Re: Falcarius utahensis (was RE: Newfound Dinosaur a Transitional Creature)

["Jaime A. Headden" <qilongia@yahoo.com>]

Tim Williams (twilliams_alpha@hotmail.com) wrote:

<The anatomy of _Falcarius_ indicates that the teeth (small, leaf-like) and 
pelvis were among the first things to change in the transition from carnivory
to herbivory in therizinosauroid evolution.  Nevertheless, "similarities
between the dentition of the basal therizinosaur _Falcarius_ and the basal
oviraptorosaur _Incisivosaurus_, ... raises the possibility that the common
ancestor of these clades [Oviraptorosauria, Therizinosauroidea] had already
undertaken the initial steps in this transition."  But I wonder if this
transition might have begun even earlier, based on the dentition of troodontids
and the posterior shift of the pubic shaft that appears to be primitive for the
Maniraptora.>

  This is a very beautiful animal, and I was so happy to finally see it
presented in Denver last year for SVP. Kudos on a great and imaginitive name!
To note, though, it is my observation that "rootward" segnosaurs like
*Falcarius* and *Beipiaosaurus* possessed relatively mesopubic pelves, while
reversion was occuring in *Nothronychus* and *Alxasaurus*. Similar vertical
pubes occur in *Nomingia*, *Caudipteryx*, and apparently also in _some_ of the
oldest troodontids, such as *Sinornithoides* (whereas *Sinovenator* appears to
have a somewhat opisthopubic pelvis). It would be likely, therefore, that a
vertical pubis was the primitive condition for segnosaurs.

  Cheers,

Jaime A. Headden

  Little steps are often the hardest to take.  We are too used to making leaps 
in the face of adversity, that a simple skip is so hard to do.  We should all 
learn to walk soft, walk small, see the world around us rather than zoom by it.

"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)


                
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