[Taxacom] Mollusca, major subdivisions

Dr. David Campbell amblema at bama.ua.edu
Tue Mar 17 12:35:27 CDT 2009

> And has ANYONE ever even tried a bivalve outgroup for gastropods???  
If I'm right, that could completely revolutionize the systematics of 
gastropods.  <

Yes, plenty of analyses of gastropods include bivalves among the 
outgroups.  No, it doesn't support the idea that euthyneura is basal in 
Gastropoda; the archaegastropod grade is basal and euthyneurans are 
derived in molecular and morphological analyses alike.  

Worm-like forms are derived secondarily all over the phylogeny of 
Animalia, but it also seems to be the basal bilaterian form.  There is 
still some tendency to assume annelid-like ancestors (if not annelid 
ancestors) for various other phyla when the actual ancestor is likely a 
much more generic, unsegmented worm.

Dr. David Campbell
425 Scientific Collections Building
Department of Biological Sciences
Biodiversity and Systematics
University of Alabama, Box 870345
Tuscaloosa AL 35487-0345  USA

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