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Re: questions about the Odontochelys study

Mike Keesey wrote:

> > And I don't recommend making such a name up just
> yet :-)
> Why not, as long as the definition collapses should
> archosaurs prove
> to be descended from the final common ancestor of
> testudines and lepidosaurs?

I agree.  Including the right negative/external specifiers in each definition 
would ensure that a Testudinata-Archosauria clade and a 
Testudinata-Lepidosauria clade were mutually exclusive.  The respective 
definitions would ensure that only one (at most) could be used in any topology. 
 This allows a given name to be explicitly linked to a specific phylogenetic 
hypothesis (turtles closer to archosaurs than to lepidosaursm or vice versa).

For example, if a Testudinata-Archosauria clade (let's call it 'Chelarchia') 
was defined as the least inclusive clade that includes turtles and birds, but 
not lizards, and a Testudinata-Lepidosauria clade ('Chelolepida') was defined 
as the least inclusive clade to include turtles and lizards, but not birds, 
then if the former clade was recovered, then Chelolepida would collapse 

If turtles (Testudinata) were recovered as outside the Archosauria+Lepidosauria 
clade (a third phylogenetic hypothesis), then neither name is viable.