Mamenchisaurus lived about 156 to 145 million years ago. It was a long-necked, long-tailed, plant-eating dinosaur. It had the longest neck of any animal that we know of. Mamenchisaurus was about 70 to 80 feet long and weighed about 12 tons. This was about the size of an airplane. Its neck was about 46 feet long, around half of the entire length of its body. It had 19 vertebrae, or backbones, in its neck. This is more than any other dinosaur had. Its neck vertebrae were hollow – and in some places as thin as an eggshell. This made its neck very light, so Mamenchisaurus could move its long neck around easily. Mamenchisaurus held its neck straight out from its body, parallel to the ground. This made it possible for it to eat plants growing low to the ground as well as leaves on high trees.
Mamenchisaurus was an herbivore, meaning that it only ate plants. It lived on conifers, horsetails, club mosses and ferns. These plants had soft leaves, which were easier to digest. It also ate leaves from gingko trees. It moved about slowly on four legs. Its hind legs were longer than the front legs. Not many Mamenchisaurus skulls have been found. From the pieces that exist, paleontologists believe it had a light, box-shaped head like many of the other sauropods during this time. It had blunt front teeth, which it used to tear the leaves off plants. It swallowed leaves whole without chewing them. Along with the leaves, this dinosaur also swallowed small stones. These stones were called gastroliths. They would remain in a dinosaur’s gizzard to break the tough plant food into mush. Once it was a soft paste, the food was passed on to the stomach.
Mamenchisaurus may have traveled in herds or groups. Once the dinosaurs ate everything in their area, they all moved together to a new place. When dinosaurs do this, it is called migrating. Like all other dinosaurs, Mamenchisaurus hatched from eggs. These eggs were not laid in nests, and the babies were not protected by their parents after they hatched. A Mamenchisaurus would lay eggs while she walked and then leave her babies to take care of themselves. These dinosaurs might have lived to be 100 years old. Mamenchisaurus fossils have mainly been found in China. The name means “Mamen Brook lizard”, which tells us where it was found. It lived in wet areas, probably at the banks of rivers and brooks.