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Re: Re: Warm Blooded vs. Cold Blooded



>        Ectothermy is the primitive condition in reptiles.  W/out evidence
>to support the evolution of the derived condition (endothermy), the
>primitive condition is assumed.
>
This isn't quite using the extant phylogenetic bracketing method.  The
extant ingroup, birds, are all endothermic.  As for outgroups, crocodiles
are ectothermic, lepidosaurs are ectothermic, turtles are ectothermic, and
mammals are endothermic.  As such, assuming either endothermy or ectothermy
by phylogeny, rather than other evidence, is very weak.

Thomas R. Holtz, Jr.
Vertebrate Paleontologist
Dept. of Geology
University of Maryland
College Park, MD  20742
Email:Thomas_R_HOLTZ@umail.umd.edu (th81)
Fax: 301-314-9661
Phone:301-405-4084