Transport of seashells through Gallia Narbonensis: Archaeobiogeography, provenance and trade of smooth scallop Flexopecten glaber revealed through geometric morphometrics

The smooth scallop ( Flexopecten glaber ) is a seafood that was widely consumed in Gallia Narbonensis (Southern France) during Roman times. Harvested from lagoons along the Mediterranean coast, the species was transported to consumers up to a hundred kilometres from the seashore. However, the origins of this fresh produce supplied to the Gallo-Romans remain largely unknown. The variation in size and shape of 1149 shells originating from 27 archaeological sites in Southern France, dating from the 1st c. BC to the 12th c. AD, was quantified using Elliptic Fourier Transforms and analysed through geometric morphometrics. The morphometry of scallop shells is highly structured geographically, showing differences between lagoons of origin regardless of the period. This archaeobiogeographical pattern allows for the estimation of the geographical origin of valves discovered in the hinterland and the reconstruction of marine resource provisioning centres. While most valves were sourced as close as possible to the place of consumption, the exception of the smooth scallops from the city of Nemausus (Nîmes) reveals a structured network dedicated to urban supply. Future research could extend these methodologies to a broader geographical scope, providing a more detailed analysis of trade and supply networks of Mediterranean shellfish. • Smooth scallop right valves vary in size and shape over time and lagoons. • 75% of the valves can be attributed to their correct lagoon based on shape. • Hinterland valves' origin can be inferred from the coast's geographical structure. • Geometric morphometrics is a new tool for exploring trade of ancient seashells.