The giant pill-millipedes of Madagascar: revision of the genus Zoosphaerium (Myriapoda, Diplopoda, Sphaerotheriida)

All available type material of the genus Zoosphaerium Pocock, 1895, which includes 27 of 37 described species, is revised. Seven new synonyms are established: Z. stridulator (de Saussure & Zehntner, 1902) junior synonym of Z. blandum (de Saussure & Zehntner, 1902); Z. digitale (de Saussure & Zehntner, 1897) and Z. pygidiale (de Saussure & Zehntner, 1897) junior synonyms of Z. neptunus (Butler, 1872); Z. imbecillum (de Saussure & Zehntner, 1897) and Z. globulus (de Saussure & Zehntner, 1902) junior synonyms of Z. voeltzkowianum (de Saussure & Zehntner, 1897); Z. amittum Chamberlin, 1921 and Heligmasoma errans Chamberlin, 1921 junior synonyms of Z. coquerelianum (de Saussure & Zehntner, 1897). The genus Heligmasoma Chamberlin, 1921 and the subgenus Globotherium Brolemann, 1922 are both junior synonyms of Zoosphaerium Pocock, 1895. For nine species (Zoosphaerium actaeon, Z. reflexum, Z. elegans, Z. crassum, Z. stigmaticum, Z. glabrum, Z. latum, Z. lamprinum and Z. testaceum), no types could be detected in collections, so these names are to be nomina dubia. Eighteen Malagasy species are redescribed, with drawings of all structures of taxonomic importance and SEM micrographs presented here for the first time. The type material is compared with giant pill-millipede material collected during general species inventories on Madagascar conducted during the 1990s and in 2003 by different institutions, altogether comprising more than 70 morphospecies, from which eight species could be assigned to a species name. A key to Malagasy Sphaerotheriida is presented. The status of the genus Zoosphaerium is discussed. Some of the species can already be placed in preliminarily outlined species-groups.