http://en.wikipedia.org/wiki/Chordate
Fossils of one major deuterostome group, the echinoderms (whose modern members include starfish, sea urchins and crinoids), are quite common from the start of the Cambrian, 542 million years ago.The Mid Cambrian fossil Rhabdotubus johanssoni has been interpreted as a pterobranch hemichordate.Opinions differ about whether the Chengjiang fauna fossil Yunnanozoon, from the earlier Cambrian, was a hemichordate or chordate.
Fossils of one major deuterostome group, the echinoderms (whose modern members include starfish, sea urchins and crinoids), are quite common from the start of the Cambrian, 542 million years ago.The Mid Cambrian fossil Rhabdotubus johanssoni has been interpreted as a pterobranch hemichordate.Opinions differ about whether the Chengjiang fauna fossil Yunnanozoon, from the earlier Cambrian, was a hemichordate or chordate.
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