Revolving SEM images visualising 3D taxonomic characters: application to six species of the millipede genus Ommatoiulus Latzel, 1884, with description of seven new species and an interactive key to the Tunisian members of the genus (Diplopoda, Julida, Julidae)

A novel illustration technique based on scanning electron microscopy is used for the first time to enhance taxonomic descriptions. The male genitalia (gonopods) of six species of millipedes are used for construction of interactive imaging models. Each model is a compilation of a number of SEM images taken consecutively while rotating the SEM stage 360 degrees, which allows the structure in question to be seen from all angles of view in one plane. Seven new species of the genus Ommatoiulus collected in Tunisia are described: O. chambiensis, O. crassinigripes, O. kefi, O. khroumiriensis, O. xerophilus, O. xenos, and O. zaghouani spp. n. Size differences between syntopic adult males of O. chambiensis and O. xerophilus spp. n. from Chaambi Mountain are illustrated using scatter diagrams. A similar diagram is used to illustrate size differences in O. crassinigripes, O. khroumiriensis spp. n. and O. punicus (Brolemann, 1894). In addition to morphological differences, the latter three species display allopatric distribution and different habitat preferences. A dichotomous interactive key with a high visual impact and an intuitive user interface is presented to serve identification of the 12 Ommatoiulus species so far known from Tunisia. Updates on the North African Ommatoiulus fauna in general are presented.