Lower Cambrian Deuterostomes from Chengjiang - evidence of vertebrates before the Mid-Lower Cambrian

The Deuterostomes (translating as "mouth second") are a major animal taxon that further divide into the echinoderms (e.g., crinoids, starfish, urchins) and the chordates (e.g., humans, fish and other vertebrates). The deuterostomes belong to a larger group within the Animalia called the Bilateria, owing to bilateral symmetry with a left and a right side to the body plans: note that some deuterostomes are bilateral as embryos, later maturing to have radial symmetry.

Shu, et. al. (Ref) the Chengjiang fossil-Lagerstätte, report a suite of fossils, representing at least four taxa, from the Chengjiang fossil-Lagerstätte that are characterized by a bipartite body, the anterior section of which has a series of perforations, evidently precursors of gill slits; note that jawless fish probably did not occur until the Lower Ordovician. These fossils appear to be primitive deuterostomes. If so, they could present the common ancestor of many animals that appeared and radiated in the Cambrian Explosion, and ultimately all of Phylum Chordata and the vertebrates. These discoveries significantly predate previously published reports, but they also imply that even more primitive vertebrates had evolved before the mid-Lower Cambrian.

Shu, D-G.; Luo, H-L.; Conway Morris, S.; Zhang, X-L.; Hu, S-X.; Chen, L.; Han, J.; Zhu, M.; Li, Y.; Chen, L-Z. (1999): Lower Cambrian Vertebrates from South China. Nature 402: 42-46.