A skull cast and head reconstruction of Nigersaurus taqueti, seen at the Sternberg Museum in Hays, Kansas:
Nigersaurus lived in the middle Cretaceous period, 119 to 99 million years ago, in what is now Africa. A sauropod standing 8 feet (2.5 meters) high at the hip, and about 30 feet (9 meters) long, nigersaurus weighed 4 tons. Its straight rows of teeth were tailor-made to clip vegetation off like a lawn mower — making it a fairly large analog of a modern-day cow.
What made this beast unique was that it had more than 50 columns of teeth, with each cutting tooth being backed by up to nine replacements. When a cutting tooth wore out, another immediately took its place — likely happening about once a month in each column. Nigersaurus was first described in 1976, and in fact is quite common in fossil beds in the Niger Republic. But because its bones are delicate and filled with air pockets, it wasn’t well described until an articulated specimen was found and published in 2005.