Definition: Given a scientific passage and an answer, generate a question for the given answer.
Input: Passage: Cartilaginous Fish Cartilaginous fish include sharks, rays, and ratfish. Their endoskeleton is made of cartilage instead of bone. They also lack a swim bladder. However, they have a complete vertebral column and jaws. They also have a relatively big brain. shark. Answer: cartilaginous
Output:
Lacking a bony endoskeleton, sharks, rays, and ratfish belong to what group of fish?