The deuterostome ancestor was likely a vermiform worm with gill slits and a central nervous system.

What is it about?

We describe the developmental origins of the chordate morphological characters and show that the same characters develop in hemichordate embryos with the same developmental programs.

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Why is it important?

Until we published our first paper describing the likely deuterostome ancestor in a 2000 PNAS paper, scientists believed that the chordate ancestor would have looked like a tunicate. It is hard to get to a vertebrate from a tunicate, but easier seen and done from a worm-like hemichordate.