Joined: Oct. 2011
|Quote (oldmanintheskydidntdoit @ Nov. 01 2011,04:21)|
|Quote (forastero @ Nov. 01 2011,02:35)|
|Quote (rossum @ Oct. 25 2011,15:39)|
|Quote (forastero @ Oct. 25 2011,01:10)|
|No wonder yíall wont try †to explain to me †the origin of the up to 100 different Cambrian phyla.|
Some advice. †You really need to check your information before posting here. †We have only identified 13 phyla that were present during the Cambrian, and four of then were also present in the Vendian, before the Cambrian started.
It is possible that a few other phyla were present during the Vendian or Cambrian, it is just that we do not have any fossil record of them -- think small and squishy marine invertebrates that don't fossilize well.
It is worth pointing out that all land plant phyla started after the Cambrian. †Not a lot of ID sites wittering on about the "Cambrian Explosion" tell you about that. †Yet another reason to check your sources carefully.
Described recently as "the most important evolutionary event during the entire history of the Metazoa," the Cambrian explosion established virtually all the major animal body forms -- Bauplane or phyla -- that would exist thereafter, including many that were 'weeded out' and became extinct. Compared with the 30 or so extant phyla, some people estimate that the Cambrian explosion may have generated as many as 100. The evolutionary innovation of the Precambrian/Cambrian boundary had clearly been extremely broad: "unprecedented and unsurpassed," as James Valentine of the University of California, Santa Barbara, recently put it † Lewin, R. (1988) Science, vol. 241, 15 July, p. 291
And they werenít ďallĒ squishy invertebrates either. Heck, even fish have been found in the Cambrian
Shu, D.-G., Conway Morris, S., Zhang, X.-L., Hu, S.-X., Chen, L., Han, J., Zhu, M., Li, Y. and Chen, L.-Z., Lower Cambrian vertebrates from south China, Nature 402:42Ė46, 1999.
Janvier, P., Catching the first fish, Nature 402:21Ė22, 1999.
Shu, D.-G., Conway Morris, S., Han, J., Zhang, Z.-F., Yasui, K., Janvier, P., Chen, L., Zhang, X.-L., Liu, J.-N., Li, Y. and Liu, H.-Q., Head and backbone of the Early Cambrian vertebrate Haikouichthys, Nature 421:526Ė529, 2003.
How long did this "explosion" take again? Remind me.
Wont rightly know fur sure until we reach the promised land but obviously fairly quick since so many are found in the same rock.
Charles Darwin once said " We do not know the ancestors of the Vendian faunas well, and like the Cambrian biota it appeared suddenly in a "complete state" . This is why top evolution gurus Gould and Eldridge came up with their theory of punctuated equilibrium to explain the utter lack of intermediates in the fossil record .
Scientists usually label fossil layers according to geologic eras based on index fossils but they should be labeling them as eco zones. For instance the Cambrian is a seafloor zone that always contains seafloor critters.