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Re: Dinosaurian Class
> It's: Amniota including Diapsida (crocs, dinos, birds, lizards) and
>Synapsida (pelycosaurs, us) with the outgroup as Anapsida (your
>favorite box turtle, for instance).
This classification has now fallen out of favour. It is more likely that
Chelonians are Diapsids which secondarily reverted to the anapsid state
(their skulls are clearly heavily modified). Other anapsids are a
paraphyletic mix of early Amniotes.
I do not know the difference between Reptilia (new definition) and Diapsida.
>>Does this mean we're all bacteria?<g>
> Bacteria exist on a different branch of the tree of life than do any
>other form of life, extant or extinct. The Tree of Life page has this,
>and so does Mike Keesey's Page.
I can't comment on either web site right now, but the first statement is
definitely wrong. eubacteria unquestionably share more recent common
ancestors with Eukaryota than with archaebacteria/Archaea.
> Pretty much, we are derived from the most recent common ancestor of
>bacteria and all other life, with bacteria as the outgroup. This is to
>say, we are derived from a bacteria-like creature that is not,
>essentially, bacteria. Same for dinos, birds, etc.
Eukaryotes are (descended from) a symbiotic aggregation of at least two
bacteria. The cytoplasm+nucleus and the mitochondeia of a Eukaryotic cell
are (descended from) different bacteria. Some argue that microtubule
organising centres were/are another. Chloroplasts, where present, are yet
Cladistic assumptions break down when dealing with bacteria, especially
eubacteria, because of horizontal gene transfers. The same goes for
viruses, if they are to be included at all. bacteria should be separated
for this reason, and not because they form a clade.
N.B. In the above, clades begin with a capital letter, grades lowercase.
All the best,