Exploring Ancient shellfish pathways: a morphometric perspective on the smooth scallop Flexopecten glaber

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The smooth scallop Flexopecten glaber is an endemic species of the Mediterranean Sea. From the Roman Period onwards, populations of Narbonnese Gaul made it one of the most consumed marine species along with the flat oyster Ostrea edulis (Bardot, Forest, 2013). These two seafoods have been carried to the hinterland and can archaeologically be found up to 300 km from the coast. Archaeologists are still struggling to define the routes and methods by which Romans managed to transport these shellfish in an acceptable state of freshness.The biology of the animal, until now little known because of the current scarcity of the species on the western Mediterranean coasts, holds nowadays the interest of the populations of the Adriatic and Black Sea who wish to breed it. Studies of the last decade highlighted the potential of genetic adaptation of this scallop, inducing a very great morphological diversity today. This explains the excessive creation of Mediterranean pectinids species by naturalists in the 19th-20th centuries, all of which turned out to be Flexopecten glaber (Bondarev 2018; Slynko et al. 2020; Marčeta et al. 2022).Within the framework of the DEMETER research project (ERC Starting Grant; PI A. Evin), we wished to follow the morphological diversity of scallops through Antiquity and Middle Ages (1st-12th centuries AD). Geometric morphometrics, a series of quantitative approaches for studying the shape variation of objects, has provided encouraging results for studying their diversity. Our first results show distinct shapes of smooth scallops between the lagoons of southern France, which were the main fishing grounds of the Romans. These significant differences allow us to propose a geographical origin of the hairless combs identified on archaeological sites located in the hinterland, and thus to follow the commercial routes that allowed their supply in seafood.