Mollusc outgroups (was 'cladistics' of sequences)

[Ken Kinman]

John Grehan wrote:
     No, but if one cannot polarize the characters and determine which are potential synapomorphies before the analysis then the implication is that such individuals do not know their group very well.
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     Not necessarily.  In the case of Mollusca, I believe that many hundreds (maybe thousands) of malacologists know the details of that group better than I do.  However, I still think that they probably have severely misrooted molluscan phylogenies due to a mistaken notion of what (1) an "Urmollusc" was really like.  The same goes for (2) the "Urarthropod" with multiple identical repeated segments,  (3) various hypotheses of the Urbilateria, and (4) Woese's concept of a hyperthermophilic cenancestor of all life (remember his 3 Urkingdoms?).

     If such mispolarization of characters do occur at thedse highest taxonomic levels by scientists who know their taxa fairly intimately, the same thing can also repeatedly occur at various lower taxonomic levels as well.  The double whammy of homoplasy and misrooting is something of which we should always be wary.  Even Thomas Cavalier-Smith (for whom I have the greatest respect) was mistaken about the nature of the earliest eukaryotes, but he admitted the error and has moved on.  I can only hope there will be similar admissions of error by others and a timely "moving on" to other rootings of the appropriate taxa.  Whether or not great apes have been misrooted still remains to be seen.  Personally, I am still hoping for the relatively neglected phylogeny:  Pongo (Homo (Pan, Gorilla)).
            ------ Cheers,
                      Ken Kinman