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Re: Saltopus... a silesaurid?



On Thu, May 19, 2011 at 11:50 PM, Augusto Haro <augustoharo@gmail.com> wrote:

> According to a Figure in Sereno 1991 (Memoir of the SVP) on the tarsus
> of a phytosaur, it was apparent that the "astragalar peg" was scarcely
> developed, the astragalo-calcaneal articulation being not much
> different from the common basal archosauriform condition. So,
> considering phytosaurs as crocodile-normal is partially a "courtesy"
> with them (as would have say Romer).


Well said.  Further, as you know, the "crocodile-normal ankle" is an
assemblage of characters, rather than a discrete character.  Sort of
like the "perching foot" of birds.


Nevertheless, phytosaurs were traditionally included in the clade
Crurotarsi, because Crurotarsi was usually defined to include
phytosaurs.  Using Nesbitt's definition, phytosaurs are members of the
Crurotarsi given that he uses _Rutidon_ as an internal specifier.  So
with his new tree recovering phytosaurs as the sister group to
archosaurs, we have non-crurotarsan (the condition) members of the
Crurotarsi (the clade).  I think it would have been preferable to
re-define Crurotarsi such that it excludes those archosaurs on the
bird-line  - such as having a bird species as a negative external
specifier.



Cheers

Tim