Re: Did non-avian dinosaurs guard nests?

[John Bois <jbois@umd5.umd.edu>]

On Thu, 23 Oct 1997, Thomas R. Holtz, Jr. wrote:

> We can't "know" that it isn't convergent, just as we can't "know" that the
> feathers of crows are homologous to feathers in ravens (to pick an extreme
> example).  In evolutionary biology, similar derived features are assumed a
> priori to be homologuous, and the concordance of distribution of other data
> will support or reject an hypothesis of homology.  In this case, given the
> known distribution of this trait among living amniotes, it is more simply
> explained by a single evolutionary event (at the base of Archosauria) rather
> than two (once each for Crocodylia and for Aves) or more often (e.g., once
> for gavials, once for crocodylids, once for alligatorids, once for tinamous,
> once for ratites, once for neognaths).

This makes sense.  And thank you for such a lucid account of this
technique.