They're observed moving on a tiny scale, they're not about to float halfway across the Earth, even in millions of years.
Since the distribution of modern wild flora and fauna is a direct result of the distribution of prehistoric flora and fauna, I will continue. The continents have always been roughly as they are now, though sea-levels have fluctuated throughout natural history. The simple fact of the matter regarding fossil and biological evidence is that dinosaurs travelled between the continents using boats, often taking their crops and livestock with them. In this way, species of the same genus colonised much of the world's landmass, just as humanity has done millions of years later.