Re: Mesozoic-ware

[pharrinj@PLU.edu]

On Sat, 13 Jan 1996, Jeff Poling wrote:

> >>    I use the clade version.  I'm not sure what the demarcation is ... I
> >> suspect it isn't amniote minus synapsid as that would include amphibians 
> >> ...
> >
> >Amphibians are tetrapods but not amniotes.  Amniotes are those tetrapods 
> >that lay shelled eggs (or, for you more strict cladists, all descendants 
> >of the last common ancestor of, say, me and a hoatzin).
> 
>    I'm still in the process of switching from Linneanism to cladistics.  As
> I recall, amniotes are characterized by an egg with a fluid filled
> (amniotic) sack.  Would this not, then, include amphibians?  I am assuming
> that the choice of "amniota" in cladistics has a similar connotation, even
> though it's based on descent rather than physical characteristics.
> 

No, really, Amniota is tetrapods minus amphibians, or all descendants of 
the common ancestor of mammals and birds (or lizards, or turtles, etc.).

    Nick