The Order Chimaeriformes, commonly known as chimaeras, ghost sharks, or ratfish, is a group of cartilaginous fish related to sharks and rays. They have elongated bodies, large heads with tapering snouts, and long, whip-like tails. Chimaeras are mostly deep-sea dwellers, with adaptations such as large eyes for low-light environments. They possess plakodont teeth for crushing hard-shelled prey like mollusks and crustaceans, and many species have a venomous spine in front of the dorsal fin for defense. Though less familiar than true sharks, chimaeras are an ancient lineage, offering insights into the evolution of cartilaginous fishes.