Recovery of past species diversity and historical ecology of sawfish rostra in the Mediterranean museums and collections

Sawfishes represent one of the most critically endangered groups among elasmobranchs and have experienced local extinctions across numerous coastal regions worldwide. Contemporary conservation strategies increasingly highlight the importance of reconstructing historical changes in species distributions and geographic ranges. Within the Mediterranean, such reconstructions have indicated the historical presence of two sawfish species, presumed extinct since the 1970s, challenging earlier assumptions about their biogeographical range. In this study, we investigated whether historical sawfish specimens preserved in various institutional and private collections could provide evidence of a Mediterranean origin. A total of 229 rostra were examined, including 28 specimens labelled as originating from the Mediterranean region. Most of these samples lacked precise taxonomic classification and robust collection metadata. We performed morphometric analyses alongside mitochondrial DNA sequencing (targeting partial COI and NADH2 regions) achieving the assignment of all rostra to four extant species: Pristis zijsron (104 specimens), Anoxypristis cuspidata (52), P. pristis (47), and P. pectinata (26). Among the rostra labelled as Mediterranean, we identified P. zijsron (9), A. cuspidata (8), P. pristis (6), and P. pectinata (5). Following taxonomic identification, we implemented a preliminary isotopic approach to infer historical provenance, based on stable isotope analysis (¹³C and ¹N) of rostral teeth and collagenrich tissues from the rostra. Initial results revealed significant ¹³C variation between specimens from the Red Sea and those from other documented localities. Furthermore, high ¹N values were observed in many A. cuspidata individuals, suggesting associations with nutrient-rich, upwellinginfluenced coastal environments. The Mediterranean-labelled rostra remain tentative and require further validation through a comparison with historical baseline for elasmobranchs we are building up using the “P. Doderlein” osteological collection. These findings underscore the importance of integrating museum collections and stable isotope analyses to refine our understanding of sawfish natural history, establish historical population baselines, and could enhance global conservation planning.