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).
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
-- James F. Mahaffy e-mail: firstname.lastname@example.org Biology Department phone: 712 722-6279 Dordt College FAX 712 722-1198 Sioux Center, Iowa 51250