the usual 30, females with 32). With these deviations from the usual 30 segments, the number of leg pairs in adults changes, usually with two leg pairs added or subtracted for each segment added to or subtracted from the typical number. For example, in Chamaesoma broelemanni, with only 26 segments (four fewer than the typical number), adult females have only 42 leg pairs, and adult males have only 40 pairs of walking legs (excluding two pairs of gonopods). Adult females with 32 segments (two more than the typical number) have 54 leg pairs (e.g., in the family Peterjohnsiidae), which is the maximum number fixed by species in the class Diplopoda. Many species deviate from the expected number of walking legs, however, because they deviate in terms of sex-linked modifications to their legs. For example, many species involve another leg pair in addition to pairs 8 and 9 in the gonopod complex in adult males. In the family Speophilosomatidae, leg pair 7 in adult males is modified as part of the gonopod complex. In many species, the gonopod complex instead includes leg pair 10 in addition to pairs 8 and 9 (e.g., Branneria carinata, Reginaterreuma monroei, Golovatchia magda, and Hoffmaneuma exiguum). The family Chordeumatidae exhibits the most extensive modifications, including five leg pairs (pairs 7 through 11) in the gonopod complex. Some species also deviate from the usual body plan by reducing or eliminating leg pairs in the adult female. In the family Chordeumatidae, for example, adult females feature a legless sternite (the "platosternite") where a third pair of legs would otherwise be. In other species (e.g., the genus Kashmireuma and the species Vieteuma longi), adult females instead exhibit modifications to their second leg pair, which are reduced to small nubbins. Distribution Chordeumatidans have a large distribution, occurring on all continents except Antarctica. They are present in Madagascar but absent from sub-Saharan Africa and, aside from southern Chile, are largely absent from South America. They occur in the tropics of Central America, Southeast Asia, and Oceania, and as far south as Tasmania, New Zealand, and Chiloé Island, Chile. They are abundant in cold, rocky, mountainous areas of Europe and central Asia, and range northward to Scandinavia, Siberia, and in North America up into Canada and southwest Alaska. Classification Chordeumatida contains approximately 1200 species, classified in four suborders and approximately 50 families, although several families contain only one to five genera. Suborder