Hi ASA
>From: bivalve@email.unc.edu (David Campbell)
>To: asa@calvin.edu
>Subject: Re: Another apologetical mess up
>Date: Mon, 27 Mar 2000 11:11:16 -0500 (EST)
>
> >Reasons to Believe has come up with another factually inaccurate article
> >about the Cambrian explosion.
>
>This particualr topic seems popular to mess up among IDers also. A few
>further corrections:
>
>
>Several other phyla without well-developed skeletons are not known from the
>Cambrian. A few have patchy fossil records; for example, Tardigrada has a
>knwon fossil record confined to a single specimen from Cretaceous amber.
>Also, Bryozoa has a good skeleton but is not yet definitely known from
>before the early Ordovician.
>
>In addition to the body fossil of Kimberella, there are Precambrian traces
>of radular scraping, distinctive of mollusks.
>
I read recently that many of the trace fossils [like feeding trails] can be
explained as due to Cnidarians or flatworms. How late are the mollusc
traces?
> >Annelids are first found in the Precambrian, not the Cambrian: "About 25
> >percent of the specimens collected at Ediacara are annelids. The most
> >common genus, Dickinsonia, may have survived into Paleozoic time. A
>similar
> >form, Spinther, is still living as an ectoparasite on sponges." ~ Preston
> >Cloud and Martin F. Glaessner, "The Ediacarian Period and System: Metazoa
> >Inherit the Earth.", Science, 217, August 27, 1982, p. 788.
>
>Whether Dicknisonia was an annelid remains debated. However, the presence
>of Cnidaria in the Ediacaran seems definite.
There are also assorted
>fossils of uncertain affinities, including conodont-like forms, probably
>either chordates or chaetognaths.
any references for those?
> >Thus the claim that there are all animal phyla are first found in the
> >Cambrian is simply false.
>
>Also, the extremely high estimate for the number of phyla in the Cambrian
>is wrong. The weird forms are increasingly fitting into known groups.
My point entirely. And it has been known for years. I read a Scientific
American article from 1992 that discussed echinoderms and how they'd moved
from a "lawn" of genera to a classical branching tree thanks to better
classification. According to Conway Morris the same has occurred for phyla.
On
>the other hand, there are some later fossils that do not fit, such as the
>Tully monster from the Carboniferous Mazon Creek.
>
Is there a URL for the Monster? What does it look like???
>Another popular error with regard to the Cambrian explosion is to claim
>that there is no evolutionary explanation for it. There are at least half
>a dozen scenarios, mostly not mutually exclusive. Proving that one or
>another was the most important factor may be impossible, but there is
>evidence that some of the potential causes were in place, whether or not
>they had much effect.
>
Another fact that rermains unappreciated is that the rise in numbers of
species is not instantaneous but seems to follow a curve that indicates that
niches were being filled in a pattern that has analogues elsewhere in the
fossil record. There is a clear order to events NOT some sudden "boom".
>To some degree the misuse of this issue seems to serve Gould right for his
>excessive emphasis on randomness in Wonderful Life and the like.
"Contingency" is a better word. The vagaries of history...
However,
>the ability of different people to use the same evidence to support total
>indeterminancy and special design suggests that the evidence is not the
>basis for the decision in either case.
>
>David C.
It certainly doesn't help.
Adam
>
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