Kingdom Animalia Infraorder Brachyura Phylum Arthropoda Rank Section | Subphylum Crustacea Scientific name Eubrachyura Higher classification Crab Order Decapoda | |
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Lower classifications Heterotremata, Grapsoidea, Majoidea, Ocypodoidea, Portunidae | ||
Eubrachyura is a group of crustaceans (ranked as a "section") comprising the more advanced crabs. It is divided into two subsections, based on the position of the genital openings in the two sexes. In the Heterotremata, the openings are on the legs in the males, but on the sternum in females, while in the Thoracotremata, the openings are on the sternum in both sexes. This contrasts with the situation in other decapods, in which the genital openings are always on the legs. Heterotremata is the larger of the two groups, containing the species rich superfamilies Xanthoidea and Pilumnoidea and all the freshwater crabs (Gecarcinucoidea, Potamoidea). The fossil record of Eubrachyura extends back to the Cretaceous; the supposed Bathonian (Middle Jurassic) representative of the group, Hebertides jurassica, ultimately turned out to be Cenozoic in age.