Heterotremata

Heterotremata, from Ancient Greek ἕτερος (héteros), meaning "different", and τρῆμα (trêma), meaning "hole", 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
Xantho poressa (Xanthoidea: Xanthidae)
Scientific classification
Kingdom:	Animalia
Phylum:	Arthropoda
Class:	Malacostraca
Order:	Decapoda
Suborder:	Pleocyemata
Infraorder:	Brachyura
Section:	Eubrachyura
Subsection:	Heterotremata Guinot, 1977
Superfamilies
See text

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:^[2][3]

Brachyura	Dromiacea Raninoida Cyclodorippoida Eubrachyura Heterotremata Thoracotremata

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]

Heterotremata

Freshwater crabs Potamoidea (Old World freshwater crabs) Potamonautidae Potamidae Gecarcinucidae Pseudothelphusidae (New World freshwater crabs) Trichodactylidae (freshwater crabs) Orithyiidae Belliidae Chasmocarcinidae Retroplumidae Dorippoidea Ethusidae Dorippidae Leucosiidae Majoidea Inachidae Epialtidae (paraphyletic) Majidae / Mithracidae Corystidae Euryplacidae Matutidae Calappidae Parthenopidae Cancridae Carpiliidae Aethridae Pseudocarcinus of Menippidae Menippe of Menippidae Polybiidae Portunidae Pilumnoidea Tanaochelidae Galenidae Pilumnidae Mathildellidae Eriphiidae Oziidae Vultocinidae Trapeziidae Goneplacidae Scalopidiidae Xanthoidea Xanthidae (paraphyletic) Panopeidae

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:^[2][3]

• 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