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ANOTHER Megaraptoran
Topic Started: Jul 21 2016, 08:13 PM (1,926 Views)
TheNotFakeDK
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the dark phoenix
Jul 25 2016, 03:28 PM
They keep comparing it to carnosaurs and Coelurosaurs so why not make it into a transitional group between the two?
Because that's not how evolutionary relationships work. Allosauroids (carnosaurs) and coelurosaurs diverged from a common ancestor at least 175 million years ago, and from then on they were two distinct lineages that coexisted with each other from then on. There can't be a "transitional group" because one didn't evolve into the other, they were sister groups, and Megaraptora must belong to either one or the other.
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the dark phoenix
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King of wonderlandia

I mean

While those two diverged, did the common ancestor just kept going? Living along side its sister groups and retaining the features of both.

A third group.
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TheNotFakeDK
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Then they would retain features shared by allosauroids and coelurosaurs from the common ancestor, but that's not what we see. Currently, megaraptorans either come out as derived allosauroids (i.e. neovenatorids), or tyrannosauroid coelurosaurs, meaning they have derived features of each group which would not be found in the common ancestor. If they did represent a distinct group, they'd have to convergently acquire features of both derived groups (allosauroids and tyrannosauroids), and I think it's fair to say that that is far less likely than them belonging to one of these groups and converged upon the other.

They only way to explain the derived traits coming from a shared ancestry were if tyrannosauroids were actually closer to allosauroids this whole time (which has a mountain of evidence against it) or if tyrannosauroids and neovenatorids somehow managed to hybridise and form an entire clade out of said hybridisation, which I think we can all agree is pretty unlikely.
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heliosphoros
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Actually hybridisation as an evolutionary mechanism is starting to be understood to be more relevant than previously thought, even among complex vertebrates like mammals.
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Incinerox
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Āeksiot Zaldrīzoti

Hybridisation between two distinct FAMILIES though?
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CyborgIguana
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I think that's happened at least with certain bird families before (though it's far from a common occurrence).
Edited by CyborgIguana, Jul 25 2016, 07:06 PM.
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the dark phoenix
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King of wonderlandia

Perhaps tyrannosauroids started going into a allosauroid niche and thus they developed the features?
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heliosphoros
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Incinerox
Jul 25 2016, 06:37 PM
Hybridisation between two distinct FAMILIES though?

Yes. High levels of hibridisation influenced Neornithes and Placental evolution, for example.

Hell, it's downright more reasonable than what happened to tunicates...
Edited by heliosphoros, Jul 25 2016, 07:30 PM.
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CyborgIguana
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Kind of off-topic but does this mean that theory proposed by that one guy a few years back that humans are actually hybrids between apes and some kind of pig potentially has more credibility than I thought?
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Acinonyx Jubatus
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CyborgIguana
Jul 25 2016, 08:08 PM
Kind of off-topic but does this mean that theory proposed by that one guy a few years back that humans are actually hybrids between apes and some kind of pig potentially has more credibility than I thought?
No. Pigs are NOTHING like humans. It's like saying porpoises are hybrids between dolphins and giraffes.
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CyborgIguana
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Didn't think so, I was just curious. Question everything and all that.
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heliosphoros
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It's considerably unlikely since humans are not more closely related to pigs than any other primate.

Plus, at least tyrannosaurs and allosaurs look enough like each other to make lust possible.
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Incinerox
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Āeksiot Zaldrīzoti

Given that tyrannosauroids and allosauroids were already very distinct in the mid-Jurassic, and already COMPLETELY different in size and build...

I'm surprised the allosauroids in question didn't try to eat the tyrannosauroids.
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the dark phoenix
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Incinerox
Jul 26 2016, 07:25 AM
Given that tyrannosauroids and allosauroids were already very distinct in the mid-Jurassic, and already COMPLETELY different in size and build...

I'm surprised the allosauroids in question didn't try to eat the tyrannosauroids.
They probably did snack on them, just not often or they got away.
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stargatedalek
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the dark phoenix
Jul 25 2016, 07:26 PM
Perhaps tyrannosauroids started going into a allosauroid niche and thus they developed the features?
Not perhaps, that's the current consensus.
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