apatosaurus

Large plant-eating dinosaur, formerly called brontosaurus, which flourished about 145 million years ago. Up to 21 m/69 ft long and 30 tonnes in weight, it stood on four elephantlike legs and had a long tail, long neck, and small head. It probably snipped off low-growing vegetation with peglike front teeth, and swallowed it whole to be ground by pebbles in the stomach.