Decapods
Guides
Crustacea
crustaceans
Crustacea is a major subphylum of arthropods encompassing approximately 67,000 described species, with estimates suggesting this represents only 1-10% of actual diversity. The group includes familiar aquatic forms such as crabs, lobsters, shrimp, krill, and barnacles, as well as terrestrial representatives like woodlice. Crustaceans are united by biramous (two-parted) limbs and characteristic larval development, often involving a nauplius stage. Current phylogenetic understanding places Crustacea as paraphyletic with respect to Hexapoda (insects and allies), with both groups now combined in the clade Pancrustacea. The subphylum exhibits extraordinary morphological diversity, ranging from the 100-micrometer Stygotantulus stocki to the Japanese spider crab with a 3.8-meter leg span.
Pilumnidae
Pilumnidae is a family of crabs in the superfamily Pilumnoidea, characterized by free articulation of all segments of the male abdomen and distinctive gonopod morphology. Members are common in tropical and subtropical intertidal and subtidal habitats, occurring on rocky substrates, coral rubble, and mud. The family has a broad geographic distribution across the Indo-West Pacific, western Atlantic, and other tropical regions, with species often associated with specific habitats such as mangrove mudflats, seagrass meadows, and continental shelf areas.