Losing legs to facilitate sex: Triramidesmus gen. nov., a new remarkable monospecific genus of the millipede family Polydesmidae (Diplopoda, Polydesmida) from the Altai Mountains of northeastern Kazakhstan

A new genus and species of Polydesmidae is described from the Altai Mountains of northeastern Kazakhstan: Triramidesmus kazakhstanus gen. et sp. nov . The new genus shows a unique combination of characters which are novel in the entire order Polydesmida: incised or lobulated paraterga, 3-branched gonopod telopodites, the presence of a clear-cut accessory seminal chamber at the base of and inside a short, triangular, spiniform solenomere, and an almost totally reduced leg-pair 2 in the adult female. Presumably only in already mated females, the epigynal aperture is blocked by a subquadrangular, flattened coxae 2, which suggests sexual competition. A distribution map and a detailed iconography using light and scanning electron microscopy are presented.