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Re: Archie the Dinosaur?



In a message dated 95-12-04 11:55:16 EST, Thomas_R_HOLTZ@umail.umd.edu (th81)
writes:

>In phylogenetic taxonomy, once you are a member of the taxon, your
>descendants will ALWAYS be a member of the taxon, no matter how derived they
>become.  Trochilids (humingbirds) are birds, and maniraptorans, and
>coelurosaurs, and avetheropods, and tetanurines, and theropods, and
>saurischians, and dinosaurs.

This presumes that the only admissible taxa are clades. It is certainly true
that once you are a member of a clade, your descendants will always be
members of that clade; but it is dogmatic to insist that all taxa be clades.
Hummingbirds are (probably) dinosaurs only cladistically, not necessarily
taxonomically.

Also, your cladistic hierarchy is open to question, by me at any rate. People
have been objecting from time to time about the lack of qualifiers in my
discourse and about the positiveness with which I make some of my statements.
Well, this objection applies equally to your statement that hummingbirds are
birds, and maniraptorans, and so forth. We know that hummingbirds are birds,
but the statement that birds are maniraptorans (for example) is not as secure
and depends on cladistic analysis whose correctness cannot be completely
established no matter how many computers are used and how many professional
paleontologists think it can. (Although even I happen to think it's probably
correct.) By the time we work up to Saurischia in the hierarchy, my own
analysis (as well as that of a couple other paleontologists) indicates it is
a paraphyletic group diagnosed by a combination of plesiomorphies and
homoplasies.

It's time for the Happy Hunting Ground for Saurischia, as a clade, anyway.