Simplify the following text for a Grade 9 native English-speaking person.
Original: Its fossils were found in the late Campanian-age Upper Cretaceous Cerro del Pueblo Formation ( about 73.5 million years old ) , near Rincon Colorado , Coahuila , Mexico .
Simplified: Its fossils were found in the Upper Cretaceous Cerro del Pueblo Formation ( about 73.5 million years old ) , near Rincon Colorado , Coahuila , Mexico .