Why are vertebrates also called craniates?
A) All vertebrates possess skull or cranium
B) All vertebrates possess brain
C) All vertebrates possess coelom
D) All vertebrates possess nerve cord

Hint: A vertebrate is a type of animal that has a spinal cord that is surrounded by cartilage or bone. The term is derived from vertebrae, which are the bones that make up the spine. Birds, fish, amphibians, reptiles, and mammals are examples of vertebrates.

Complete Answer:
Vertebrate, also known as Craniata, any animal belonging to the subphylum Vertebrata, the most common subphylum of the phylum Chordata. They have backbones, which is how they got their name. Vertebrates also have a muscular system composed primarily of bilaterally paired masses and a central nervous system that is partially enclosed within the backbone.
Craniata is a subclassification of Chordata. Craniata members have a cranium, which is a bony, cartilaginous, or fibrous structure that surrounds the brain, jaw, and facial bones. Craniata includes all vertebrates as well as hagfishes (Myxini), which have a cranium but no backbone. Hagfish are the only known living creatures with a skull but no vertebral column.
Because of the presence of a skull or cranium, vertebrates are referred to as craniates. Craniata chordates include the more familiar chordates such as fishes, amphibians, reptiles, birds, and mammals. The vertebrata account for the majority of the extant members of this clade. Because not all of the animals previously known as vertebrates actually had vertebrae, they are now known as the Craniata rather than the Vertebrata.
True vertebrates, which have backbones, are found within Craniates. The notochord is replaced as the primary support for the body by the bony or cartilaginous vertebrae. Vertebrates have a wide range of forms and have evolved to become the most common large animals on the planet.

Therefore, the correct answer is option (A) All vertebrates possess a skull or cranium.

Note:
Craniates have a higher level of activity than tunicates and lancelets. They have a faster metabolism and a much larger muscular system. The muscles that line the digestive tracts of craniates aid digestion by moving food through the tract.