Skeletal pathologies in extant crocodilians as a window into the paleopathology of fossil archosaurs.

Crocodilians, together with birds, are the only extant relatives to many extinct archosaur groups, making them highly important for interpreting paleopathological conditions in a phylogenetic disease bracketing model. Despite this, comprehensive data on osteopathologies in crocodilians remain scarce. Here, we present the largest osteopathological survey to date of extant crocodilian skeletal material, comprising 927 individuals and 22,281 skeletal elements spanning all three extant crocodilian families. Our results reveal 1969 osteopathologies from 414 of all individuals (44.7%). Bone trauma is the most prevalent osteopathology, representing 43.9% of all pathologies observed, followed by inflammatory lesions (27.3%) and degenerative joint disorders (11.5%). Statistical analyses demonstrate significant correlations between adult body size, ontogeny, and trauma frequency, with large-sized crocodilian species and older individuals sustaining substantially more injuries. The skull, particularly the dorsal cranial aspect, showed considerably higher involvement of trauma compared to the rest of the skeleton. We also show that non-traumatic pathologies such as inflammation and degenerative joint disorders increase in larger crocodilian species and with ontogeny. These findings underscore the behavioral and physiological drivers of skeletal disease in modern crocodilians and offer key comparative data for interpreting osteopathologies in fossil archosaurs and archosauriforms.