Mandibulata

Mandibulata is a clade within the phylum Arthropoda that unites those arthropods whose mouthparts are formed into mandibles. This contrasts with Chelicerata, which lack mandibles. The group includes three large lineages: Myriapoda (centipedes and millipedes), Crustacea (crabs, lobsters, copepods and related crustaceans), and Hexapoda (insects and their relatives). In many modern classifications, crustaceans and hexapods together form the clade Pancrustacea, with myriapods as a sister grouping within Mandibulata; different schemes reflect ongoing debates about interrelationships among the major arthropod lineages.

Diagnostic features include the jaw-like mandibles at the anterior end and a variety of body plans across aquatic and terrestrial environments. Mandibulates show substantial diversification in body segmentation and appendage specialization, ranging from the many-legged millipedes to the highly reduced or specialized insects.

Phylogeny and fossil record: Molecular analyses consistently support Mandibulata as a monophyletic group. The mandibulate fossil record extends back to the Cambrian, with early representatives among crustacean-like forms. The diversity of mandibulates expanded significantly in the Paleozoic and continues to the present day.