Turrids are often extremely specific in their choice of prey: They are the "specialists" of the
shell world - a species of Turrid may feed on just a few or even one species of Polychaete, for
example.  This partly explains why so many Turridae can inhabitat seemingly very similar habitats:
in small material from a tiny area in the Phillipines, i have found about 180 Turrids under 15mm,
for example!  This prey-specificity also to some extent controls their ranges: a species with a
wider variety of prey, or on prey that have a large geographic range themselves, will usually have a
larger range than one that feeds only on one prey species endemic to a small area.  Many of the
Turrids in my area are Circumboreal or even Panarctic, but others are much more restricted - one
that i found in what appears to be a post-glacial refuge (a small depression off SW Nova Scotia
which contains molluscan fauna far more typical of sub-artic regions), appears to be endemic to that
very small area - but this may be more a function of geographic isolation than restriction due to prey-specificity.
        It is  the radula (a tiny "harpoon", notoriously difficult to extract intact from the animal!!)
that specializes, far more than the shell, so it is highly probable that there are many
"cryptospecies" in this family - species which may be conchologically inseparable, yet have radulae
and behaviors specialized for different prey - this is a taxonomist's nightmare, given that Turridae
are already by far the largest and most confusing molluscan family on the planet, even just looking
at conchological features!!!
Cheers,
Ross M.
--
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