ChickenFish

Overheard regarding the Gizzard Shad : “This is the only species of fish that has a gizzard, and so it must be the only fish decended from birds.” This is, of course, untrue. The Gizzard Shad’s gizzard is an adaptation of the normal fish stomach to function like a bird gizzard. This adaptation is an example of convergent evolution, in which multiple instances of a similar functionality evolves separately. Eyeballs with lenses on the edge of clamshells is another example.