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Re: bats & battalions (was Benton and Kinman)
David Marjanovic wrote:
Exactly how much morphological diversity is required? And _how_ do you
measure it? Or do you just _feel_ (aka _know_) what a class is
This is *exactly* the point I was making.
So be it, to eternity, amen? While Catenulida has been raised from order to
class status (not accepted by those who want to retain Turbellaria at any
price)?
This is certainly a can of worms (no pun intended). But there are further
examples which highlight the idiocy of arbitrary ranks. Should the
Tardigrada ("water bears") be considered a separate phylum, or a class
within the Arthropoda? Should the Pentastomida ("tongue worms") be regarded
as a separate phylum, or should they be considered an order within the class
Crustacea? Should the deep-sea-living Vestimentifera be put inside the
phylum Pogonophora, or outside as their own phylum?
Answer: Who cares?
What *is* important is the positions of Tardigrada and Pentastomida and
Vestimentifera within the phylogeny of metazoans. Do we have to waste our
time pondering: "Gosh, my research indicates that pentastomids evolved
within the Crustacea. But are pentastomids *different* enough to be
considered a separate class from the Crutacea? Hmmm..."
Further, if we discover a creature that seems intermediate between
pentastomids and another crustacean group, do we have to waste even more of
our time thinking: "Should I put this transitional critter in Class
Crustacea or Class Pentastomida? I shall be tossing and turning all night
deciding which class this new taxon should belong to!"
Ditto for _Archaeopteryx_, _Rahonavis_, _Unenlagia_ etc etc at the
non-Aves/Aves interface.
It was certainly not YOUR arbitrary idea. It certainly was an ARBITRARY
idea.
Ya got that right.
...some would invoke laziness of thinking for a reason, maybe. Tradition.
It
certainly works, but does it really work well?
Ken is using a circular argument: keep the tradition going because it's
traditional.
Tim
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