Re: Ornithischian clavicles

["Nick Gardner" <ratites637@hotmail.com>]

Richard Butler wrote:
> However how is it possible to be certain that the absence of ossified
> clavicles in ceratopsids is not just a preservational feature as well? I
> assume that they have been coded as absent based on the fact that many of
> the ceratopsid taxa are known from very complete material. If this is the
> case should it not be possible to code them as absent for other very well
> known taxa such as Iguanodon and Hypsilophodon? The phylogenetic bracket
> would then imply absence of ossified clavicles as the basal condition for
> Neornithischia at least and probably for Ornithischia (clavicles are 
> unknown
> in Thyreophora). Thus presence of ossified clavicles would be a 
> synapomorphy
> of a clade including Psittacosaurus, Protoceratops, Leptoceratops and
> Montanoceratops (i.e. Ceratopsia), regardless of the fact that derived
> members of that clade, the Ceratopsidae, then reverse the condition.

There is no reason why if all of the above are true, that it could not be a 
synapomorphy of such a clade, I simply meant that it was not likely to 
support a clade in which these taxa are included to the exclusion of 
ceratopsids.  Has anyone ever suggested that anyway?  I know that 
_Protoceratops_, _Leptoceratops_, and _Montanoceratops_ have probably all be 
grouped together in the Protoceratopsidae at one point or another.

Nick Gardner

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