Cephalic musculature in five genera of Symphyla (Myriapoda)

The internal anatomy of the head has been investigated in representatives of five genera of Symphyla. Descriptions and schemata of the cephalic musculature, tentorial complex and other structures are displayed for two scutigerellids (Scutigerella and Hanseniella) and three scolopendrellids (Scolopendrella, Symphylella and Scolopendrellopsis). Unexpectedly, the internal anatomy of Scolopendrella corresponds to a higher degree with scutigerellids than with other scolopendrellid representatives. Symphylella and Scolopendrellopsis show features that--compared to the state in other myriapod subgroups--seem to be plesiomorphic, such as the absence of tracheae in the head, the presence of only one tentorial bridge and the presence of large dorsal muscles of the mandibular base. These states are shared with other myriapod subgroups and show that the mandibular mechanisms in Symphyla are not as specialized as previously assumed.