follow up on paraphyly / polyphyly

Ken Kinman kinman2 at YAHOO.COM
Wed Nov 10 19:19:36 CST 2004


Just a quick note on teaching about paraphyly.  I would definitely introduce the students to the concept of "exgroups".  The removal of these exgroups (like birds) is what renders the mother group (like dinosaurs) paraphyletic.

     Of course, if you leave a {{Kinman marker}} for the exgroup within the mother group, you don't lose that valuable information (the group is incomplete, but the information is not).  Paraphyly is certainly bad if it is not explicitly labelled as such.
             ---- Ken Kinman
P.S.  By the way, you might also want to mention that monophyly in pre-cladistic literature actually refers to holophyly + paraphyly (and if they run into the term holophyly, they will know what it means, i.e. holophyly = strictly cladistic monophyly).  Of course, then someone might ask why we don't use the term holophyly a lot more (and the only reason I've come up with is that strict cladists just don't like it and will defend their peculiar definition of monophyly "to the death").




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