Wegener used plant and animal fossils to support his theory of continental drift primarily through the argument that D. the continents must have been connected at one time and they have moved since then.
He observed that identical fossils of plants and animals, such as the Mesosaurus, were found on continents that are now separated by vast oceans. This suggested that these species could not have crossed the oceans and indicated that the continents were once joined, allowing for the distribution of these organisms.