The zone between Africa and South America had always been a volcanic "suture" area with a series of narrow sea lanes (like Baja California). It was an area called The "Dom Feliciano Belt" So there was an area roughly from todays Brazil to Tierra del Fuego that hd a bout a 50 mi wide strip of ocean separating Africa from it. North of that there was a free exchange of animals (some of the biggest African dinos are actually found in the Sahara.
Then, about 110 million years ago, all of S America began rifting from Africa in earnest, pretty much isolating The American dinos from the rest of the world species. South America was being pushed into North America but after about 80 million years the East-West rifting of the area that would become the Gulf of Mexico started and this began the separation of North America from South America for tens of millions of years. That's why South America in post dinosaur days had a different set of pinnacle predators than did North America.(Giant Killer birds in South v mammal predators in the North).
Rogers and Santosh's Continents and Supercontinents
is still one of the best treatises on rifting and continental drift through geologic time