Majoidea

Lore & Background

The taxonomy of Majoidea has undergone revision. In 'A classification of living and fossil genera of decapod crustaceans,' De Grave and colleagues originally divided Majoidea into six families. Subsequently, subfamilies Epialtinae and Mithracinae were elevated to families, and Hymenosomatidae was moved to its own superfamily. The World Register of Marine Species now lists eight families: Epialtidae, Inachidae, Inachoididae, Macrocheiridae, Majidae, Mithracidae, Oregoniidae, and the extinct †Priscinachidae. The fossil family †Priscinachidae is represented by a single species, Priscinachus elongatus, from the Cenomanian of France.

Reader's Guide

Majoidea's significance lies in its diversity and the notable species it contains. The superfamily includes the Japanese spider crab (Macrocheira kaempferi), the largest living species of crab, found on the bottom of the Pacific Ocean. Other notable species include Libinia emarginata, the portly spider crab, found in estuarine habitats on the east coast of North America; Hyas, a genus including the great spider crab (Hyas araneus), found in the Atlantic and the North Sea; Maja squinado, sometimes called the 'European spider crab'; and Australian spider crabs, found off Tasmania, which are known to pile up on each other, with faster-moving crabs clambering over smaller, slower ones. The taxonomic revisions reflect ongoing scientific understanding of the group's relationships.

Did You Know?

• Majoidea contains the largest living species of crab, the Japanese spider crab (Macrocheira kaempferi).
• The classification of Majoidea has been revised, with subfamilies Epialtinae and Mithracinae elevated to families and Hymenosomatidae moved to its own superfamily.