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Re: Gigantoraptor stuff
Pedro Andrade wrote:
Even if Gigantoraptor is not Deinocheirus,
In the most recent analysis, _Deinocheirus_ came out as a gigantic
ornithomimosaur, close to _Harpymimus_.
bugs me: is there any special reason why Late
Cretaceous maniraptoriforms in Mongolia grew so large?
Apart from Gigantoraptor and Deinocheirus there's also
giant therizinosaurids and Achillobator.
Yeah, it bugs me too. Maniraptoriforms appear to have radiated into the
"large herbivore" role dominated by sauropodomorphs and ornithischians. In
Iren Dabasu, for example, there are plenty of theropods, a few runty
hadrosaurs, but no sauropods (AFAIK - if I'm wrong on this, please let me
know). Derived therizinosauroids appear to have been herbivores, and the
same might be true of at least some oviraptorosaurs (hence my previous
comparison of _Gigantoraptor_ to _Dinornis_). I don't know about
_Deinocheirus_ - although its placement among basal ornithomimosaurs
suggests that it was perhaps not a ferocious predator... but I wouldn't want
to go too far with that. Somebody had the intriguing suggestion that
_Deinocheirus_ was specialized for digging up small ornithopods from their
burrows (which, if nothing else, would make for a great illustration).
But _Achillobator_ was certainly a predator. It had plenty of big
herbivores to go after.
Why did this happen in Mongolia and not say, North America?
It might have - especially if tyrannosauroids are maniraptoriforms. North
America also had large dromaeosaurs (e.g., _Utahraptor_), some
therizinosauroids, and at least one large oviraptorosaur (undescribed; and
not as humongous as _Gigantoraptor_).
Hope that helped.
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