Purely by chance, as she happened to be on holiday in the South of France at the time, and knowing my involvement in the discovery of Papillifera bidens (formerly Papillifera papillaris) at Cliveden, Buckinghamshire (Ridout Sharpe, 2007), a friend sent me a cutting from the local newspaper which she thought might interest me: ‘Un escargot prisonnier des arènes depuis 2000 ans’ (L’Independant for Languedoc Roussillon, 29 April 2009). The ‘arènes’ refers to the Roman arena or amphitheatre at Nîmes – and the snail is another clausiliid, Leucostigma candidescens, which bears an uncanny resemblance to P. bidens, right down to the necklace of little white spots along the suture line. Is there any connection between these two species? Yes, insofar as both of these snails had been transplanted from their home territory through the agency of man and have managed to survive in, but not spread out from, their new localities. Each correlates with a specific event in the past and provides a tiny piece in the vast jigsaw of historical and archaeological reconstruction.
Both clausiliids originated in Italy where Leucostigma candidescens has an even more restricted distribution than Papillifera bidens, being confined to the Apennines between Umbria and Campania (Fechter and Falkner, 1990). It is believed to have been transported to Nîmes by the Romans, hidden in crevices within the building stone that they imported from Italy in order to create their splendid amphitheatre during the 1st century AD. And there the snail has remained for nearly 2000 years; it has not spread beyond the amphitheatre and it is not known to occur anywhere else in France. Whereas P. bidens, which was imported into Britain from Rome in 1896 hidden in the nooks and crannies of the elaborately carved marble Borghese Balustrade, remained undiscovered at Cliveden for over 100 years, L. candidescens was not recorded in the amphitheatre at Nîmes until 1903, after nearly 1900 years of anonymity! Its survival at this site is truly remarkable, since the arena became filled with housing during the medieval period, was restored as an amphitheatre by Napoleon, and was then remodelled as a bullring in 1863 (Mienis, 2009).
Both Leucostigma candidescens and Papillifera bidens appear to have very limited powers of dispersal, and in their natural habitat are found on calcareous rocks that provide the calcium for their shells and support the algae and lichens on which they feed. In both cases, the transplanted snails have remained virtually restricted to the very material on which they were originally imported. Further study of the distribution of these clausiliids may throw light on the movement of building stone in the past. For example, P. bidens is found today in Istanbul, Turkey, where it is believed to have been introduced during the reign of Constantine the Great around AD 330 when stone was imported for the rebuilding of Constantinople. Subsequently, as this building stone was reused, P. bidens found its way into two medieval forts, and an Armenian monastery on an island in the Sea of Marmara (Örstan, 2006). I have found it among the ruins of Carthage in northern Tunisia, which was rebuilt by the Romans in the aftermath of the Punic Wars, and Menez (2007) has described its introduction into the Garrison Library Gardens in Gibraltar on garden ornaments in the 18th century AD.
Snails have been introduced into new localities for as long as man has been transporting the commodities – be they plant material, building stone or whatever – in which they naturally occur, and some may have been deliberately taken to new areas as a convenient source of food. With time, some of these ‘alien’ snails have expanded out from their points of introduction and have become naturalised, forming part of the native fauna. Helix pomatia, the eponymous ‘Roman snail’ and its smaller relative Cornu aspersum were both almost certainly introduced into Britain by the Romans from their Mediterranean homeland; both species are edible. When the shells of these snails are found in archaeological deposits, these deposits cannot predate the Roman period. Several other smaller species of snails are believed to have arrived in this country at various times between the neolithic and the present day (Davies, 2008). Most of these were probably accidental introductions although some of them, such as Theba pisana, are still eaten in their native Mediterranean countries. Establishing the time of arrival and dispersal of these different species is difficult and dependent on well-dated contexts, but in cases where this has been done these snails can provide important dating evidence. For example, the chalk hill figure known as ‘The Long Man of Wilmington’ on the South Downs near Hastings was long thought to have been made in prehistoric times. The discovery, beneath the chalk debris produced during its construction, of two species of Mediterranean origin (Candidula intersecta and Cernuella virgata) which are not known to have occurred in southeast England prior to the medieval period, has now dated this hill figure firmly to the postmedieval (Martin Bell, pers. comm.). This process continues to the present day, the most notable example being the recent and continuing expansion of Hygromia cinctella away from its point of introduction in South Devon, where it is believed to have arrived from southern Europe in the 1950s.
The presence of non-native species in archaeological shell assemblages can indicate human population movements, invasions, the spread of agriculture and the dispersal of crop plants, ancient trade routes, and the importation of specific goods and materials. Archaeomalacology is a relatively new discipline which is now expanding rapidly, and covers such diverse aspects as the use of land snail assemblages to describe past environments, the reconstruction of ancient diets from shell midden deposits, the analysis of oxygen isotope ratios to model seawater temperatures in the past, the use of shells as personal ornaments and ritual objects and hence as indicators of cognitive development in early humans – and many other things besides. The Archaeo+Malacology Group Newsletter, which was established through the pages of this magazine’s predecessor nine years ago (Ridout Sharpe, 2000: 385) includes short articles, reports and abstracts of papers on all aspects of archaeomalacology, and welcomes new contributions. Issue number 15 was published online in June 2009; this and previous issues are freely available both on the website of the ICAZ (International Council for Archaeozoology) Archaeomalacology Working Group (http://triton.anu.edu.au/) and the personal website of Aydın Örstan (http://home.earthlink.net/~aydinslibra ry/AMGnews.htm).
References
Davies, P. 2008. Snails: archaeology and landscape change. Oxford, Oxbow Books.
Fechter, R. and Falkner, G. 1990. Steinbachs Naturführer: Weichtiere. München, Mosaik Verlag.
Menez, A. 2007. Papillifera papillaris (Müller, 1774) in Gibraltar. Mollusc World, No. 14: 6-7.
Mienis, H.K. 2009. Leucostigma candidescens in the Roman amphitheatre of Nîmes, France (Gastropoda, Clausiliidae). Archaeo+Malacology Group Newsletter, No. 15: 6-7.
Örstan, A. 2006. The clausiliid snail Papillifera papillaris in Istanbul, Turkey. Archaeo+Malacology Group Newsletter, No. 9: 6-7.
Ridout Sharpe, J. 2000. Shells from the ancient Aegean. Conchologists’ Newsletter, No. 154: 379-385.
Ridout Sharpe, J. 2007. Papillifera papillaris (Müller, 1774) in Britain: a giant leap for a small snail. Mollusc World, No. 14: 12-14.
Illustration: Leucostigma candidescens (photo reproduced with kind permission of Marcus Coltro, © Femorale) on a background of a rendered image of the amphitheatre at Nîmes (Peter Topley).