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Re: T-J Extinction event article (more media errors?)
<<This problem can be nipped in the bud (as it were): Don't have
George Olshevsky (Dinogeorge@aol.com) wrote:
<The reason to have paraphyletic taxa is to avoid having 2n
higher taxa for every n species. Consider: no matter where you
add a species to a cladogram, you add another node to it, and
thus two more potential supraspecific taxa to your taxonomy (one
node-based and one stem-based). Who needs so many taxa?>
Yes, indeed. I abhor excessive node-naming. This is a
ridiculous practice. There are, in some cases, groups for which
it is preferrable to have names applied (Archosauria, Aves,
etc.) that help in forming reference to living taxa and their
relationships. To be plain, most taxa are based on a series of
nest crown-groups, to which fossil taxa are applied and stemmed.
So if there's a fossil group to which [n = >10] taxa or so are
grouped into, then that can perhaps have a placement to extant
taxa in the sense that a node is named. For those with much more
taxa [n = >500] then a host of internal nodes would be needed.
So it is useful to distinguish between club-tailed and unclubbed
ankylosaurs, or sauropods with no thumb claws, etc. For
instances where it is supremely suitable to name groups for
which claritive purposes are desired, as in broad-jawed
tyrannosaurs vs. narrow-jawed tyrannosaurs, then a name can be
coined for which specific workers can refer to. This is as in
specialties. No one suggest we regularly refer to subgroups of
club-mosses regularly, when we study vertebrates, so that in
each of our specialties it is desirable to have a field of
continuing clarity we can work in.
<(And I won't even go into the problems that >incorrect
placement< of a species could generate.)>
Oh, yes ... this can be horrendous. Remember titanosaur
systematics in 1990 and before were wacko, and we still can't
seem to see what makes Ornithomimoidea a better placement in the
strict sense than Metornithes in the strict sense.... Should we
give up? No, more work; that old Buddhist proverb applies about
chopping wood before and after enlightenment.
<Better to group the multitude of clades into a simple,
partitioned hierarchy of larger groups that aid in general
This hierarchy, as in atomic research, gets more refined and
varied the closer we look. We find a simple hierarchy is
composed of many simple hierarchies, and so on. Down to
individuals. Those who deal with the finer hierarchies find they
need the finer clarification and reference terms to communicate.
Those who work generally do not neccesarily need them.
Jaime A. Headden
Where the Wind Comes Sweeping Down the Pampas!!!!
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