Evidence supporting continental drifting
The primary evidence for this grouping and the subsequent splitting and drifting is geological. It comes from studies of the way in which today's continents fit together, the continuities of the rocks between their opposite edges, the orientation of magneticcrystals in rocks which shows the position that they held when they were first formed, the dating of the mid ocean ridges and their islands and drillings taken from the ocean floors.
The distribution of many animals and plants adds corroborative evidence. Giant flightless birds provide a particularly clear case since they appeared very early in the history of the birds. One group which included the ferocious Diatryma, evolved in the northern super-continent are all extinct. The other group called ratites evolved in the southern supercontinent, and are represented by the Rhea (Rhea americana) in South America, the Ostrich (Struthio camelus) in Africa, the Emu (Dromaius novaehollandiae) and Cassowary (Casuarius spp.) in Australia and the Kiwi (Apteryx) in New Zealand. These birds are so similar that it seems very probable that they are descended from a single flightless ancestor which had distribution right across the Gondwanasupercontinent. When the land masses separated the different groups of flightless birds continued to evolve independently of each other into their present-day forms.
Other evidence for the splitting up of the super-continents comes from fleas, which are parasitic and travel with the animals they live on but readily develop into new species and move on to new hosts. Some families of highly characteristic fleas are found only in Australia and South America, with the most probable explanation being that they originated on group of animals that had a wide distribution across Gondwana. Botanical evidence is found with the southern beech, a forest forming tree that flourishes only in the temperate lands of the southern hemisphere. This distribution can also be explained by the break-up of Gondwana. During this break-up Africa separated and drifted northwards and Australia and Antarctica remained joined to one another and were linked either by way of a land bridge or a chain of islands, to the southern tip of South America. At this point, it seems, the pouched animals (marsupials) were developing from the early mammal stock. If these developments took place in South America, as some evidence suggests, then the early marsupials could have spread across into the AustralianAntarctic block by way of these land-bridges or by island hopping. Fossil evidence supporting this theory comes from two very closely related marsupial animals; Polydolops and Antarctodolops being found in South America and Antarctica respectively.