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From that "NASA article."

The two phyla with durable skeletons that do not appear in Lower Cambrian time, the Chordata and Bryozoa, may have been represented then by soft-bodied lineages, for they have body plans that do not require durable skeletons. Indeed, the chordates appear in the Middle Cambrian, while durable chordate skeletons are not known until the Late Cambrian (Repetski, 1978).

I really, really, really don't like old dates on assertions that there are no fossils for this or that. It's almost self-discrediting on the face of it, even before I bother to go check.

I don't really need to go back and look in this case, either. We've had FR threads on findings of "deep roots and tiny prototypes" for Cambrian body plans.

I'm feeling lazy, so I'll wait for the challenge before I go get it.

For some reason, the quote that I snipped is not a great example of what hit me wrong. For all that, the author's thesis is indeed "shallow roots and no prototypes."

The paper I would guess was written NLT 1980. It's a quarter century old and just wrong.

We know what was going on 700-600 million years ago. There was a big adaptive radiation at the end of the Snowball Earth glaciation.

But we also know "deep roots and tiny prototypes."