Introduction
The Brachyura or "true crabs" are by far the most diverse group of decapod Crustacea with over 7,000 extant species. Typically, they have a flattened, broadened carapace and a greatly reduced abdomen folded underneath the body – features which have also evolved independently in several families of Anomura. Brachyuran crabs have been able to colonise and diversify in an extraordinary range of habitats from deep sea hydrothermal vents below 3,600 m to alpine streams up to 4,000 m. — John W. Short, 2026
Diagnosis
Carapace typically enlarged compared to reduced abdomen; antennular flagella usually short; first pereiopods developed as chelipeds; pereiopods 2–5 usually well developed, pereiopod 5 rarely strongly reduced or vestigial, pereiopods 2–5 typically non-chelate, pereiopods 4–5 sometimes subchelate or chelate; abdomen without tail fan, often flattened and reduced, folded underneath body; first and second male pleopods modified as gonopods; eggs incubated underneath abdomen on pleopods. — John W. Short, 2026
