Thoracotremata

 ( Crabs ) 

Thoracotremata is a clade of , comprising those crabs in which the genital openings in both sexes are on the sternum, rather than on the arthropod leg. It comprises 17 families in four superfamilies .

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Evolution Thoracotremata is the sister group to Heterotremata 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 Thoracotremata are less certain, with many of the superfamilies found to be invalid. The proposed cladogram below is from analysis by Tsang et al, 2014:

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Superfamilies and families

• Ocypodoidea
• Camptandriidae
• Dotillidae
• Heloeciidae
• Macrophthalmidae
• Mictyridae
• Ocypodidae
• Ucididae
• Xenophthalmidae
• Pinnotheridae
• Pinnotheridae

• Cryptochiridae
• Cryptochiridae
• Grapsoidea
• Gecarcinidae
• Glyptograpsidae
• Grapsidae
• Plagusiidae
• Sesarmidae
• Varunidae
• Xenograpsidae

However, recent studies have found the superfamilies Grapsoidea and Ocypodoidea to be polyphyletic and invalid.

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