Re: Origin of body plans (phyla)
Arthur V. Chadwick (chadwicka@swau.edu)
Mon, 19 Oct 1998 14:26:35 -0700
At 11:13 AM 10/19/98 -0400, David wrote:
>
>Descendants of transitional forms that retain the transitional features can
>survive after the new form evolves. They generally do not last extremely
>long because the new form is generally better at exploiting the niche that
>it is partly using, but they may either find their own niche or survive a
>while before dying out.
>Further study of late Precambrian faunas will probably extend the ranges of
>both the arthropods (I have heard rumor of trilobites) and the lobopods (by
>identifying the sources of some of the small shelly fossils), so
>conclusions about the relative time of appearance are premature.
David, you are well aware that the trilobites are the first found metazoans
in most places in the world. Where they are not, there are no lobopods
either. Thus you are assuming "descendants" and "transitional", and then
using this assumption to justify your assumption that the evolutionary
history of the trilobites (or "arthropods") involves the lobopods, which
appear after the first arthropods. Does this strike you as a bit
tautological?
Art
http://biology.swau.edu