>>    I have had a person contact me through Man and  Mollusc with the
>>following request for help:     "I  am doing a project, can you tell me
>>if molluscs diversified before the Cambrian explosion or during it, and
>>also if  tubeworms are closely related to molluscs. "   If you have an
>>answer for Katie, please contact her in  person at: [log in to unmask]
>>Thank you,   Avril Bourquin
>>PO Box 366
>>Invermere,  BC
>>Canada
>>V0A 1K0   Email: [log in to unmask]
>>URL: http://www.manandmollusc.net

As far as I know, the position of annelids relative to that of the molluscs
still is a matter of debate. Most scientists place annelids close to
arthropods, but there are some who claim a closer relation (but still not
very close) to molluscs. Within the Annelids, the tubeworms (I presume you
mean Serpulidae with calcareous tubes, there are a lot of non-calcareous
tube-worms around) are fairly derived, thus not very close to the root of
the tree, and certainly not close to molluscs either. You'll find a chapter
on this topic in:

Beesley, P.L., & G.J.B. Ross & C.J. Glasby (eds), 2000.- Polychaetes &
Allies: the southern synthesis. Fauna of Australia. Vol. 4A. Polychaeta,
Myzostomida, Pogonophora, Echiura, Sipuncula. CSIRO Publishing: Melbourne,
xii + 465 pp., 12 pls, 131 + 19 + 18 + 16 pp. [Serpulidae p. 184-189, by G.
Rouse].

Be aware, however, that the so-called Serpula helicalis which is mentioned
in this book as well most probably is not a serpulid, but more related to
molluscs according to:
Weedon, M.J., 1990.- Shell structure and affinity of vermiform
'gastropods'. Lethaia 23: 297-309, 7 figs.
Weedon, M.J., 1991.- Microstructure and affinity of the enigmatic Devonian
tubular fossil Trypanopora. Lethaia 24: 227-234, 5 figs.

dr. Harry A. ten Hove
Zoological Museum,
University of Amsterdam
POB 94766, 1090 GT AMSTERDAM

TEL. 3120 5256906
FAX. 3120 5255402
http://www.bio.uva.nl/zma/
http://www-zma.bio.uva.nl/departments/Coel/coeleng/harry.html