While on the voyage of the Beagle, Darwin collected the fossils of a Glyptodont, a giant extinct relative of the armadillo.  The armadillo only occurs in South America north to the southern United States.  Darwin wrote, 'On the theory of descent with modification it is at once explained; for the inhabitants of each quarter of the world will obviously tend to leave in that quarter closely allied though modified descendants" or simply the ancestors of species with restricted distributions will be found as fossils in the same area where the descendants occur.   On demonstration are fossil scutes from a Glyptodont found in Florida. These scutes formed the domed cover of the animal.