1. Associated to the cranium, 88 homologous muscular units can be distinguished in Testudines (Appendix 1).
2. The basis of the new nomenclatural system for cranial muscles in turtles takes into account the connections among muscular units and the plasticity and hierarchical nature of muscle development and evolution.
3. As in all vertebrates, the n. trigeminus (V) and the n. facialis (VII) innervated muscles are the best-studied muscular structures in turtles. Cranium-associated structures of the nose, the eye, the tongue, or the neck region are rarely described for particular species.
4. The crucially different arrangement of mm. adductor mandibulae externus among all major tetrapod groups – Lissamphibia, Mammalia, Sauria, Testudines – suggests an independent, non homologisable differentiation of those muscular structures in evolution. This could imply a position for turtles outside all remaining living
Reptilia. I cannot test based on my exclusively neontological data whether Testudines evolved within one of the fossil ""Anapsida"-clades or on the stemline of Sauria within Diapsida.
5. A sister group relationship of Testudines + Archosauria could be supported by the presence of an n. abducens (VI) innervated m. pyramidalis (No. 35) and by a derived pattern of jaw muscle development: autapomorphically m. adductor mandibulae internus et posterior are closely related to each other.
6. A sister group relationship of Testudines + Lepidosauria on the other hand, could be supported by the shared tendency to derive intramandibular musculature from the m. adductor mandibulae internus Anlage.
7. Due to highly derived neck bending mechanisms, both Pleurodira and Cryptodira show a particular anatomy of the anterior neck muscles leading to confusions about the epaxial or hypaxial identity of the respective structures. Mainly based on considerations regarding the innervation pattern, I was able to asign each singular structure to either one or the other region.
