In evolutionary biology, parallel evolution occurs when two independent species evolve together at the same time in the same ecospace and acquire similar characteristics.
Parallel evolution is a different phenomenon than convergent evolution and evolutionary relay. In convergent evolution, independent organisms acquire similar characteristics through their evolution in different habitats (bird and fly wings). Similar to convergent evolution, evolutionary relay describes how independent species acquire similar characteristics through their evolution in similar ecosystems, but not at the same time (dorsal fins of sharks and ichthyosaurs).
A similar banding pattern that is found in almost all species of moths is another example of parallel evolution.