What did the haikouella, a primitive early chordate fossil, lack that vertebrates have?

Answer - Skull and Ear Organs

Haikouella, a primitive early chordate fossil which is similar in appearance to to lancelet, was found to have formed-brain, eyes, and muscular segments. However it lacked two major things that vertebrates have, namely skull and ear organs. Additionally, Haikouella had respiratory gills on its pharynx.