[Taxacom] Evolution of molluscs and other invertebrates

Doug Yanega dyanega at ucr.edu
Thu Jul 9 22:24:11 CDT 2009

Ken Kinman wrote:

>        I continue to be extremely disappointed that there
>is still very little discussion (much less support) on the possibility
>that Class Bivalvia could very well be paraphyletic with respect to
>other classes of molluscs. This hypothesis is strongly advocated by
>myself and by Thomas Cavalier-Smith. After several years, I still see
>noone else discussing (much less advocating) this idea, especially among
>malacologists who really should be those most interested in this
>          As in the case of great apes, I believe whole
>genomes will be the major step in determining the actual
>interrelationships of the molluscan Classes (and other groups which
>could be their descendants---arthropods, annelids, various worms?). As
>the costs of genome sequencing continues to plummet, Phylum Mollusca
>will hopefully become a primary target for analysis. Not only because it
>is a diverse and economically important group, but it is probably
>central to an understanding invertebrate evolution, even more so than
>arthropods which tend to attract relatively more attention.

Wasn't it here where someone just posted a link to the recent 
Goloboff et al. genomic analysis indicating that molluscs were not a 
monophyletic unit? The paper explained that scaphopods and bivalves 
came off the tree sequentially, followed by some other miscellaneous 
invertebrate phyla (presumably "worms"), and THEN came the clade that 
comprised the remaining molluscan classes. That implies that the only 
way to keep mollusca s.l. as a phylum is to either include those 
other invertebrate groups in between, or remove and elevate 
scaphopods and bivalves to become separate phyla. It's not that 
bivalves make the remaining molluscs paraphyletic, it's that they're 
apparently not even in the same phylum! I imagine that the prediction 
that molluscs will "become a primary target for analysis" is probably 
true, but going in a very different direction.


Doug Yanega        Dept. of Entomology         Entomology Research Museum
Univ. of California, Riverside, CA 92521-0314        skype: dyanega
phone: (951) 827-4315 (standard disclaimer: opinions are mine, not UCR's)
   "There are some enterprises in which a careful disorderliness
         is the true method" - Herman Melville, Moby Dick, Chap. 82

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