Re: synapsids are reptiles

["T. Michael Keesey" <mightyodinn@yahoo.com>]

--- Steve  Brusatte <dinoland@lycos.com> wrote:

> >  > The situation in amniote phylogeny is so fluid that perhaps is better, 
> > at least for the 
> > > moment, to maintain in use the traditional distinction: 
> > > synapsida-diapsida-anapsida, > > >
all  inside the Reptilia.
>
> > You do know that by your suggestion you are a reptile, and Reptilia becomes
> > the same as Amniota? :-)
> 
> Yup, the precise problem in resorting to the synapsid-diapsid-anapsid
> classification.  I don't like it for the reason David mentioned.

_Synapsida_, _Diapsida_, and _Anapsida_ are still used. And why rename 
_Amniota_ to _Reptilia_? Or
am I misunderstanding?

> The situation in amniote phylogeny is so solid that perhaps it is better to
> abandon the term Reptilia altogether. We have beautiful, precise terms like
> Amniota and Sauropsida, let's use them instead. If only because they don't
> carry connotations like "low vertebrate", "cold-blooded", "sluggish" etc.
> etc.. :-)

_Reptilia_ names a different clade than _Amniota_ or _Sauropsida_ (although it 
currently has the
same content as _Sauropsida_). I wouldn't mind changing the name myself, but 
the clade (crown
clade anchored on testudines, lepidosaurs, and crocodylians) still should have 
a name.

Ken Kinman wrote:
>   I would agree with most of what Alberto said.  I would only add that 
>    since turtles are probably diapsids which reversed back into an anapsid 
>    condition, defining Reptilia as a clade was a very bad idea in the first 
>    place (and for other reasons as well, as has been often pointed out).

*IF* turtles do turn out to be within the Lepidosauria + Archosauria clade, 
that doesn't mean
naming _Reptilia_ was a bad idea. It just becomes a heterodefinitional 
(=subjective) synonym of
_Sauria_. (Not sure which should have priority, though.)

back to Steve Brusatte:
> How many published analyses support the turtle-diapsid linkage?  I know of
> Rieppel's Nature paper published a few years back, but, IIRC, the hypothesis
> of turtles as diapsids is far from certain.

That was my impression as well.

> >An Order Diadectiformes as the 
>    basal clade of Class Reptilia seems the best current option and predict
> that 
>    it will remain in that position (thus promoting stability).
> 
> Hmmm...I don't know how stable this would be.

Yeah, you can "predict" anything to be stable in terms of content. True 
stability can only be
guaranteed for definition, the only part we have complete control over.

=====
=====> T. Michael Keesey <keesey@bigfoot.com>
=====> The Dinosauricon <http://dinosauricon.com>
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