Flesh and bone: The musculature and cervical movements of pterosaurs.

Abstract

The osteological variations present in the cervical vertebrae of pterosaurs represent changes in the soft tissues of the neck and reflect their function. Here, we infer the presence, volume, and capacity of the cervical musculature of pterosaurs. We performed our analyses on three-dimensionally preserved cervical series of Anhanguera sp. (AMNH 22555), Anhanguera piscator (NSM-PV 19892), Azhdarcho lancicollis (ZIN PH and CCMGE, several specimens), and Rhamphorhynchus muensteri (MGUH 1891.738), the last three of which were digitally modeled for muscle reconstruction. We identified osteological correlates from structures observed in extant archosaur vertebrae and skulls and supported by Extant Phylogenetic Bracket (EPB) criteria. We estimated the muscular capacity using the "Maximal Force Production" formula. According to our analyses, at least thirteen muscles were present in the neck of pterosaurs, only one of which does not correspond to an EPB level I inference. The muscles that performed skull and neck pitching were more robust and stronger to execute the movements. Muscles that showed extremely low potential had a more cervical stabilization function. Specializations we identified in the muscles are compatible with the foraging habits previously inferred for these pterosaurs, namely surface fishing by Rhamphorhynchus and Anhanguera and capture of small terrestrial prey by Azhdarcho.