IntroductIon Coastal beaches represent peculiar ecosystems where natural events linked to marine weather dynamics (waves, tide, wind, and currents) allow a massive deposition of abiotic and biotic debris (McLachlan 1983). The biotic component of marine debris deposited on sandy beaches is mainly composed by algae, plants (e.g. Posidonia oce- anica) and animals (fish, crustaceans, molluscs). In par- ticular, sandy beaches may act as trap ecosystems where it is possible to obtain approximate check-lists of the spe- cies for a study area: therefore, the analysis of their debris can provide cost-effective assessment of biodiversity for single sites and over broad spatial scales (e.g. Garcia Gomez 1983, Zuschin & Pervesler 1996, Giacobbe & Spanò 1997, Smith 2009). Marine molluscs are invertebrates widely distributed in subtidal and intertidal habitats, both on soft and hard substrates, and represent an important component of the marine debris, periodically or constantly deposited on the beaches. Specific environmental features and condi- tions (both biological and physic-chemical) may facilitate a massive aggregation of debris built by shells belong- ing to a variety of dead mollusc species (shore-based thanatocoenoses). Due to their calcareous shells, speci- mens belonging to a large number of species may be eas- ily detected with a relatively low research effort. Conse- quently, these species-rich groups are characterized by a large and consolidated taxonomic knowledge and most studies have been devoted to quantify their patterns of composition, diversity and distribution in debris contexts (e.g. Luque & Templado 1981, Warwick & Light 2002, Rose 2003, Terlizzi et al. 2005, Smith 2005, 2008, 2009) Taxonomic checklists are useful to assess the eco- logical value of an area so evidencing their conservation value and concern (Sutherland 2000). In this sense, recent thanatocoenoses obtained classifying shells of molluscs recently deposited as debris on sandy beaches (mainly represented by macro-gastropods and bivalves) may approximately represent the biodiversity of the regional fauna, and therefore can be used as a surrogate for the purpose of rapid biodiversity assessment (Warwick & Light 2002, Smith 2009; e.g. in research on climate change effects on marine biodiversity: Warwick & Turk 2002, Leonard et al. 2006). Although their dispersal along the Mediterranean coasts and the important role as sink ecosystems, there are only few studies describing recent macro-mollusc thanatocoenoses located on sandy beach- es, being mainly focused on living assemblages (e.g. Elias 1992, Terlizzi et al. 2005, Neira et al. 2014). In this study, we report the taxonomic composition and species richness of a recent macro-mollusc thanato- coenosis sampled on a Mediterranean sandy beach of Sic- ily (Southern Italy). We selected this site because of their large sandy beach, where sampling is particularly easy and consequently repeatable for future monitoring. Par- ticularly, since many studies have highlighted the strong differences in terms of species richness and composition Vie et milieu - life and enVironment, 2016, 66 (2): 191-198 CoMPoSITIoN AND DIvERSITy of A RECENT MACRo-MoLLuSC ThANAToCoENoSIS fRoM A MEDITERRANEAN SANDy bEACh (SAN vITo Lo CAPo, NoRTh-WESTERN SICILy) C. Battisti 1,* , f. Cerfolli 2 1 “torre flavia” lter (long t erm ecological research) station, Città metropolitana di roma Capitale, Protected areas service, Via tiburtina 691, 00159 rome, italy 2 department of ecological and Biological sciences (deB), ichthyogenic experimental marine Centre (Cismar), tuscia university, Borgo le saline, 01016 tarquinia, Viterbo, italy * Corresponding author: c.battisti@cittametropolitanaroma.gov.it AbSTRACT. – Despite their diffusion along the Mediterranean coasts, recent shore-based dead mollusc assemblages (thanatocoenoses) have been poorly studied in their structure and compo- sition. here we report data on composition and structure of a recent macro-mollusc thanato- coenosis (Gastropoda and bivalvia, size > 2 mm) sampled on a Mediterranean sandy beach. We sampled 79 species (653 specimens), 55 of them belonging to Gastropoda (n = 466, with 8 dom- inant species) and 24 to bivalvia (n = 147, with 6 dominant species). Margalef richness index showed higher values in Gastropoda compared to bivalvia, corroborating a general pattern known for the assemblages of the Mediterranean Sea. Whittaker plot and Preston diagram dis- played the differences in diversity between these two orders. Probably the high heterogeneity of local substrates provides a large suitability of habitats and niches for these mollusc assemblages, so explaining these different patterns. Although analyses of thanatocoenoses have some limita- tions, these data might be used for biodiversity assessments, useful for future monitoring using comparable methods and research effort. MoLLuSC ASSEMbLAGE ThANAToCoENoSIS GASTRoPoDA bIvALvIA MARGALEf INDEx WhITTAkER PLoT PRESToN DIAGRAM