There are three subphyla in the chordates-one, the vertebrates, will be covered next chapter. The other two have chordate features but no backbones: The sea squirts or tunicates (technically, urochordates) spend their adult live as sessile creatures, looking like a vase with two openings.here are three subphyla in the chordates-one, the vertebrates, will be covered next chapter. The other two have chordate features but no backbones: The sea squirts or tunicates (technically, urochordates) spend their adult live as sessile creatures, looking like a vase with two openings.