Lower Cambrian vertebrates from South China

The first fossil chordates are found in deposits from the Cambrian period ( 545-490 million years ago), but their earliest record is exceptionally spor adic and is often controversial, Accordingly, it has been difficult to cons truct a coherent phylogenetic synthesis far the basal chordates, Until now, the available soft-bodied remains have consisted almost entirely of cephal ochordate-like animals from Burgess Shale-type faunas, Definite examples of agnathan fish do not occur until the Lower Ordovician (similar to 475 Myr BP), with a more questionable record extending into the Cambrian, The disco very of two distinct types of agnathan from the Lower Cambrian Chengjiang f ossil-Lagerstatte is, therefore, a very significant extension of their rang e, One form is lamprey-like, whereas the other is closer to the more primit ive hagfish, These finds imply that the first agnathans may have evolved in the earliest Cambrian, with the chordates arising from more primitive deut erostomes in Ediacaran times (latest Neoproterozoic, similar to 555 Myr BP) , if not earlier.