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RE: Gargantuavis a bird, not a pterosaur



Jason wrote-

> The ten sacral vertebrae do seem to be the character cited to diagnose
> Gargantuavis as a bird. Buffetaut and le Leouff cite Chiappe(1996), when
> they state that no non - avian dinosaur has that many sacral vertebrae.
>
> That leaves open three areas of doubt in my mind.
>
> 1) The authors were not certain of the vertebral number in Gargantuavis.
> To quote Buffetaut and le Loeuff, 1998:
>
> "...the exact number of vertebrae in the synsacrum is not easy to determine"

True, but you can make out at least nine transverse processes / sacral ribs in 
their figure.

> "...it appears that ten vertebrae are present...".
>
> 2) Have any non - avian maniraptorans been found since 1996 that have more
> than 8 sacral vertebrae?

Nope.  Only ornithuromorphs and maybe Gobipteryx.

> 3) If this type of broad, highly fused, synsacrum with neurapophyses fused
> into a low median dorsal ridge is seen in therizinosaurs such as
> Nothronychus, can we rule out the possibility that gargantuavis is a
> previously unknown species of therizinosaur?

It can't be ruled out, though sacral neural spines are fused into a lamina in 
quite a few theropods.  Similarly, lots of theropods have completely fused 
synsacra, often absent due to age.  The breadth is similar, and has never been 
used in an analysis to my knowledge.

Mickey Mortimer