Melanoides tuberculata and Zootecus insularis gastropod shells provide a snapshot into past hydroclimatic conditions of arid environments: New perspectives from Oman

Shells of the aquatic gastropod Melanoides tuberculata and the terrestrial gastropod Zootecus insularis were analysed using high-resolution isotope sampling (up to 274 samples per shell) to assess their potential use as a proxy for hydroclimatic and palaeoenvironmental reconstruction in drylands. A total of 169 snails (fossil and modern) were collected from 37 sites in Northern Oman and Dhofar, with each site selected for its specific geomorphological, archaeological or ecological context. This included fluvial terraces, playa environments, modern oasis gardens, irrigation channels and Neolithic (6000–3200 BCE) and Early Bronze Age (3200–2000 BCE) archaeological sites. The δ 18 O data obtained from these gastropods could be classified into eight different patterns, three for the aquatic snails (Type 1 A–C) and five for the terrestrial snails (Type 2 A–E), which were linked to the environmental context of their habitat. Furthermore, the use of the aquatic snails enabled us to distinguish between groundwater and surface water signals, whereas the terrestrial snails were employed to reconstruct changes in rainfall origin, humidity, evaporation, regular wet-dry cycles, and/or the presence of meteorological events such as cyclones. According to the results, gastropods can be used to elucidate the long-term, local evolution of rain-fed floodplain ecosystems in drylands and to identify the hydrological resources present in the vicinity of archaeological sites, particularly with regard to type (e.g. , surface water vs groundwater). • Stable isotope values of snails offer insights into hydroclimatic history of drylands. • Isotopic data differentiate eight distinct environmental signals in gastropod shells. • Gastropods provide a snapshot into Neolithic and Bronze Age environment. • Aquatic snails' δ 18 O values highlight their potential in geoarchaeological research.