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Re: New alvarezsaurid
>Not if one of those theropods were to inhabit a niche not explored by
>its competitors, and later specializied because of the lack of
>competition, it would occlude any unneccesary features that did not
>maximize the performance in said niche. The kiwi, for instance, lays
>huge egg, as the two ovaries, whatever (this does not mean it is
>suddenly so wierd it _can't_ be a ratite, all others of which lay more
>than one egg) to increase survival statistics, is small and fast and
>thus can dodge predators two ways, is colored for camouflage, and the
>bill is especially derived from other ratities and tinamous.
Yes, but it still has the paleognathus palate and other ratite
characteristics in the hyoid, inner ear, etc. It still has all of the
derived characteristics of its ancestors, it did not lose two dozen some
features. Oviraptors and alvarezsaurs do not share any major characters.
>Owls are exclusive predators (I'll take *Bubo bubo*, the eagle owl) and
>so are goatsuckers, but owls have feet with the fourth digit reversed,
>in the manner of woodpeckers. This does not make them woodpeckers. They
>developed features, lost them, and became unique, but their still,
>esentially, derived goatsuckers (or goatsuckers are derived owls).
There are major instances of convergence in Aves, such as the
repeated developement of the zygodactylus foot, but these features do
not mean relateness. I think that the two major schemes of bird
evolution ( Martin : Sauriurae, Ornithurae . And Chiappe:
Ornithothoraces) still provide better examples of how birds evolved.
Using both schemes you can tell what is a convergence or what is not.
Relationships cannot be derived from one or two ambiguous characters,
but in basic osteology, myology, life histories, behaviors, and DNA.
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