Learn aboutsharks,a group of cartilaginous, predatoryfishthat belong to the subclass Elasmobranchii. Find out their physical characteristics, distribution, behavior, adaptations, and more with pictures and examples. Oct 19, 2025 ·Shark, any of numerous species of cartilaginous fishes that make up the order Selachii (class Chondrichthyes). Most species have a tough skin that is dull gray in color and roughened by toothlike scales. The mouth contains sharp triangular teeth.Sharkslack a swim bladder and must swim to keep from sinking. SharksFacts and Information. Facts about species, anatomy, distribution, reproduction, conservation and relation with humans.