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Re: another dumb question: Terror Birds are not dinosaurs?
Anything that is derived from the most recent common ancestor of
_Archaeopteryx lithographica_ and _Passer domesticus_ is regarded as a
bird (Aves). (There are few other definitions too...)
If it is derived from the most recent common ancestor of _Triceratops
horridus_ and _Megalosaurus bucklandii_ it is classified as a dinosaur
(so any bird is a dinosaur too - from the fact that they are derived
from that ancestor).
If a critter is derived from the most recent common ancestor of _T.
horridus_ and _M. bucklandii_ but not from the most recent common
ancestor of _A. lithographica_ and _P. domesticus_ than it is
informally called a non-avian dinosaur, that is commonly called simply
as a dinosaur.
How do we know that an organism if derived from such common ancestor?
By an analysis of characters called philogenetic analysis or
cladistics - it group together organisms that share some exclusive
On 6/29/07, Paula Goodman <firstname.lastname@example.org> wrote:
With all this talk about birds-are-dinosaurs, I'm curious to know what,
if anything, distinguishes the bird status of Phorusrhacidae from that
of the recently discovered Gigantoraptor, for example. Why do we call
one a big bird fossil, and the other a dinosaur fossil?