Re: Stasis in the fossil record.

Karen G. Jensen (
Wed, 19 Nov 1997 17:53:10 -0600

Thu, 13 Nov 1997 11:58:33 -0600 (CST) James Mahaffy wrote:

>There has been some posts about organisms that have not shown a lot of
>change over quite a bit of time. Let me indicate, as someone who
>studies fossils (Carboniferous Coal Swamps), that long periods of stasis
>little change in a taxon is a very real thing in the fossil record and
>not limited to the few examples of Ginkgo or horseshoe crabs.
>Many organisms appear rather abruptly in the fossil record and some last
>long periods without much change. This is especially true if you are
>looking at the more general form (generic or higher taxon level). Of
>course there are always those that emphasize the differences and those
>who emphasize the similarities. One good example of this is the
>Psaronius tree that appears fairly suddenly in the Carboniferous yet
>fits very well and is classified in a with a modern order of tree ferns
>(Marattiales - I just covered these in plant morph).

Yes. Many types of plants found as Mesozoic fossils are extant, at the
family and genus level -- not only this tree fern, but also Lycopods,
Selaginellas, Isoetes, as well as many ferns besides the Marats (pardon the
abbreviations) such as Osmunds, Gleichs, Matons, Dipters, Polypods,
Dicksons, Schizs, Cyaths (more abbreviations), in addition to gymnosperms
including Cycads, Podocarps, Araucarias, Sequoias, etc, and angiospems
including Platanus (Sycamore), Palms, Magnolias, and many others preserved
in Cretaceous deposits.

>But then remember we don't yet see any angiosperm fossils in the
>Carboniferous coal-swamps and somehow that also has to fit into your

The mid-Cretaceous entrance of abundant angiosperms is an interesting
challenge to both the creation/flood and the evolution/long ages scenarios.
Let's share our theories on that one!