>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:
>While it is true that the majority of the phyla do appear in the Cambrian
>(but not all at once) there is one animal phyla that has no fossil record
>and was only discovered in 1995. The report can be found at: Petar Funch and
>Reinhardt Mobjerg Kristensen, "Cycliophora is a new phylum with affinities
>to Entoprocta and Ectoprocta," Nature, 378, Dec. 14, 1995, p. 711.
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.
>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.
>And last but not least, phylum protozoa has been found in the Precambrian.
Protozoans tend to be recognized as their own kingdom, if not multiple
kingdoms, in current classification.
>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. On
the other hand, there are some later fossils that do not fit, such as the
Tully monster from the Carboniferous Mazon Creek.
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.
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. 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.
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