Revision of some of the oldest species in the millipede genus Sphaerotherium Brandt, 1833 (Diplopoda, Sphaerotheriida, Sphaerotheriidae), with new synonymies

During a study of Sphaerotherium samples from South Africa, the underside of the posterior margin of the tergites was found to yield some important taxonomic characters that appear remarkably stable both in the male and female, as well as between stadia and tergites. The opportunity is taken here to revise most of the oldest Sphaerotherium species, with special reference to the structure of the posterior tergal margin. All available type material of the species described by Brandt, Gervais, C. L. Koch, Porat and Karsch have been revised, with the following synonymies established or confirmed: S. klugii Brandt, 1841, S. repulsum Karsch, 1881, S. trichopygum Attems, 1908 and S. ancillare Attems, 1928 = S. compressum Brandt, 1833; S. microstictum Brandt, 1841 = S. elongatum Brandt, 1833; S. retusum C. L. Koch, 1847 = S. dorsale Gervais, 1847, and S. grossum C. L. Koch, 1847 = S. obtusum C. L. Koch, 1847. As the subgenera Neobournellum Attems, 1908 and Tetraconosoma Verhoeff, 1924 appear to be strict junior subjective synonyms of Sphaerotherium s. str., to replace Sphaerotherium auct. the genus-group name Bournellum De Saussure & Zehntner, 1902 is revived as currently the earliest available substitute, with the type species Sphaerotherium retusum C. L. Koch, 1847 showing ≥7 sensory cones on the last antennomere. A neotype of Oligaspis puncticeps Wood, 1865 has been selected, and the species is shown to be a new junior subjective synonym of S. rotundatum Brandt, 1833.