Before I get classified as a 'justifier' (finding a reason for
any little thing), I'll relate my experience with the Groove-
Toothed Cowry (Cypraea sulcidentata) and other shells.
 
Why does this lovely, endemic Hawaiian cowry have such deeply
grooved 'teeth' around its aperture? I have heard several ideas
over the years but none have the ability to convince. Its deep
teeth give it no noticeable advantage, or disadvantage, over
any other species it might be competing with. Its teeth are
a 'non-factor' in its survival and propagation... but people
agonize over them anyway.
 
Why does a Checker-board Cowry have such a 'HERE I AM!' pattern?
One has to be reminded of the Gary Larson cartoon with one deer
sympathizing to another -- having a bull's-eye on its stomach --
"Bummer of a birthmark, Hal!" Fact is, Cypraea tessellata only
comes out of its deep hidey-hole on the darkest of nights, so
its appearance is a 'non-factor' (or was until humans began
desiring its shell).
 
The point being -- the cutesy spines on some gastropods don't
serve any active role in its life (or death). So before asking
what the function of a feature is, first ask if that feature
has to have a function.
 
Aloha,
 
makuabob (a.k.a. Bob Dayle)