Alfred Wagner was a meteorologist who, in 1915, made the case for a theory he called "continental drift." This is the idea that the continents gradually move across Earth's surface as time goes by. Turns out Wagner was right. We now know that, due to plate tectonics, the continents are indeed moving along at a steady pace. And there's more: A century's worth of research has allowed geologists to piece together the travel histories of major landmasses. For instance, scientists have figured out that, after having been separated for tens of millions of years, South and North America were reconnected by the Central American land bridge around 3.5 million years ago.
Still, our knowledge does contain some gaps. Consider Africa. Roughly 300 million years ago, it was part of the supercontinent Pangea. This mega-landmass started to break apart 100 million years later. But we don't know exactly what Africa was doing during certain stages of this process.
The Cretaceous Period lasted from 145 to 66 million years ago. Famously, it ended with a mass extinction that wiped out all dinosaurs, excluding birds. We've uncovered numerous African dino fossils from the early Cretaceous Period — including bones that represent the weird, fin-backed carnivore Spinosaurus. However, late Cretaceous material from Africa is awfully scarce.
One co-author of the Nature study is Ohio University paleontologist Patrick O'Connor. "[T]he late Cretaceous fossil record is quite robust in some parts of the world — like South America, Madagascar and North America," he says in an email. "But by comparison, the late Cretaceous fossil record, and particularly [that] of the end of the late Cretaceous (80-66 million years ago), from continental Africa is a virtual blank slate."
That's a problem for people who study continental drift. Fossil evidence is critical when it comes to theorizing about when, where and how the continents merged or separated. If you find similar-looking fossil remains from the same geologic time on two separate continents, there's a good chance that those landmasses were linked together at some point.
Historically, we haven't been able to compare Africa's late Cretaceous fossil record with that of other continents. As O'Connor pointed out, there simply aren't many African fossils that date back to this time. The information gap has sparked some debate. Without late Cretaceous fossils to work with, paleontologists could only speculate about whether Africa was still connected to South America or Eurasia back then.