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Re: Ah ha! That's where therizinosaurs came from



<GSP1954@aol.com> wrote:

> One reason I realized that dromaeosaurs were likely to be neoflightless
> was
> because when I examined the Eichstatt specimen in 81 was it was plain as
> day that the palate was theropodian not avian in grade, so that did in the
> argumment that it was a "bird" more derived than dromaeosaurs since Archy
> does
> not have a whole lot else indicating it is closer to modern avians than the
> sickle claws. I also learned on the same trip that dromaeosaurs had
> ossified
> uncinates and sternal ribs in addition to the big sternal plates and
> pterosaur like tail also absent in Archy, plus the folding arms. I figured
> I would
> just wait oh about 30 years for the winged dromaeosaur fossils to show up
> supporting the hypothesis. So it's a mixture of flight adaptations and
> phylogeny.


Assuming that _Archaeopteryx_ is closer to dromaeosaurs than to birds,
the "neoflightless-ness" of dromaeosaurs only holds if _Archaeopteryx_
could actually fly.  The discovery of winged dromaeosaurs contributes
little if anything to the "neoflightless" hypothesis, since it only
shows that a common ancestor of _Archaeopteryx_, dromaeosaurs, and
birds had wings - not that it was volant.


As for "folding arms" being an indication of flight ability (or former
flight ability).... let's not get carried away.  Some
limited/incipient arm-folding ability, as conferred by a trochlear
semilunate carpal, is widespread among tetanurans, including
_Allosaurus_ (Chure, 2001), _Tanycolagreus_ (Carpenter et al., 2005; =
hand originally referred to _Ornitholestes_), and many, many more.




Cheers

Tim