Dear Ross,

It is a matter of tradition.   Turrids are specialized hunters, thus
radulae are quite diverse. Buccinids are mostly scavengers, so their
radulae tend to look about the same.  Once a character's usefulness is
demonstrated in sorting out species, there is tendency to build a taxonomic
scheme based on that character.  Thus, many families are currently
classified on the basis of such monothetic arrangements.  Getting a large,
sensible data matrix takes a lot more time than looking at that one
character.  So, take radulae only for most marine prosobranchs, or just
oviduct loops for hydrobiids, or penial shape for land snails... the risk,
of course, is that there is no way to test for convergence, parallelism or
reversal -all phenomena that are frequent, especially in characters
subjecto intense selection, but can only be detected when looking at many
traits.

Best wishes,

Cristian

(from now on warm Mallorca)

-----Mensaje original-----
De:     J. Ross Mayhew [SMTP:[log in to unmask]]
Enviado el:     miércoles 20 de abril de2005 06:39
Para:   [log in to unmask]
Asunto: Why are radulae sometimes so useful, yet other times almost useless
for taxonomic assignent?

This may seem like a rather naive question, and i already have a few
inkings  regarding possible answers, but i would like to pass it on to
the list, since there are many who are much more well versed in such
maters, and i enjoy learning from them!!!

"Why is it that mollusc radulae are incredibly useful for taxonomic
differentiation in some families such as Turridae, while in other
families such as Buccinidae, often so variable as to be semi-useless for
taxonomic purposes?"

A lot of my postings recieve few responses for some reason, but i hope
those "in the know" regarding this issue, will at least briefly reply to
the list: it is an interesting topic, i think.

 From Sunny, Warm (at least until tomorrow, so i hear...) New Scotland,
Ross Mayhew.

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