Allometric patterns in Rhamphorhynchus muensteri and their role in the paleoecology, life habits, and taxonomic framework of pterosaurs.

Pterosaurs were the first vertebrates to achieve powered flight, a result of various unique anatomical adaptations, and significant morphological diversity throughout their evolutionary history. Although the pterosaurs body structure was specialized for powered flight, the clade exhibited great disparity from its origins, with later evolution giving rise to multiple phylogenetic lineages and a wide range of body sizes, from small forms such as Anurognathus ammoni to truly giant species like Quetzalcoatlus northropi. This variation led to distinct flight strategies within the group. Here, we assess allometry in the skeletal elements of Rhamphorhynchus muensteri in comparison with Eupterodactyloidea and Euctenochasmatia, examining their implications for paleoecology and flight capacity. The analysis included 127 specimens and assessed 13 skeletal variables using statistical methods, principal components analysis (PCA), and standardized major analysis (SMA). The results reveal differences in size-shape trajectories and functional adaptations related to activity flight. R. muensteri exhibits a trend of negative allometry (PCRW/body, humerus, radius/ulna, metacarpal IV, and femur), indicating distinct allometric scaling patterns and flight style. These patterns suggest behavior and ecological differences, as well differing flight capabilities between R. muensteri likely relied on active flapping flight interspersed with gliding, whereas other taxa may have exhibited greater migratory adaptations within Eupterodactyloidea, and a greater dependence on flapping flight in Euctenochasmatia. The negative allometry in R. muensteri suggests a flight style characterized by early flight capability (precocial flight), whereas Eupterodactyloidea showed positive allometry and Euctenochasmatia isometry. Additionally, the study highlights how allometric patterns influence pterosaur phylogeny, underscoring the importance of incorporating them into future analysis.