Microdecemplex rolfei, gen. and sp. nov., a new microarthropleuridean less than 5 mm long, is described from the Middle Devonian Panther Mountain Formation of New York State, U.S.A. The specimens consist of organically preserved cuticle, with some preserving the only cephalic structures known for arthropleurideans. A new order, Microdecemplicida, and a new family, Microdecemplicidae, are established. The probable phylogenetic position of the Microdecemplicida as one of the basal clades of Diplopoda is proposed.
