Heterotremata
# Heterotremata

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.

## Evolution

Heterotremata is the sister group to Thoracotremata within the clade Eubrachyura, having diverged during the Cretaceous 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:

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:

## Superfamilies

* Aethroidea
* Bellioidea
* Bythograeoidea
* Calappoidea
* Cancroidea
* Carpilioidea
* Cheiragonoidea
* Corystoidea
* Dairoidea
* Dorippoidea
* Eriphioidea
* Gecarcinucoidea
* Goneplacoidea
* Hexapodoidea
* Leucosioidea
* Majoidea
* Orithyioidea
* Palicoidea
* Parthenopoidea
* Pilumnoidea
* Portunoidea
* Potamoidea
* Pseudothelphusoidea
* Pseudozioidea
* Retroplumoidea
* Trapezioidea
* Trichodactyloidea
* Xanthoidea

However, recent studies have found the following superfamilies and families to not be monophyletic, but rather paraphyletic or polyphyletic:

* The superfamilies Calappoidea, Eriphioidea, and Goneplacoidea are polyphyletic
* The superfamily Potamoidea is paraphyletic with respect to Gecarcinucoidea, which is resolved by placing Gecarcinucidae within Potamoidea
* The Majoidea families Epialtidae, Mithracidae and Majidae are polyphyletic with respect to each other
* The Xanthoidea family Xanthidae is paraphyletic with respect to Panopeidae
