Hagfish, lampreys, sharks, and tuna are all chordates that can also be classified into which group?

a. Craniates

b. Vertebrates

c. Cartilaginous fish

d. Cephalocordata

Craniata/vertebrata includes primitive jawless myxini (hagfishes), petromyzontida (lampreys) and all of the organisms called vertebrates. They all possess a cranium. A cranium is a bony, cartilaginous or fibrous structure surrounding the brain, jaw, and facial bones.

Craniata includes the classes, Agnatha, Chondrichtyes, Osteichthyes. Hagfishes and Lampreys belong to the class Agnatha. Sharks belong to Chondrichthyes and tuna belongs to Osteichthyes. Hence, option (a) is the correct answer.

b. Vertebrates

In hagfishes, the notochord is not replaced by the vertebral column so they cannot be considered as true vertebrates. Hence, option (b) is the incorrect answer.

c. Cartilaginous fish

Cartilaginous fish includes only sharks and not hagfishes, lampreys and tunas. Hence, option (c) is the incorrect answer.

d. Cephalochordata

Cephalochordates are invertebrate marine animals. They do not share the same features as hagfish, lampreys, sharks and tunas. Hence, option (d) is the incorrect answer.