Which animal phylum is most closely related to the phylum chordata?

I know the wolf belongs in the Phylum Chordata :P

Chordata/e are:

~ animals that have a notochord that supports the body (or a backbone) - it includes all vertebrates.

~ all pilsterally symmetrical

~ have a nerve chord running down the back

These can rage from

- cows

- sheep

- dogs

- cats

- elephants

- giraffes