Mamenchisaurus(马门溪龙) lived about 162 million years ago. It had the longest neck of the animal world. This dinosaur had a neck of about 12metres! It is 3 metres longer than a school bus. But the neck was not heavy. Actually, it was light. About 77% of their neck bones were filled with air.
This dinosaur had a 4-metre-long bone on each side of its neck. The bones supported(支撑) the neck well. This dinosaur could sit on one place while eating tree leaves. The dinosaur did not raise up its head too much. Its neck only moved 20 to 30 degrees. But it was enough for the dinosaur to raise its head 7 to 9 metres high.