[Taxacom] Are slugs subgroup(s) of snails

Barry Roth barry_roth at yahoo.com
Fri Sep 4 17:24:42 CDT 2009

This thread reminds me of an observation I made many years ago, and got a few lectures out of, and just now toss out for whatever use anyone can make of it.
Although the limpet shell form (defined as a bowl-shaped or cap-shaped shell that covers the entire gastropod animal) is widespread and convergent in many groups of marine gastropods, and is present (if not really common) in freshwater gastropods, there seem to be no fully terrestrial limpets.  There are, of course, the semislugs that have been remarked on, in which the coiling geometry produces a bowl- or cap-shaped shell (with the spire barely present), but that shell is usually small with respect to the total size of the animal.  For whatever reason, the limpet form does not seem to "work" in the terrestrial realm.
Barry Roth

--- On Fri, 9/4/09, Kenneth Kinman <kennethkinman at webtv.net> wrote:

Dear All, 
     I forgot about limpets.  So I looked up the German word for limpet,
and it is Napfschnecke (i.e., "bowl" snail, from the shape of the
shell).  Like Nacktschenke, this common name also indicates a belief
that limpets are viewed as a particular kind of snails.  
     This further solidifies my view that there are two different
meanings of "snail" out there, and when someone says snail, you can't
always know for sure whether they are using it in the broad sense
(gastropods in general) or in the narrow sense (gastropods living in a
coiled shell).  Those who use it sensu lato would not agree with
Francisco that Tandonia are NOT snails.  They would regard Tandonia as
Nacktschenken (naked snails), often also referred to by the English word
slugs.  Something to keep in mind.  
I wrote:
      Francisco wrote that Tandonia are slugs, not snails.  I guess this
depends on how one defines a snail.  If it must have a shell to be a
snail, then I guess this is true.   However, the word snail seems to
originate from the German Schnecke, which can mean either snails sensu
stricto (shelled forms only) or sensu lato (snails and slugs), depending
on the user. 
       The specific German word for a slug is Nacktschnecke, literally
meaning "naked snail".  Therefore, this indicates that at least some
Germans must have regarded naked snails (slugs) as a subset of snails.
Maybe this is a good thing, as it would clearly indicate their
relationship, especially to those who might think slugs are some kind of


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