Re: Arbitrary Paleontology

["Jonathan R. Wagner" <znc14@TTACS.TTU.EDU>]

W. J. T. Mitchell wrote:
>I gather that everyone (everyone?) now believes that this problem has been left
>behind, and that dinosaurs had a common ancestor.
        Time for my bi-monthly chime-in:
        The odds that all dinosaurs had a common ancestor are probably
astronomically huge. To demonstrate that they did not involves demonstrating
the independant evolution of two (or more) unique separate lineages of life
from the "primordial soup", up to and including a demonstration of how all
dinosaurs share such bones, or for that matter exactly how both lineages
evolved bones which appear to be of the same general chemistry and structure.
        So, allow me to rephrase for you:
"I gather that everyone (everyone?) now believes that this problem has been left
behind, and that dinosaurs had a common ancestor which is included within
the Dinosauria."
        The answer appears to be yes: traditional taxonomists (such as
Bakker and, I believe it was Galton) have accepted this, and phylogenetic
taxonomists accept a DEFINITION of Dinosauria which necessitates it,
although different formulations of that definition may exclude some taxa
traditionally considered dinosaurian (e.g. _Herrerasaurus_) or include some
not traditionally considered part of the group (e.g. birds).

        Hope this helps,

        Wagner
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     Jonathan R. Wagner, Dept. of Geosciences, TTU, Lubbock, TX 79409-1053
 "Only those whose life is short can truly believe that love is forever"-Lorien