Prey selection, size, and breakage differences in <em>Turbo undulatus</em> opercula found within Pacific Gull (<em>Larus pacificus</em>) middens compared to Aboriginal middens and natural beach deposits, southeast Australia

Qualitative discrimination criteria are employed commonly to distinguish cultural shell middens from natural shell deposits. Quantitative discrimination criteria remain less developed beyond an assumption that natural shell beds tend to contain a wider range of shell sizes compared to cultural shell middens. This study further tests this assumption and provides the first comparative quantitative analysis of shell sizes from cultural middens, bird middens, and beach shell beds. Size distributions of opercula of the marine gastropod Turbo undulatus within two modern Pacific Gull (Larus pacificus) middens are compared with two Aboriginal middens (early and late Holocene) and two modern beach deposits from southeast Australia. Results reveal statistically significant differences between bird middens and other types of shell deposits, and that opercula size distributions are useful to distinguish Aboriginal middens from bird middens but not from beach deposits. Supplementary qualitative analysis of taphonomic alteration of opercula reveal similar opercula breakage patterns in human and bird middens, and further support previously recognised criteria to distinguished beach deposits (water rolling and bioerosion) and human middens (burning). Although Pacific Gulls are geographically restricted to southern Australia, the known capacity of gulls (Larus spp.) in other coastal contexts around the world to accumulate shell deposits indicates the broader methodological relevance of our study.

定性判别标准通常被用于区分文化贝丘和自然贝壳沉积。除了假定自然贝壳层相较于文化贝丘往往包含更广泛的贝壳尺寸范围外，定量判别标准还不太完善。本研究进一步检验了这一假定，并首次对文化贝丘、鸟类贝丘和海滩贝壳层的贝壳尺寸进行了比较定量分析。将两个现代太平洋鸥（太平洋鸥）贝丘内的海洋腹足纲动物波纹唇螺厣的尺寸分布与两个原住民贝丘（全新世早期和晚期）以及澳大利亚东南部的两个现代海滩沉积进行了比较。结果显示，鸟类贝丘与其他类型的贝壳沉积之间存在统计学上的显著差异，并且厣的尺寸分布有助于区分原住民贝丘和鸟类贝丘，但无法区分原住民贝丘和海滩沉积。对厣的埋藏学变化的补充定性分析显示，人类贝丘和鸟类贝丘中厣的破损模式相似，并进一步支持了先前已被认可的区分海滩沉积（水流滚动和生物侵蚀）和人类贝丘（火烧）的标准。尽管太平洋鸥在地理上局限于澳大利亚南部，但世界其他沿海地区的鸥（鸥属）积累贝壳沉积的已知能力表明我们的研究在方法学上具有更广泛的相关性。