Figure 23.35: The Key Features of Chordates Are Most Apparent in Early Developmental Stages The pharyngeal slits of both the tunicate and the lancelet develop into a pharyngeal basket. (A) The sea squirt larva (but not the adult) has all three chordate features: a dorsal hollow nerve cord, postanal tail, and notochord. (B) All three chordate synapomorphies are retained in the adult lancelet.