From: Mike Taylor <mike@indexdata.com>
Pretty much all you _can_ say with any certainty is that
_Archaeopteryx_ is a bird -- because it's one by definition. The
standard definiton of Aves is {_Archaeopteryx_ + Neornithes}, that is,
the most recent common ancestor of _Archaeopteryx_ and common birds,
plus all its descendants. So (asusming you use this definition -- not
everyone does), Archie is a bird; but what else is? It depends on how
the phylogeny falls out. For example, if it looks like this:
+-- Carnosaurs
+-- _Deinonychus_
+-- _Archaeopteryx_
+-- Modern birds
Then _Deinonychus_ is not a bird; but if it looks like this:
+-- Carnosaurs
+-- _Archaeopteryx_
+-- _Deinonychus_
+-- Modern birds
Then _Deinonychus_ _is_ a bird.