Morphometric analysis of limpets from an Iron-Age shell midden found in northwest Portugal

Abstract

The present work reports an analysis of a shell midden found in Terroso hillfort, an important Iron-Age oppidum located in northwest Portugal. The midden was dated from the latest phase of occupation of the hillfort, between the Ist century BC and the Ist century AD (Roman period), and contained 684 well-preserved Patella shells. The identification of archaeological shells was carried out comparing them with modern specimens collected in two shores in the neighborhood of the hillfort. The identification of modern shells was based on radula pluricuspid teeth and shell morphology. Relative abundance of Patella species in the Terroso midden was different from modern populations. Archaeological shells were dominated by Patella vulgata, but Patella intermedia was the most abundant species in modern populations. Dimensions of archaeological shells were very different from modern populations. Shell length range and variability in archaeological shells were lower than in the modern populations. Log height vs. length plots for archaeological shells were different from modern populations. Patella shells from Terroso midden was significantly taller then modern specimens. These differences between archaeological shells and modern populations could be due to environmental changes, namely an increase in wave action and intensity. These harsher costal conditions could have resulted from an alteration in the morphology of the coast, caused by a rise in the mean sea level from 2000 years BP to the present. Alternatively or additionally, the observed differences can be related to gathering strategies. Archaeological shells could have been selected by size, and collected preferentially at high shore and in sheltered sites.