Linking form to function: a scoping review of the evolution of paranasal sinuses in mammals.

BACKGROUND: The evolutionary origin and function of paranasal sinuses remain unclear. We investigated their presence, distribution, and drainage orientation across mammalian orders, to better understand their evolutionary development and roles. METHODOLOGY: A scoping review of anatomical, radiological, and descriptive literature was conducted in Ovid MEDLINE database (1946-2024). Data on sinus presence, type, and drainage pathways were extracted from representative species across mammalian orders. Phylogenetic (grouping by evolutionary ancestry) and phenetic (grouping by anatomical similarity) analyses were used to identify evolutionary patterns. RESULTS: Final review included 24 articles. Sinus prevalence in mammalian orders was maxillary (50%), frontal (44%), sphenoid (33%) and ethmoid (20%). Frontal sinuses were more common in behaviorally complex orders (71% vs. 22%). Frontal and maxillary sinuses predominated in terrestrial and arboreal mammals, while aquatic and volant mammals largely lacked sinuses. Phenetic clustering by sinus characteristics often contradicted phylogeny, suggesting parallel evolution driven by environment over ancestry. Despite variation in morphology, drainage pathways remained conserved. CONCLUSIONS: Paranasal sinus distribution in mammals appears more ecologically than phylogenetically determined, with convergent evolution likely influencing their presence. Conserved drainage patterns suggest developmental constraints over selective advantages. Further studies incorporating underrepresented mammalian orders and sinus size quantification are needed to refine our understanding of paranasal sinus function and evolution.