The Uniramia is a mainly abandoned taxon of arthropods, comprising the Hexapoda (insects and allies) and Myriapoda (centipedes, millipedes, and related forms). The uniting feature was the nature of the appendages on the head and the walking legs. The Crustacea were generally considered the closest relatives of the Uniramia, and sometimes were united as the Mandibulata. However, new studies suggest that the Myriapoda are not more closely related to the Hexapoda than the Crustacea, causing the Uniramia taxon to be abandoned. In proposals treating the arthropods as a polyphyletic group, the Onychophora were included here, but this had little support.