Now the discussion is veering into an area that REALLY interests me -- the Cambrian. My understanding of Hallucigenia is that this beast was originally reconstructed upside-down! It was shown walking on stiff legs, which later turned out to be spines on its back. Another infamous mistake involves the Anomalocaris, which was the nastiest predator of its era. When it was first described, researchers only had claws and the circular grinding mouth, the hardest parts of the animal and the parts most likely to be fossilized. They thought the mouth was a jellyfish and the claws were shrimp. Only much later were paleontologists able to put together the pieces and realize what a monster it was. Meanwhile, it remains named for a shrimp. A page on the Internet about the animal is: http://www.trilobites.info/anohome.html One thing I want to mention about the discussion is that the swift, amazing increase in lifeforms happened during the Cambrian, not the Precambrian era. The Precambrian lasted billions of years and there are few fossils remaining from that time. But suddenly during the Cambrian, the types of animals increased so fast that it's called the Cambrian Explosion. I'm glad you mentioned Wonderful Life. While there is severe criticism of Gould's theory of "punctuated equiberium," this is a fantastic book to learn about life in the Cambrian. My favorite book, so far, about the subject is "Fossils of the Burgess Shale," published by the Smithsonian. I got my copy by ordering from them. There's a new book out about some possibly even more astonishing finds in China, but I haven't seen it yet. Best wishes, Joe
--- Dave Gary <Dave.Gary@m.cc.utah.edu> wrote:
Actually, different body plans are represented by the phyla. There are, approximately, 37 phyla, therefore, there are 37 different body plans. This is the definition of phyla. I don't know where you got your information about 5 different body plans. Again, read James W. Valentine's "On the Origin of Phyla". His material will really get you thinking.
correctly pointing out factual errors in -
On Aug 28, 2005, at 7:33 PM, Canopus56 wrote: <snip>
The pre-Cambrian era is unique in evolutionary history in that nine or so novel new body plans evolved in mutli-celluar organisms in a relatively
short period of geologic time. Of the nine original body plans, only five survive today. No new novel body plans have evolved in the subsequent 560 million years.
Thanks Gary, that'll teach me to write on a Sunday afternoon from memory from Stephen Gould's 1989 _It's Wonderful Life_. I believe the correct statement is there are about 35 phyla (or 35-39 depending on who's counting), but in the pre-Cambrian there were about 50 phyla. The paradox is that so many phyla evolved in a short-period of time and then the diversity of phyla decreased.
Since 1989, further investigation of Gould's interpretation of the pre-Cambian has been rejected and some of the fossils he interpreted as unique phyla have been reinterperted within existing phyla, e.g. Hallucigenia.
Gary, thanks for keeping on me on my toes. It's a complicated question and misstatments of fact do not help.
The factual mistake was not central to the issues regarding ID that I was discussing. In reviewing the the remaining assertions, they look okay to me. Let me know if that's not the case.
- Canopus56(Kurt)
P.S. - Thanks for the reference to "On the Origin of Phyla". I've added it to my Amazon wish list and used book search list.
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