Re: Lewisuchus, a Dinosauriform

[Dinogeorge@aol.com]

In a message dated 7/23/01 2:15:32 PM EST, Mickey_Mortimer11@msn.com writes:

<< And why do you place so much emphasis on phalanx V-1, at the expense of
 letting over twenty other characters reverse or parallel?  Do you have other
 characters to support your phylogeny? >>

Loss of a digit has proved to be, I believe, pretty much irreversible among
dinosaurs. So it should have a very strong weight in phyletic analysis. My
method is to isolate a lineage that displays a simple trend or two, then see
what happens after you hang the other clades off the lineage according to the
trend(s). In BCF, I took the lineage from a presumed ancestral archosaur to
modern birds and hung the various archosaur and dinosaur clades off it--and
arrived at pretty much the phylogeny you exhibited in your post. Note that a
trend is an artifact of isolating a lineage: isolating the lineage comes
first, then seeing what trends appear in it. The side branches off the main
lineage represent lineages in which the trends may or may not have continued,
or may even have reversed--or in which new trends appeared.

In the BCF lineage, the trends in the feet are to lose the fifth digit, then
to bring the first digit into opposition with the other three digits. The
trends in the forelimb are to lose the outer digits in serial order, then to
become a foldable wing. The trends in the skull are to lose the teeth and to
enlarge the braincase. The trend in the hind limb is to become erect, with
the joints becoming progressively more fore-and-aft-directed. And so on.