[Taxacom] What taxon corresponds to "birds'?

Kenneth Kinman kinman at hotmail.com
Mon Nov 28 22:44:47 CST 2016

Hi All,
       For thousands of years (or longer), there has long been a classificatory distinction between reptiles and birds, although Archaeopteryx eventually showed that birds are clearly reptile descendants.  This was reflected in both informal and formal classifications as Classes Reptilia and Aves.  But the more recent discovery of fossil intermediates has blurred where to draw the line between reptiles and birds.  And around the same time we had adherents of phylogenetic nomenclature  concluding that both paraphyly and ranked classifications are somehow "unnatural".  And yet decades later the PhyloCode is still extremely controversial and perhaps not likely to be implemented anytime soon (if ever).
       In the meantime, even among strict cladists, the meaning or definition of Class Aves has become increasingly muddled, between those who would make it a crown group (and thus a synonym of Neornithes) or alternately based on a group including Archaeopteryx, crown-group birds, and all of their descendants.
       Given this muddled situation, I have long favored expanding that Class (for birds) to include avian dinosaurs that seem to have preceded the common ancestor of Archaeopteryx and modern birds.  Given the importance of flight in the concept of "birds", I have come to the conclusion that asymmetical flight feathers are a primary evolutionary development in what constitutes a "bird".
       Therefore, given the muddled debate whether Aves is the crown group or anchored instead on Archaeopteryx, I would perhaps suggest that we recognize a Class Paraves for "birds" rather than a Class Aves.  The discovery of Archaeopteryx long before all the other intermediates between reptiles and modern birds long made it a convenient anchor for a very long time, but it no longer seems to be so important given all the other forms since discovered (some older) with adaptations for flight (the asymmetic flight feather being a primary synamorphy, although even though its gradual developmental can be problematic given problems inherent in fossil specimens).
       Therefore, should we start calling it Class Paraves, or expand Class Aves to become a synonym of Paraves.  I'm not sure which would be the best choice.  However, I am convinced that we need to expand the concept of "birds" as a Class separate from Class Reptilia.  Whether we call that Class Paraves or an expanded Class Aves is the question.

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