I suggest you go to timetree.org. You will find an ebook that gives a very useful introduction to evolution of life, with references. Of course there is a chapter treating the evolution of Chordate. There is also an interesting tool that calculates the date of divergence of any couples of species of the database.
There is a chapter treating the evolution of Chordate. There is also an interesting tool that calculates the date of divergence of any couples of species of the database.