[Taxacom] Evolution of molluscs and other invertebrates

Richard Petit r.e.petit at worldnet.att.net
Fri Jul 10 10:21:40 CDT 2009

Outgroups are like rocks.  If you don't think you guessed right the first 
time, you just replace them with rocks you think you can guess better!

Don't forget that Mollusca has bivalved gastropods.

dick p.

----- Original Message ----- 
From: "Kenneth Kinman" <kennethkinman at webtv.net>
To: <taxacom at mailman.nhm.ku.edu>
Sent: Friday, July 10, 2009 10:57 AM
Subject: [Taxacom] Evolution of molluscs and other invertebrates

> Hi Doug,
>       I don't recall a recent paper by Goloboff et al. being discussed
> here (or anywhere else for that matter).  It sounds very interesting!!!
>      There was a paper by Giribet et al, 2006 (in Proc. Natl. Acad.
> Sci., if I recall correctly).  It came up with a new molluscan clade
> called Serialia, but also came up with some strange results (such as a
> polyphyletic Gastropoda).  I strongly suspect that Giribet's choice of
> outgroups was flawed, because if some of those outgroups actually
> evolved from molluscs, then they are actually ingroup taxa (and as I
> have stated before, using ingroup taxa as outgroups totally screws up
> your results, especially for molecular data).
>      In any case, I am not presently advocating removing Bivalvia from
> Phylum Mollusca (I still think gastropods probably evolved directly from
> bivalves).  I will have to see what data (and outgroups) Goloboff et al.
> used.  They had the scaphopods splitting off first???  That sounds very
> odd.  I hope they didn't use annelids (or other worms) in their
> outgroup.  Anyway, I'll have to try to track down their paper.
>            ------Cheers,
>                            Ken
> --------------------------------------------------------
> Doug wrote:
>     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.
> Peace,
> -- 
> Doug Yanega  Dept. of Entomology  Entomology Research Museum
> Univ. of California, Riverside, CA 92521-0314
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