[Taxacom] Outdated classification (was: confused phylogeny)

[Kenneth Kinman]

Dear All,
       Tonight I decided to check out how NCBI was classifying
Acoelomorpha, and given my own reservations and mild conservatism, I was
happy to see that they still place it within Platyhelminthes (as many
morphologists still do).            
       However, I was then horrified to discover that this small bit of
justified conservatism on their part was part of a broader, unjustified
and outdated conservatism in their subdivision of Bilateria into
Acoelomata, Pseudocoelomata and Coelomata.  The Pseudocoelomata in
particular is polyphyletic and has been out-of-date for many years.
There seems to be no mention of Ecdysozoa at all. 
       So my somewhat conservative recommendation (but actually a bit
radical compared to NCBI's badly outdated classification) would be to
divide Protostomia into Cavalier-Smith's Lophozoa, Ecdysozoa and
Platyzoa (and Chaetognatha could be either incertae sedis within
Protostomia or its Ecdysozoa subgroup).  However, NCBI's continuing to
recognize Pseudocoelomata is NOT something that either molecularists or
morphologists would currently favor.       
       In other words, there is a very credible middle ground approach
that NCBI could take here.  Leave Acoelomorpha and Platyhelminthes in
the Acoelomata is fine and probably conservatively prudent.  But their
polyphyletic Pseudocoelomata must be merged with their Coelomata, and
that grouping should instead be subdivided into subgroups such as
Ecdysozoa and Platyzoa.  Cavalier-Smith's other main subgroup Lophozoa
is clearly paraphyletic, but it certainly FAR better than a polyphyletic
Pseudocoelomata (which almost noone has recognized for many years now).     
       Anyway, I see no reason NCBI needs to convert to a radical
division of Bilateria into Acoelomorpha and "Nephrozoa".  However, they
also don't need to be so conservative they they cling to something as
outdated as Pseudocoelomata.  The middle ground is probably most likely
to turn out to be correct, and in any case, it provides a smoother
transition even if a more radical change is eventually needed.  The
molecular cladists are most likely advocating something too radical when
they claim Acoelomorpha is basal to all other Bilateria ("Nephrozoa"),
so it is probably best to resist that radical pendulum swing until they
have more genes (and definitely more lophophorates in their taxon
sampling).      
           -------Ken Kinman