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Re: [Combined answer: Feathered/scaly theropods: trying to make the point.]

At 07:52 AM 26/06/01 -0400, philidor11 wrote:
It's possible to disagree with each of the following statements:
First, all animals with feathers are closely related.
Second, if one or more of a group of closely related animals have feathers,
then all other animals in the group had feathers.  (This assumes it is
possible to determine conclusively that the animals are closely related by
ancestry, using characters not limited to feathers.)

One difficulty with being too solidfirm on this point is that we really only know of a very few dinosaurs with definite feathers, as opposed to integumentary structures that might well be feather homologues but have not been conclusively proven to be so. The structures in (say) Sinosauropteryx could just possibly be analogous to feathers rather than homologous with them (as are, I presume, the "hairs" of pterosaurs), in which case we really can say very little about the integument of all the animals in the clade containing both Sinosauropteryx and birds beyond noting a tendency within the group to evolve a hairlike or featherlike covering.

Mind you, I think assuming that the Sinosauropteryx structures are feather homologues is a reasonable working hypothesis - but (unless I am much mistaken) it is, pending further evidence from microstructure, no more than that.

Ronald I. Orenstein Phone: (905) 820-7886
International Wildlife Coalition Fax/Modem: (905) 569-0116
1825 Shady Creek Court
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