calcium: A chemical element and alkali metal that is common in minerals in the Earth’s crust and in sea salt. It is also found in bone mineral and teeth and may play a role in the movement of certain substances in and out of cells.
cartilage: (adj. cartilaginous) A type of strong connective tissue often found in the joints, nose, and ears. In some primitive fish, such as sharks and rays, cartilage provides an internal structure — or skeleton — for their bodies.
extinct: an adjective describing a species for which there are no living members.
say: some outside influence that can change the motion of an object, hold objects closer to each other, or create motion or stress on a stationary object.
Megalodon: an extinct species of shark, Autodus megalodon (Previously Carcharocles megalodon), which lived between the early Miocene (an epoch that began about 23 million years ago) and the late Pliocene (about 2.6 million years ago). Most scientists believe it was the largest fish that ever lived. Its name comes from Greek and means huge tooth. The average adult member of this species is over 10 m (33 ft) and can weigh 30 metric tons (66,000 lb) or more.
the shark: A type of predatory fish that has survived in one form or another for hundreds of millions of years. Cartilage, not bone, gives its body structure. Like skates and rays, sharks belong to a group known as elasmobranchs. They grow and mature slowly and become young adults. Some lay eggs, some give birth to young.
vertebrae: (sing. vertebra) the bones that make up the neck, spine, and tail of vertebrates. The bones of the neck are called cervical vertebrae. Tail bones, for animals that have them, are called caudal vertebrae.
the whale: A general, but fairly vague term for a class of large mammals that live in the sea. This group includes dolphins and porpoises.
