RECONSTRUCTION OF THE ADDUCTOR CHAMBER AND BITE FORCE IN PTERODACTYLOIDS (ARCHOSAURIA, PTEROSAURIA)

The reconstruction of jaw muscles is critical in establishing potential cranial functions and investigate signals of potential dietary habits. However, myological studies concerning extinct groups that left no extant representatives are hard to perform and difficult to test. This is particularly true for pterosaurs, which exhibit a plethora of cranial variation, suggesting different functions and feeding habits. We present here the first attempt to reconstruct in detail the adductor musculature of the pterodactyloid mandible under the extant phylogenetic bracketing method. Reconstruction of the mandibular musculature, in turn, allows for the estimation of muscle cross-sectional area. Subsequently, this permits to present bite force estimations for selected species: _Tapejara wellnhoferi_, _Caupedactylus ybaka_, _Tupuxuara leonardii_, _Thalassodromeus sethi_, _Dsungaripterus weii_, _Anhanguera blittersdorffi_, _Tropeognathus mesembrinus_, _Pteranodon longiceps_ and _Nyctosaurus gracilis_. However, as this dataset comprises species of various body sizes and as bite forces correlate allometrically with body size, absolute values of bite force are of limited comparative value. For this reason, we further estimate bite force quotients (BFQ) which are generated from the residuals of regression between absolute bite force and body mass. Body masses were estimated following a method available in the literature, a correlation between stylopodial circumferences and body mass. As a result, _Pteranodon_, _Nyctosaurus_ and anhanguerids are found to exhibit relatively weak but fast bites with relatively low mechanical advantages and BFQs, corroborating their view as piscivores. However, we further suggest that, among those, _Tropeognathus mesembrinus_ was specialized in consuming relatively larger prey compared to _Anhanguera_. We corroborate the view of _Dsungaripterus_ as a durophage and propose that _Thalassodromeus_ shared such feeding habit, estimating for both taxa the highest BFQs and absolute bite force values. We also corroborate the interpretation of _Tapejara wellnhoferi_ as a specialized consumer of hard plant material, with a relatively high BFQ and the highest mechanical advantage among the analyzed taxa. We propose that _Caupedactylus ybaka_ and _Tupuxuara leonardii_ were ground-feeding generalists with their intermediate bite force values and less specialized jaws. With the diversity of dietary preferences of pterosaurs being still relatively under-investigated, we hope the present study will serve a basis for future progress. [CAPES 1845438].