Bivalves; and Feduccia newsrelease

Ken Kinman kinman at HOTMAIL.COM
Fri Aug 16 19:52:29 CDT 2002


    Yes, an interesting exchange of ideas on the Mollusca list, which I plan
to pursue further (especially on the fossil record).  But there are also the
semantic quibbles to sort through so that everyone understands one another.
     I've learned that bivalves are not technically "headless", just
buccal-less (in any case, I still think it's probably primitive rather than
secondary).  And bryozoan cyphonautes larvae might not technically have
"shells"----I guess "valves" is more accurate, but my main point is that
they are probably homologous to bivalve shells.  An entoproct larva with
cyphonautes-type valves would be a great model for a bivalve ancestor.  I
agree with Nielsen that entoprocts and ectoprocts are closely related,
although I totally reject his belief that these two groups form a
holophyletic clade.
     And however the xenoturbellid debate turns out is not really all that
central to my arguments overall.  More importantly, if a typical bivalve can
evolve into something like a shipworm, then bivalves could also evolve into
worms which have lost the shells altogether (especially sipunculids, but
perhaps other spiralian worms as well). Could nemertines or some flatworms
actually be very-derived bivalve "slugs"?   If snails can do it, why not
bivalves?  Who knows!!??  I am particularly interested in the shells of
sternaspid polychaetes (perhaps remnants that offer a clue that polychaetes
might have evolved from bivalves??).
     Should be interesting to see what comes out of all this brainstorming
and exchange of ideas.  Reminds me of something Darwin once wrote, something
like "without imagination, there is no true and good science".  I like that
point of view.
            ---- Cheers,   Ken
P.S.  For those of you interested in birds and dinosaurs, Alan Feduccia is
in the news again.  See his press release at this URL address:

http://www.unc.edu/news/newsserv/research/feduccia081402.htm

*****************************************
>From: Barry Roth <barry_roth at YAHOO.COM>
>Reply-To: Barry Roth <barry_roth at YAHOO.COM>
>To: TAXACOM at USOBI.ORG
>Subject: Re: -ops family names (plus bivalves)
>Date: Fri, 16 Aug 2002 10:25:07 -0700
>
>In case this sounds like an "up against entrenched authority" spin on the
>transactions over on the Mollusca list, as a participant in both lists, I
>see it somewhat differently.  Ken's initial post was met with serious,
>thoughtful responses, including mention of the fact that the idea of
>Bivalvia as a possibly basal group within (or next to) Mollusca has been
>floated before.  The posts pointed out difficulties with the notion (which
>would have to be overcome before it was adopted as a convincing model), and
>the fact that one of Ken's proffered lines of evidence (a thesis concerning
>the "worm" Xenoturbella) has proven problematic on further study.  I'm not
>sure that the participants have yet achieved any sort of reciprocal
>illumination -- that happens rarely in these settings -- but I was glad to
>see some substantial postings on a list that for weeks at a time often
>contains little of general interest (big surprise). :-)
>Barry
>  Ken Kinman wrote:P.S. By the way, discussions about bivalves and
>molluscan evolution are
>taking place on the "molluscalist" newsgroup through UC-Berkeley. So I
>guess I'll get back to that debate, since the "bivalves-first" hypothesis
>is
>meeting with stiff resistance (no big surprise). :-)
>
>
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