Zoology 10th Edition by Stephen Miller,John Harley

Exercise 4

Similarities between echinoderms and hemichordates warrant their inclusion in the clade Ambulacraria. These similarities include shared molecular characteristics, the presence of a unique tripartite coelom, and numerous developmental characteristics. The Chordata is a monophyletic clade that includes the subphyla Urochordata, Cephalochordata, and Craniata. Contradictory evidence makes the exact relationships among these subphyla uncertain. Members of the infraphylum Vertebrata are the largest and most successful chordates.
What evidence supports the clade Ambulacraria? What evidence supports closer ties of the Hemichordata to the Chordata? What hypothesis regarding hemichordate affinity is better supported by the evidence you list?