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There's no problem with saying that birds evolved from Saurischia - indeed,
by current nomenclature, they _are_ Saurischia :-).
Don't get the 'meaning' of a taxonomic name confused with it's
derivation. While derivation may _indicate_ intended meaning, the name of a
taxon generally doesn't change even if it is found to be inappropriately
derived. This saves us from having to coin and learn new names all the time.
So the fact that 'Saurischia' originally meant 'lizard-hipped' is completely
irrelevant even if it later turns out (as it did) that some animals with
bird-like hips should be included in it. Offhand, birds weren't the only
saurischians with bird-like rather than lizard-like hips - therizinosauroids
and at least some dromaeosaurids also developed them.
To give other examples of how inappropriate names remain stuck,
_Therizinosaurus cheloniformis_ ('turtle-form') keeps its name despite
turning out to look nothing like a turtle, Ornithopoda ('bird feet') and
Theropoda ('beast feet') remain in use despite the feet of the former not
being particularly bird-like and those of the latter not very mammal-like,
_Sarcolestes_ ('flesh robber') turned out to be a herbivore... I could go
on, but you get the picture.
On 24/5/05 3:02 pm, "Benjamin Hughes" <firstname.lastname@example.org> wrote:
> I'm sure this is a simple question, but one that has puzzled me for some
> time, I cannot find any simple answer.
> If we can easily divide Dinosaurs into Saurischia (lizard-hipped) and
> Ornithischia (bird-hipped), is there a problem with stating that birds have
> evolved from the Saurischian Therapods?
> I don't doubt myself that the two groups are related, but perhaps the birds
> evolved in the early Triassic as well, and from there there has been a lot
> of cases of parralel evolution.
> If not, at what point did birds change from being Saurischians to
> I don't have access to scientific journals, I wish I did. Instead I have
> this mailing list :-)
> The Australian Discworld Convention - www.ausdwcon.org