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_Requiescat In Pace_
I guess this should be my final stint on this thread.
Cladistic phylogeny seeks to group all descendants of a single answer
since paraphyly is only relative and seeks to isolated certain basal
features by excluding a lineage or two. That is part of the intent
anyway. What seems to be the problem is that there is a perception,
perhaps, that cladistics ignores paraphyletic taxa since it explicitly
does not include them, when in fact a paraphyletic taxon cannot exist
because -- and anyone jump on me here -- you have to select more than
just a lineage to exclude (Tetrapoda out of Gnathostomata) but its
temporality as well to isolate a taxon. "Fish" is valid as a "taxon" as
long as there are no tetrapods to worry about, then such a "taxon" can
be inferred. Then its just a monophyletic [holophyletic] group whose
land-lubbering lineage has yet to evolve. Fine. Temporality is the key.
I agree with Ken and George on the matter of selecting a definition of
a group as a paraphyletic taxon, but this taxon is only real so long as
it lacks lineages which are being excluded. A paraphyletic group [note:
the taxon as a formal entity is what I'm arguing against] is only valid
in relation to a lineage, not in an absence of one, because one is
reflecting on the basal, "primitive" morphology reflected in "fish" as
relative to tetrapods.
People were fine thinking birds weren't dinosaurs because they were
warm-blooded, reptiles were not, dinosaurs were reptiles, and reptiles
were cold-blooded. In an absolute Golden Ladder rule. Along comes
*Archaeopteryx* and Huxley and Darwin, and people start seeing birds as
descendant of theropod dinosaurs. The arguments made in the 1800's
however, reflected the geological and fossil record -- poor, at least
as relative to the present era of discovery, and much of Marsh's and
Cope's and Dong's and Janensch's discoveries and analyses by them and
Huene, etc.. Now we try to better formulate our hypotheses. The studies
have become richer as a result. Now we see that *Archaeopteryx* is only
a step between *Mononykus* (say) and *Confuciusornis.* There's nothing
really special about it, besides being the catalyst in this debate.
There's nothing really special about tetrapods, fish, birds, dinosaurs
[sorry, everyone but Chris], crocodiles [sorry, Chris], and so on. They
are constantly shifting paradigms, as we know them, but the whole
phylogeny, as ideally construed, will have every morphology between two
organisms who _are_ descendant of each other, for there to be a
"missing link" so to speak. There are no lines, there are no boxes,
rungs, ladders, ranks, markers. Just forms on the way through life,
having abilities which may or may not be suited to their environment,
evolution, etc. Defining groups by what we percieve as end taxa
requires all the end taxa stemming from a common ancestor (at least as
far is known), not some of them. One ignores the whole by excluding a
lineage. One ignores the lineage between *Eoraptor* and *Archaeopteryx*
by removing *Archaeopteryx* and thus by so doing are saying that
[bearing in mind that birds are defined as the most recent common
ancestor of Archie and living birds] the form that preceeds Archie in
the fossil record (perhaps *Jurapteryx*/Eichtaett specimen? or
whatever) has no evolutionary basis but yet another marker, yet another
paraphyletic group to recognize. Then there's the morphology preceeding
_that_. And the one before _that_, going down the line past all the
forms including dromaeosaurs, oviraptorosaurs, ornithomimosaurs,
tyrannosaurs, compsognaths and coelurids or wherever those last go,
allosaurs, abelisaurs and ceratosaurs, coelophysoids, herrerasaurs,
staurikosaurs, and all the forms between _them_, each being a
paraphyletic group. With a significant, earth-shattering morphology.
I mean, for crying out loud, resurgence of _claws_ in *Opisthocomus*
has _got_ to have a remarkable evolutionary and taxonomic significance,
right? That's what the orignal analysts thought. Or what about the
incredible syrynx [_major_ evolutionary novelty, new superorder!] or
the reflexed perching foot [even better, superspecialization!
Definitely a superorder!] Or whatever a superorder is.
Or in other words: what is the difference between "Aves" and "Class
Aves"? Evolutionary context. Phylogenetic assumption that novelty, like
the rostral bone that Tom pointed out, should in some way signify
higher rank, and the inevitable marker or its equivalent in a
phylogenetic scenario. Does then any novel bone qualify for a higher
rank than one's predecessors?
And I can tell you about some of those birdy novelties, they are not
novelties; there is a tendency to regard a scheme, and if
well-responded to in the past, as the "Class Aves/Class Reptilia"
paradigm, to carry it forward in spite of the recognition of infinite
transitions. There are no lines, boxes, ranks....
My last post on the thread....
"There is no spoon."
Jaime A. Headden
Where the Wind Comes Sweeping Down the Pampas!!!!
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