Imagine huge, long-necked sauropods roaming primeval forests. The dinosaur represented above, Argentinosaurus, lived around 95 million years ago in what is today Patagonia. These giants are thought to be the largest dinosaurs ever to walk the earth, weighing up to 75 tons and growing to 130 feet long; the narrowest part of a leg might be about four feet around.
These were plant-eating dinosaurs whose long necks, light heads and long legs gave them access to the tons of plant material they needed to survive. Paleontologists think they didn’t chew but swallowed plant material whole, which was then digested by bacteria in their stomachs, just like cows. These grazers were social animals and probably moved in herds through the forests. And they nested together: scientists have discovered communal nesting sites where these sauropods laid their eggs. The young were born weighing about 11 pounds: clearly they had to grow very quickly to reach their colossal adult size.