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Augusto Haro <email@example.com> wrote:
> Instructive point (congratulations dude, it's incredible how much you know!).
> But, were there enough cycads, or similarly though plants, to allow
> therizinosaurs prospering by eating them? Because a group which
> declines in taxonomic diversity may still be a conspicuous element of
> the biota.
> If not, it has been hypothesized that ceratopsians, which also
> diversified close in time, also dealt with though plants. Ostrom
> considered Triceratops was feeding upon palms and cycads, later others
> stated that they may be feeding on though ferns, which were more
> abundant. May something like that also apply to therizinosaurs? Long
> and blade-like claws may be useful for some plant with a robust main
> body protected by hard (preferably flexible) walls but with some
> softer inside.
Even among the derived/post-_Falcarius_ therizinosaurs the function of
the forelimbs probably varied between individual taxa. Although the
claws of _Therizinosaurus_ were very long and blade-like, those of
taxa like _Nothronychus_ and _Erliansaurus_ were shorter and strongly
recurved. So it is possible that the latter used their manus to help
procure food, whereas the extreme condition in _Therizinosaurus_ was
tied solely to the use of the forelimb as a weapon.
That doesn't rule out less derived therizinosaurs also using their
hand-claws for defense - these pot-bellied herbivores certainly
couldn't run from danger. But it may be that the trophic role of the
forelimbs became progressively less important, and the long claws of
_Therizinosaurus_ took on a role in defense against potential
predators, or in sexual display (as suggested by Zanno, 2006). The
giant claws could have been like the antlers of the "Irish elk", and
not even used for intraspecific combat.