Around 385 million years ago, aquatic tetrapods colonized terrestrial environments. We know much about the limb development that this shift from a buoyant to a weight-bearing existence required and shaped, but much less about how these animals managed the equally different sensory challenge of above-water living. MacIver et al. used phylogenetic approaches to document considerable expansions in eye size that occurred well before land colonization. Further, computational explorations of visual acuity show that these expansions, though not particularly helpful for improving underwater vision, would have conferred vast visual improvements in air. The changes likely occurred as a result of a crocodilian-type lifestyle wherein aquatically adapted species floated and foraged on the surface—a lifestyle that both preceded, and prepared species for, subsequent colonization of the terrestrial realm.
Proc. Natl. Acad. Sci. U.S.A. 10.1073/pnas.1615563114 (2017).