Once again, it isn't quite so suddenly. The first fossil chordates, are
invertebrates. These animals had a soft-tissue nerve cords running down
their back, but they had no actual backbone. Carroll says
"None of the early vertebrate groups shows evidence of a bony internal
skeleton." Vertebrate Paleontology and Evolution p. 23
Consider the earliest chordate (which had no vertebrate spine)
The first chordate recorded from the Early Cambrian is the cephalochordate
Yunnanozoon lividum from the 525 million-year-old Chengjiang fauna.
Cordate features of Yunnanozoon are a notochord and an expanded
filter-feeding pharnyx with an endostyle. Segmented musculature and
metameric branchial arches are shared with cephalochordates and craniates.
Metameric gonads and an anteriorly extended notochord indicate
cephalochordate affinities. Yunnanozoon expands the range of
cephalochordate morphology known from the younger Pikaia gracilens and
crown group forms such as amphioxus. Our identification predicts that other
chordate clades (tunicates and craniates) had evolved by the Late
Atdabanian, in the main burst of the Cambrian Explosion" ~ J. Y. Chen, et
al, "A Possible Early Cambrian Chordate," Nature, 377, Oct. 26, 1995
>The issue
>seems to be almost taboo for both sides. I wonder why. Maybe
>it's simply that the matter is so opaque that it's boring.
It isn't taboo. Can you cite some evidence that the cambrian explosion
isn't being discussed? The fossil evidence clearly shows that invertebrate
chordates first appear followed by chordates with vertebrae. So your
assertion that vertebrata evolved suddenly isn't the case, unless you think
10-20 million years is 'suddenly'
glenn
Adam, Apes and Anthropology
Foundation, Fall and Flood
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