The parasitic lampreys, living members of the ____ lineage, have shards of cartilage that partially cover the nerve

cord, which may represent an early stage of the evolution of vertebrae.



a. Petromyzontoidea
b. Placodermi
c. Cephalochordata


d. Urochordata
e. Myxinoidea


ANSWER: a

Biology & Microbiology

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