Nigersaurus was discovered in Niger, West Africa. Why would Dr. Sereno and his team explore Africa when there are dinosaurs in North America?

In September of 1997, an expedition led by University of Chicago paleontologist Paul Sereno set out for Niger in search of African dinosaurs --  and clues to the mystery of how the break up of the continents affected dinosaur evolution. To answer this question, you need to do a little traveling on your own- time travel actually. Go back 200 million years to the first half of the Mesozoic Era, when there was a single large landmass. The land was welded together as a single super-continent called Pangaea. About 200 million years ago, Pangaea began to rift apart, with continent-sized slabs of the earth's crust inching away from one another and oceans growing in between.

Pangaea

Africa began to pull apart from South America about 130 million year ago, during the Cretaceous Period. By 100 millon years ago, Africa was surrounded on all sides by oceans and seas. During the later half of the dinosaur era (130 to 65 million years ago), Africa was becoming an island continent.

As the continents drifted apart, dinosaur traffic was greatly restricted. Isolated populations of dinosaurs began to diverge and follow independent evolutionary pathways on each continent. The dinosaurs that roamed the African continent evolved into distinct species, most of which lay undiscovered and unnamed.