Chordate of the three subdivisions of chordates, all have distinct skulls. They include the hagfish, which have no vertebrae. Michael J. Benton commented that "craniates are characterized by their heads, just as chordates, or possibly all deuterostomes, are by their tails". Most craniates are vertebrates, in which the notochord is replaced by the vertebral column. These consist of a series of bony or cartilaginous cylindrical vertebrae, generally with neural arches that protect the spinal cord, and with projections that link the vertebrae. However hagfish have incomplete braincases and no vertebrae, and are therefore not regarded as vertebrates, but as members of
Cruelty to animals training of performing animals. Numerous instances of animal abuse in circuses have been documented such as confining enclosures, lack of regular veterinary care, abusive training methods and lack of oversight by regulating bodies. Animal trainers have argued that some criticism is not based on fact, including beliefs that shouting makes the animals believe the trainer is going to hurt them, that caging is cruel and common, and the harm caused by the use of whips, chains or training implements. Some circuses now present animal-free acts. Bolivia has enacted what animal rights activists called the world's first ban on all animals