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Re: Removing segnosaurs from Theropoda
>From: email@example.com (Jason Head)
> > In addition,
> >how does one use the indentary plates of "thecodontia" to resolve
> >dinosaurian systematics, when the plates appear and disappear throughout
> >the various lineages so paraphyletically defined? Which member of the
> >thecodonts will you use for your outgroup(s): aetosaurs? riojasuchids?
In constructung a cladogram I do not use paraphyletic groups.
In fact I prefer not to use groups at all - just individual species.
> > Using paraphyletic groups in fine for paleontology in
> >situations where you want to discuss a lineage of critters, w/ out
> >involving their DIRECT descendants. That was the crux of my posting a few
> >weeks back.
They are also useful for defining cohesive, maximally similar groups
among living forms.
> > What, besides Triassic extinctions, can be discussed about
> >thecodonts, that doesn't also imply dinos', pterosaurs, and crocs'? If
> >you want to snip birds off of the dino' tree to talk about the big, dead
> >fellas, fine- but to snip dinos' pteros' AND crocs' off of archosauria (ne
> >"thecodontia")? What information will that give you?
Potentially lot. Try reading chapters 9 & 10 of Mayr and Ashlock, 1991
(I think that's the year) - _Principles of Systematic Zoology, 2nd Ed._.
Or even better, read Kent Carpenter, 1993 in Syst. Biol. 42(2),
The only point I will admit here is that I have not yet performed an
actual informaion content analysis of the division I proposed. It
is possible that when this becomes possible, I will revise my
In general, however, the thecodontians are a collection of quadrupedal,
semi-erect archosaurians with no special locomotory adaptations.
[Hmm, on this basis, Olshevsky's inclusion of the crocodylians there
may be appropriate].
The peace of God be with you.