- A phylum of the Metazoa that includes the classes Crustacea (crabs, shrimps, crayfish, lobsters), Insecta, Arachnida (spiders, scorpions, mites, ticks), Chilopoda (centipedes), Diplopoda (millipedes), Merostomata (horseshoe crabs), and various other extinct or lesser known groups. A. forms the largest assemblage of living organisms, 75% insects, of which over a million species are known. [arthro- + G. pous, foot]
* * *Ar·throp·o·da är-'thräp-əd-ə n pl a phylum of invertebrate animals (as insects, arachnids, and crustaceans) having a segmented body and jointed appendages, usu. a shell of chitin molted at intervals, and an anterior brain dorsal to the alimentary canal and connected with a ventral chain of gangliaar·thro·pod 'är-thrə-.päd adj or nar·throp·o·dan är-'thräp-əd-ən adj
* * *Ar·throp·o·da (ahr-thropґə-də) [arthro- + Gr. pous foot] a phylum of the animal kingdom composed of organisms having a hard, jointed exoskeleton and paired, jointed legs, and including, among other classes, the Arachnida and Insecta. Many species are important medically as parasites or as vectors for disease-causing organisms.
Medical dictionary. 2011.