摘要 : Shell strength of the modern freshwater molluscsHeleobia parchappii, Biomphalaria peregrina, Uncancylus concentricus, Musculium argentinum, Physa acuta, Succinea meridionalisandPomacea canaliculatawas quantified through load measu... 展开 Shell strength of the modern freshwater molluscsHeleobia parchappii, Biomphalaria peregrina, Uncancylus concentricus, Musculium argentinum, Physa acuta, Succinea meridionalisandPomacea canaliculatawas quantified through load measurements and analysed using Weibull distribution, a statistical method used for brittle materials. In this study, we defined shell strength as the maximum compressive force required to break a shell per unit of resistant area, which is known as mechanical tension or stress. Intrinsic properties of shells were also measured through mineralogical and morphological characterisation. Shells were mainly composed of aragonite and varied in size and shell thickness, beingP. canaliculata(biovolume = 10(4)mm(3)) the largest andH. australisandH. parchappii(3.35 and 7.93 mm(3), respectively) the smallest ones. The dominant microstructure was cross-lamellar, with layers that varied between one and four. The organic matter of the matrix varied between 1.58% and 4.24%. Shell strength differs among mollusc species. Smallest species have higher shell strength than larger ones because they have a smaller resistant area on which the load is applied, and therefore the resulting value of fracture stress increases abruptly. This may explain the dominance ofH. parchappiiin death and fossil assemblages from Pampa sediments. 收起