This is also as good an answer  as any about the other circulating thread about
sub-species (as if we didn't have enough boxes already to sort things into!)

"Andrew K. Rindsberg" wrote:

> Nora,
>
> I thought your question was quite a good one, but meant to say that nature
> doesn't always cooperate with our own, very human categories and ideas. In
> particular, language does not always match reality very well, so we can ask
> a precise, crisply worded question and be appalled by the vagueness of the
> answer, yet learn something from the discussion. A favorite example of this
> kind of problem is to point out that we have words for "blue" and "green",
> but no two people agree on exactly where blue stops and green begins. This
> doesn't mean that blue and green are meaningless concepts, however; most of
> the time we have no difficulty in distinguishing them. Another perennial
> question of this nature includes, "What is a species?"
>
> Yes, the word "species" is applied differently for fossils than for modern
> organisms, because the fossils are incomplete and generally lack soft
> parts, DNA, pigment, etc. (Think of all those cones and cowries that are
> distinguished largely on the basis of color!) The word "species" is still
> meaningful for fossils, because it is applied consistently; species of
> fossil mollusks are based on the shape, internal structure, and composition
> of the shell. We only get into trouble when we slip and try to use modern
> and fossil species in the same database interchangeably, without making
> allowances for the differences. And actually, the differences between
> fossil species and modern species are not as great for the Mollusca as they
> are for some other groups of animals, so we're not in as bad a shape as all
> that. We paleontologists endeavor to persevere.
>
> Andrew K. Rindsberg
> Geological Survey of Alabama