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Reptilia; dispelling "delusions"
Why not treat both living and extinct animals the same? Why differentiate
I agree for the most part. We can't really treat them "exactly" the
same, but both living and extinct groups should obviously be integrated into
a single classification (and treated the same to the degree that the
evidence will allow). Therefore, I don't like crown group definitions for
taxa, because they *do* over-emphasize the living groups. "Living" vs.
"extinct" is clearly a lousy character distinction (and phylogenetic
"anchoring" definitions in general unfortunately use taxa rather than
characters---now that's what I call arbitrary).
In vertebrates, osteological characters obviously give us the best way
to classify overall. That is why scientists have long characterized
Mammalia using the transformation of certain jaw bones into the three ear
ossicles (rather than using hair or endothermy, or anything else the fossil
record rarely preserves). I would like to see that same thing happen to
Aves---based on osteology (not a crown group or phylogenetically anchored).
THIS all brings us to the Reptilia problem that is also being
discussed on the list today. However one defines Mammalia and Aves, the
traditional Reptilia is simply all basal amniotes excluding the two exgroups
Mammalia and Aves. Reptilia have a common ancestor (first amniote), so
although excluding two exgroups is admittedly arbitrary, it is still
natural, useful, and has a long tradition as well. The really dumb thing
about traditional classifications is that they often fail to explicitly
label such paraphyletic groups as such (and should include markers for the
exgroups, as Benton has begun doing). Anyway, the traditional synapsids
(pelycosaurs and therapsids) are simply the "mammal-like" reptiles which had
not yet evolved the mammalian jaw and ear ossicles.
If only we had such an osteological character complex which clearly
distinguished birds (incl. dromaeosaurs and various other traditional
theropods) from the "bird-like reptiles" (i.e. "primitive" theropods). In
my opinion that would be the most effective way to battle Feduccia's BAND
crusade. It would also free us from the blurry distinction which
Archaeopteryx has slowly forced upon us (i.e., regarding it as the first
bird has outlived it usefulness and has become a liability instead).
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