The Trapezioid Crabs

The Trapezioid crabs Tetralia and Trapezia are not actually related. Although they look and behave similarly they are a classic example of convergent evolution. So both families have been placed in the super-family Trapezioidea.
In the old (ie pre-internet) days of diving on Koh Phangan we had little or no understanding of our smaller marine life – now it gets much more understandable!