Heterotremata is a clade of crabs, comprising those crabs in which the genital openings are on the sternum in females, but on the legs in males. It comprises 68 families in 28 superfamilies.[1]
Heterotremata is the sister group to Thoracotremata within the clade Eubrachyura, having diverged during the Cretacious period. Eubrachyura itself is a subset of the larger clade Brachyura, which consists of all "true crabs". A summary of the high-level internal relationships within Brachyura can be shown in the cladogram below:[2][3]
The internal relationships within Heterotremata are less certain, with many of the superfamilies found to be invalid. The proposed cladogram below is from analysis by Tsang et al, 2014:[2]
However, recent studies have found the following superfamilies and families to not be monophyletic, but rather paraphyletic or polyphyletic:[2][3]