Earliest fish

In 1999, two fossilized fish species dating back 530 million years were discovered near Kunming, in Yunnan, China. Haikouichthys ercaicunensis and Myllokunmingia fengjiaoa were jawless chordates (animals, including all vertebrates, with a structure known as a “notochord” at some point in their life cycle). Their discovery demonstrated that fish had evolved some 50 million years earlier than had been thought. The two species were entirely new to science, although they are similar to primitive jawless fish such as the Agnathans. Both species have gills, although those of M. fengjiaoa are present in a more primitive arrangement. The announcement appeared in the journal Nature in November 1999.

The fossils were discovered by two separate teams of palaeontologists working in the Chengjiang fauna, a series of fossil-rich sites not far from Kunming in Yunnan, China.

The Agnathan Yunnanozoon lividum, which was active about 525 million years ago during the Early Cambrian period, would have been on one of the evolutionary branches that stemmed from the common ancestor of all vertebrates. The Agnathan line continues today in fish such as lampreys and hagfish.