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From: Tom Holtz <email@example.com>
> I wrote:
> >So it's therapods, carnosaurs, sinraptors
> >or therapods, carnosaurs, maniraptors?
> >(Perhaps instead of requesting books for my son, I should ask for some
> >for myself ;^))
> Actually, "Carnosauria" doesn't seem to be a natural group (a group with a
> common ancestor and all of its descendants).
Well, some people would say the only necessary criterion for
a group to be natural is the first. And it still seems likely
that that is the case.
Thus, this is a matter of personal taste. Either approach is
valid in one model of taxonomy.
> >Finally, last week I asked about name changes (and received several
> >examples)--here's another one Gorgosaurus is now Albertasaurus?
> Actually, Gorgosaurus may NOT be Albertosaurus, since the features used to
> put G. libratus into Albertosaurus may simply be primitive features of
This comes down to the same issue. If one is willing to accept
taxa that do not include *all* descendents of the common ancestor,
then this is not sufficient cause to seperate Albertosaurus and
Gorgosaurus. Indeed, the tendency to this sort of fine splitting,
with lots of little teeny, isolated groups, is *one* of the reasons
I do not like the cladistic requirement for a taxon.
Now, this is not to say that the merger of Gorgosaurus and
Albertosaurus is appropriate either! If they are as distinct
as other members of Tyrannosauridae, then they should probably
be kept seperate.
The peace of God be with you.