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Re: The most important fossil discovery in 2004 (your opinions?)

The structure in the tail is probably a noto-
or stomochord or some other stiffening structure. That such a structure is
ancestral for deuterostomes is indicated by its presence in hemichordates,
the living sister group to echinoderms.

But then larval tunicates have a gut rudiment in their "tail", and the functional anus (in a dorsal position on the trunk) is thought to be tertiary.

If the tail structure is a gut, I
fail to see what the posterior cone could be.