Dendrolagus mbaiso n. sp. is a distinctive black and white macropodid which inhabits high elevation mossy forest along the southern and western slopes of the Maokop (Sudirman Range), Irian Jaya. It is of great cultural significance to the Moni people of the western Maokop. Among this language group, Dendrolagus mbaiso n. sp. is protected by specific socio-religious taboos which forbid its hunting and consumption as meat by the members of certain descent groups. Such traditional protection has aided its survival. Cladistic analysis reveals that Dendrolagus mbaiso n. sp. is a member of the ‘derived group’ as defined by Groves (1982) and Flannery and Szalay (1982). Its adaptation to a terrestrial lifestyle has resulted in considerable convergence with more plesiomorphic species of Dendrolagus as well as with other (terrestrial) macropodids.