The presence of cockle shells in Mesolithic and Neolithic Portuguese archaeological sites located near the coast or estuaries is relatively common. Here we report the study of a collection of complete and fractured Cerastoderma edule (Linnaeus, 1758) shells (with umbo) recovered from a well-preserved midden dated from Late Mesolithic found at the São Julião archaeological site, unit C (Mafra, Portugal).

In order to interpret the main morphological alterations observed in the archaeological shells, these were compared with modern specimens from alive animals and dead molluscs present in thanatocoenosis along the Portuguese coast, and also with shells experimentally subjected to overburden in soil.

It was observed that shells from dead molluscs collected in thanatocoenosis present wear all over the surface and especially in the umbo region with the formation of a hole, which was not observed in the archaeological shells. Fractured archaeological shells resembled modern shells fractured by overburden in the laboratory. Experimentally, shells were found to be very resistant to fracture, requiring high pressure to be exerted from above the burial soil in order to crack. In usual conditions, this would correspond to a layer of soil over 20 m high, much higher than conditions that existed at the São Julião archaeological site.

It was concluded that cockle shells studied in the present work were collected alive and probably consumed as food. Their fracturing was post-depositional, occurred during burial and was probably determined by the pressure exerted by a house of brick and cement that had existed above the archaeological site.

在位于海岸或河口附近的中石器时代和新石器时代葡萄牙考古遗址中，海扇贝壳的存在相对普遍。在这里，我们报告了对一组完整的和断裂的Cerastoderma edule（Linnaeus，1758 年）贝壳（带有 umbo）的研究，该贝壳是从 São Julião 考古遗址 C 单元（葡萄牙马夫拉）发现的中石器时代晚期发现的保存完好的贝壳中发现的.

为了解释在考古贝壳中观察到的主要形态变化，将这些贝壳与葡萄牙海岸沿线灭亡群落中存在的活动物和死软体动物的现代标本进行了比较，还与在土壤中经受过覆盖试验的贝壳进行了比较。

据观察，在灭亡中收集的死软体动物的贝壳在整个表面，特别是在 umbo 区域，形成了一个洞，这在考古贝壳中没有观察到。破碎的考古贝壳类似于实验室中被覆盖物破坏的现代贝壳。实验发现，贝壳具有很强的抗断裂性，需要从埋土上方施加高压才能破裂。在通常情况下，这对应于超过 20 m 高的土壤层，远高于 São Julião 考古遗址的条件。

得出的结论是，本研究中研究的海扇壳是活的，可能作为食物食用。它们的破裂是沉积后的，发生在埋葬期间，可能是由存在于考古遗址上方的砖和水泥房屋施加的压力决定的。