Lori,
Perhaps one of our more informed can expound on these more thoroughly, but
since you've had no response......

Mollusks are found as far back as the fossil record extends for
macro-creatures...not one-celled critters.  They apparently were pretty
much fully diversified by the time they show up as fossils....So we are
lacking a big chunk of their evolution....

We don't know from which group they arose, but annelids (worms) seem to be
the best fit for their closest relative.....however, many questions persist.

I'm not sure on who or what shows up first in the fossil record, but as I
said above, mollusks seem to have been fully diversified by the time they
do show up.  To give you an idea of how old these animals really
are.....I'll use the Paleozoic land snails of North America (A. Solem and
E. L. Yochelson. 1979. North American Paleozoic Land Snails, with a Summary
of other Paleozoic Nonmarine Snails.  Geological Survey Professional
Papers, no. 1072:1-42, 10 plates)...."Representatives of three orders and
five families of land snails appear essentially simultaneously in the
fossil record of the Pennsylvanian.  These families persist today, thus
demonstrating that in the early late Carboniferous, the land snails had
achieved a high and stable level of diversity (pg. 1)."  I find this
amazing....and when you think that these little babies probably arose from
an already diverse marine fauna....well, it boggles the mind.  All those
vertebrates are cool, but they are short-lived, minor groups when you
compare them to mollusks.

We don't know what, if anything, evolved from mollusks......

Perhaps someone with access to the Treatise on Invertebrate Paleontology
will further enlighten you and yours....

Kurt

At 09:06 PM 1/3/2000 -0500, you wrote:
>Dear Conch-l,
>
>I was wondering... what the current thought is as to when molluscs first
>appeared in history?  What did molluscs descend from?  What order did
>molluscs appear?  What descended from molluscs?
>
>My father asked me the first question recently during a meal we were
>sharing.  I couldn't answer his question and spent a few days pondering
>with no resolution.
>
>Thanks,
>
>Lori Schroeder
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>