Myriapod groups with differences in dorsal and ventral segmentation. (A) A male Scutigerella immaculata (Myriapoda: Symphyla). Note the different number of dorsal units (15 tergites) and ventral units (twelve pairs of trunk legs). (B) Specimen of Pauropus huxleyi (Myriapoda: Pauropoda). Note that nine pairs of trunk legs are present, contrasting with only seven tergites (including anal plate). Both species are shown in dorsal aspect, anterior to the left. After .