Haikouichthys

Haikouichthys /ˌhaɪkuˈɪkθɪs/ is an extinct genus of craniate (animals with notochords and distinct heads) believed to have lived 525 million years ago, during the Cambrian explosion of multicellular life. Haikouichthys had a defined skull and other characteristics that have led paleontologists to label it a true craniate, and even to be popularly characterized as one of the earliest fishes. Cladistic analysis indicates that the animal is probably a basal chordate or a basal craniate;[1]  but it does not possess sufficient features to be included uncontroversially even in either stem group.[2] [3]  It was formally described in 1999.[4]