idea to keep a few Archaeopteryx-grade birds around in a KTless world that had evolved sparrows and falcons.)

Would Euornithes necessarily have outcompeted Enantiornithes if the meteor hadn't intervened? Maybe they would have both survived, perhaps in different niches or on different continents.
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Carlos
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Quote:
 
Would Euornithes necessarily have outcompeted Enantiornithes if the meteor hadn't intervened? Maybe they would have both survived, perhaps in different niches or on different continents.


In the original version of Spec, enantiornithes had been reduced to something akin to galliforme analogues while the euornithes had diversified. I don't think the competition between both groups would reach such a point in a KT less present - Enantiornithes were still relatively diverse, specially on terrestrial niches, and were exploring aquatic ones as well - but I have no doubts that they could slowly decline in favor of euornithes
Lemuria:
http://s1.zetaboards.com/Conceptual_Evolution/topic/5724950/

Terra Alternativa:
http://s1.zetaboards.com/Conceptual_Evolution/forum/460637/

My Patreon:

https://www.patreon.com/Carliro

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Zorku
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colddigger
Mar 24 2010, 05:41 PM
if they filled different niches (true birds high up, false birds down low) so that their paths didn't cross and there was virtually no competition then it might work.

but they would have had to develop around the same time so that neither ones hold on their niche was particularly weaker than the other, so that when both became developed enough to even attempt taking the others niche there would be a stand still...
In other words multiple origins of birds is very un-parsimonious.
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