Studies on limb bone loading in turtles found that torsion is high relative to bending loads on land, but reduced compared to bending during aquatic rowing. Such changes in shape may have been facilitated by changes in limb bone loading in novel aquatic environments.
In many cases, such transitions are associated with the evolution of flattened limbs that are used to swim via dorsoventral flapping.
Several terrestrial vertebrate clades include lineages that have evolved nearly exclusive use of aquatic habitats.
