The Mysterious Continuation of Crab Evolution.

The evolution of crabs has resulted in the development and loss of crab-like features at least five times in the past 250 million years, a phenomenon known as carcinization. The reasons for this repeated evolution of the crab-like body plan remain a mystery, but studying crabs provides an opportunity to understand convergent evolution and predict the shapes that evolution might make based on environmental factors and genetic cues. Taxonomists are steadily piecing together what makes a crab, a crab, and resolving the multiple origins and losses of crab body forms through time.