I have collected a fair number of Contraconus species.  The problem of
separating these species is, in part, due to their very limited known
range in time and space.  Normally a species is separated from its parent
by a time gap (so they are not alive together except for a short time) or
a geographic gap (such as both sides of the Panama Isthmus).  But
sometimes they were together for a short time, in the same place, and
there were some intergrades at that time and place.  When you are dealing
with the south Florida fossils, you often are seeing the time and place
of the splitting off of the new species, as well as material mixed in
from earlier and later times (due to dredging operations) and from
disparate environments which may have supported separate species.  Thus
you will often find a few shells that seem to be in between species.  But
if you think it through, that is what you would expect to find under the
circumstances.  Since you are dealing with fossils, you cannot use DNA or
allozyme testing to see if the separate forms are really separate
species.  You cannot tell if you have two slighty overlapping populations
or one population with two common forms (ecophenotypes or the like).
Remember that a fossil collection, even from a small area, will cover a
long time period, much much longer than collections of recent species.
And in southern Florida, the environment changed locally quickly too (as
the sea level went up and down over the centuries/millenia.)  Ed Petuch
is a splitter, but for fossil forms it is more easily justified.  We will
never know which distinct form species were realy just varieties, so you
gain in precision by splitting them(although sometimes you go nuts trying
to decide which species it is--but aren't some modern species like that?)
 Some of Petuch's cone species I cannot agree with (as they seem to
represent extremes within a seemless population), but the Contraconus
species complex seems real, and the names are useful.  If you would like,
call them all subspecies of C. adversarius (Conrad, 1840).  They all are
monophyletic, as was noted.

C. heilprini and C. mitchellorum, both Petuch,1994, are from his Griffin
Pit Fauna of the Okeechobee Formation, which is the topmost (last
deposited, in a few  restricted areas or only preserved in a few areas)
strata in the Caloosahatchee Formation, thus basal Pleistocene
(Calabrian), or roughly 1 1/2 million years old.  There are no
Contraconus species known from younger strata.  They apparently perished
with a lowering of sea level, destroying their protected and restricted
environment.

Allen Aigen :-)  [log in to unmask]