Re: soft fossils
James Mahaffy (mahaffy@dordt.edu)
Tue, 10 Sep 1996 09:04:16 -0500 (CDT)> Keith Miller wrote:
>
> This brings up the preservation question in the discussion of the pattern
> of evolution of new taxa. Many living phyla are represented by soft bodied
> forms (nearly half are "worms") that have very poor preservation potential
> and very poor or non-existent fossil records. Thus, when writers declare
> that the fossil record shows that all living phyla appeared at the
> beginning of the Cambrian they are making an _interpretation_ of the fossil
> record. They are assuming the presence of phyla that have no fossil record
> in the Cambrian.
>
> -------
>
To add to what Paul A. said. While the record of hard parts of
creatures is much better - there is some preservation of soft bodied
creatures. In fact there are some exceptional depositional environments
like the Burgess shale that have a lot more soft bodied than hard bodied
creatures and this is a middle Cambrian fauna. It is still true that we
know a lot less about softbodied creatures and there are many for which the
record is VERY spotty - but there is more preservation than one might
think. Another example is the nodules of Mazon Creek, which preserved
some beautiful softbodied creatures of Pennsylvanian age. In fact I
would guess that the fuana from these Lagerstatten (exceptional flora)
are better studied than most other individual sites. It is certainly
ture of both the Mazon Creek and Burgess Shale. Let me still emphasize
that since these are unusual we still know a LOT less about softbodied
creatures so Keith is right. We just know a little bit more than is
implied by his post.
-- :James F. Mahaffy e-mail: mahaffy@dordt.eduBiology Department phone: 712 722-6279Dordt College FAX 712 722-1198Sioux Center, Iowa 51250