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pterosaurian monophyly



I forwarded to Kevin Padian one of David Peters' (DPTEROSAUR@AOL.COM)
recent messages about pterosaur systematics.  Kevin had already heard
about it from someone else on the list (I'm guessing Jennifer
Allen)...  In any case, Kevin had a few comments that he said I could
share:

  Pterodactyloids may or may not be monophyletic (I think they are,
  based on current analyses), but there is a methodological question
  here that ought to be of central importance to readers of this list.
  One of the tenets of phylogenetic systematics is that you can't
  assert convergence, you have to demonstrate it by showing that
  another phylogeny is better supported.  And that means a full
  cladistic analysis with all the characters.  This argument also
  applies to David Peters's statements (from some weeks ago) that the
  hindlimb characters of pterosaurs and dinosaurs that are interpreted
  as correlated with bipedalism (by me, at least, but what do I know?)
  are probably convergent.  First, you have to show that pterosaurs
  belong to another group -- again, by a full cladistic analysis,
  demonstrating that those of Gauthier, Sereno, and me are not as well
  supported as another explicit hypothesis.  This would require a lot
  of other characters, not just statements that the characters we used
  are probably convergent and therefore can be disregarded.  The
  phylogenies that are currently accepted may well be problematic or
  completely wrong, especially if I had anything to do with them.
  However, the question is one of method, and we don't want to confuse
  ideas of how the evolutionary process worked with ideas of how that
  pattern is structured; instead, we want to test them against each
  other.  For details on this, people can read any recent issues of
  Systematic Biology or Cladistics, or peruse some of the textbooks on
  phylogenetic systematics such as those of Wiley, Brooks & McClennan,
  Cracraft and Eldredge, and so on.

  -- kp

-- 
Mickey Rowe     (rowe@lepomis.psych.upenn.edu)