Question

Which group are called craniates and why?

Answer 1

Craniates are a group of chordates that includes all vertebrates such as amphibians, birds, reptiles, mammals and fishes 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 (cranium), vertebrates are referred to as craniates.

Complete answer:
Craniata is a subclassification of phylum Chordata. Craniata members have a cranium, which is a bony, cartilaginous, or fibrous in structure which surrounds the brain, jaw, and facial bones.
Vertebrates include complex chordates which have a brain and a brain box. The notochord is wholly or partially replaced by a vertebral column. The development of the vertebral column is always accompanied by the appearance of skeletal structures around the brain and the sense organs to form a cranium. Hence, vertebrates are called craniates.
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.
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.

Note:
Vertebrates are the largest group of chordates, with more than 62,000 living species, which are grouped based on anatomical and physiological traits. 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.