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Re: Re: Dino/bird reply



>> 
>> "A bird" never stopped being "a dinosaur." Birds are a group nested within
>> the Dinosauria.  You never stopped being an animal, a tetrapod, a synapsid,
a
>> mammal, a primate or a hominid, just because you happen to be a human.  
>
>    We stopped being insectivores, reptiles, and fish.

"Fish" is a paraphyletic term.  We remain vertebrates (fish = all verts
which are not tetrapods).

We never were insectivores in the sense of "Liptophyla" (sp?), i.e., the
shrews, hedgehogs, etc.  Mammalogists have long recognized that these
insectivores may be "primitive" in some senses, but are not the stem group
from which all other mammalian stocks evolved, H.F. Osborn notwithstanding!

We never were reptiles.  The basal synapsids (so-called "Mammal-like
reptiles") are excluded from a monophyletic Reptilia (see below) and
probably lacked the vast number of hard- and soft-tissue synapomorphies
uniting Reptilia.  We remain amniotes, though.

True monophyletic Reptilia in current usage is defined as "the most recent
common ancestor of turtles, lepidosaurs, and archosaurs, and all of that
ancestor's descendants".  All taxa closer to Reptilia than to Mammalia are
members of Sauropsida.

(Incidentally, we remain members of the sister taxon to Sauropsida, namely
Synapsida).

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