Re: Troodontidae and All That Jazz

["Timothy Williams" <twilliams_alpha@hotmail.com>]

Jaime A. Headden wrote:

> *Ornithodesmus* has been
> hypothesized as a troodont, and it too, may lie
> anywhere, as a comparison of sacra has not been done
> so far on troodonts, and I am unaware of the full
> condition in Sinorn.

Norell and Mackovicky (1997), as part of their description of two new 
velociraptorine specimens, suggested that _Ornithodesmus cluniculus_ might 
be a dromaeosaurid.  _O. cluniculus_ is known only from a sacrum.  In this 
sacrum, like that of dromaeosaurids, the fused zygapophyses form a sinuous 
ridge (on either side of the fused neural spines).  In troodontids, this 
ridge is straight.

It would be interesting to compare the _Ornithodesmus_ sacrum with that of 
_Variraptor_.


Tim

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