Brachyura
Brachyura is an infraorder of decapod crustaceans comprising true crabs. Its members have a short abdomen folded beneath the thorax.
Decapoda: An order of crustaceans characterized by five pairs of walking legs, including crabs, lobsters, and shrimp. Brachyura is one of the major infraorders within this broader crustacean order.
Crab abdomen: The reduced abdominal region of a crab, folded against the underside of its thorax. Its compact form is Brachyura’s defining anatomical feature.
Anomura: A decapod infraorder that includes hermit crabs, king crabs, and squat lobsters. Many anomurans resemble crabs but differ in abdomen structure and evolutionary history.
Blue crab: A swimming crab native to the western Atlantic and Gulf of Mexico, known scientifically as Callinectes sapidus. It illustrates a commercially valuable brachyuran with paddle-shaped rear legs.
Crab evolution: The evolutionary history of true crabs and the diversification of their body forms and lineages. Brachyura’s defining body plan emerged through a long history of diversification.
Malacostraca: The largest class of crustaceans, including crabs, lobsters, shrimp, and krill. This class contains Decapoda and provides Brachyura’s wider taxonomic setting.
Crab carapace: The broad dorsal shell covering a crab’s cephalothorax. Its shape and structure protect the body while allowing the abdomen to remain tucked underneath.
Hermit crab: Anomuran crustacean with a soft, asymmetrical abdomen commonly protected inside an empty shell. Its exposed, often coiled abdomen contrasts with the compact folded abdomen of true crabs.
Dungeness crab: A large edible crab of the northeastern Pacific, Metacarcinus magister. Its fishery shows the economic importance of a temperate brachyuran species.
Decapod phylogeny: The evolutionary relationships among decapod crustaceans, inferred from anatomical and genetic evidence. Phylogenetic research tests how Brachyura relates to other decapod groups.