some habitat types are environmentally stressful along the parameters
of - for example- salinity and are typically dominated by bivalves, eg
the Neuse River in NC, where it is largely brackish for a decent
length, is dominated by bivalves like Rangia cuneata with nary a
gastropod in sight. Or at least I never saw any from there, first or
second-hand.

In some similar riverine areas on the west coast (eg San Diego River
mouth) a very fast flowing current also seems to create a similar
environment, dominated by species that are infaunal, presumably enough
to avoid bottom scouring, such as Cryptomya californica.

I am sure many other specific examples are out there.

On 1/9/12, Erick Staal <[log in to unmask]> wrote:
> Hi,
>
> When looking at the gastropod genera, the 1:100 ratio looks like just a
> predator:prey ratio, since modern representatives of the genera you're
> mentioning are (at least partially) molluscivorous.
>
> I personally cannot not see how any further information can be inferred
> about the environment from only this ratio (most probably my fault).
>
> Perhaps the bivalve genera present would give more info about the
> substrate (this all under the assumption that genera as an environmental
> indicator stay representative in time, e.g. a silt-dwelling genus in the
> Miocene is still a silt-dwelling genus today, etc.)?
>
> Sincerely, Erick
>
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