What Do All Craniates Have That Earlier Chordates Did Not

Question

What do all craniates have that earlier chordates did not have?
A) brain
B) vertebrae
C) cartilaginous pipe surrounding notochord
D) partial or complete skull
E) bone

Accepted Answer

Craniates have a partial or complete skull, which is a structure that earlier chordates did not have. This is why they are called "craniates" in the first place.

Answer: A, B, D, E
 All of these characteristics distinguish craniates from earlier chordates. They have a brain, vertebrae, a partial or complete skull, and bone (at least some species do). However, choice D is the most specific and accurate answer, as it specifically mentions the defining characteristic of craniates.