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Re: (Hopefully not much more) cladobabble



In a message dated 97-11-21 02:36:21 EST, th81@umail.umd.edu writes:

<< Sure, nobody can confuse a _Triceratops_ and a
 hummingbird, but the morphological distance between a small dromaeosaurid
 and _Archaeopteryx_ is VERY tiny.  As bird origins become better known, the
 supposed great morphological gap between birds and non-birds is very, very
 hard to find. >>

Actually, the biggest morphological gap lies between _Archaeopteryx_ and
other birds.

Speaking of which, we should explore the consequences for dinosaur-bird
taxonomy >if< the recent paper in _Science_ on the numbering of the modern
avian wing digits is II-IV rather than I-III is >true<. It would mean, for
example, that modern birds lie on a different branch of the dinosaur family
tree than _Archaeopteryx_, dromaeosaurids, and most if not all known
theropods. But since both _Archaeopteryx_ and modern birds are feathered
fliers, it would also mean that the common ancestor of both branches was
feathered (unless identical feathers appeared convergently--not bloody
likely) and was likely capable of flight. So feathers and some kind of flying
capability might have already been around in the Late Triassic among small,
arboreal or acronomic dinosaurs. (Where have we heard this before?) The
_Science_ article could also provide an explanation for some of the puzzling
differences between enantiornithan birds and modern birds (e.g., the furcula
shape, the conformation of the pectoral bones), if we recognize the e-birds
as those having wing digits I-III and modern birds as those having wing
digits II-IV.

I won't even mention the terrible flaw this would expose in cladistics: the
deleterious effect of massive convergence in closely related lineages on a
cladistic phylogeny.