How old is the cephalochordate fossil record?

The cephalochordate fossil record dates back approximately 525 million years to the early Cambrian Period.1

While some researchers identify potential chordate-like specimens such as Yunnanozoon lividum and Haikouella dating to 530 million years ago, their classification remains a subject of scientific debate. The primitive cephalochordate Pikaia gracilens, which is often cited as the oldest known fossil chordate, is dated to approximately 505 million years ago.2