Shell strength of freshwater molluscs and its implication on preservation potential

Shell strength of the modern freshwater molluscs Heleobia parchappii, Biomphalaria peregrina, Uncancylus concentricus, Musculium argentinum, Physa acuta, Succinea meridionalis and Pomacea canaliculata was quantified through load measurements and analysed using Weibull distribution, a statistical met...

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Bibliographic Details
Published in:Historical biology 2021-11, Vol.33 (11), p.2668-2682
Main Authors: Cristini, Paula Andrea, Frontini, Patricia Maria, Ballarre, Josefina
Format: Article
Language:English
Subjects:
Aragonite
Brittle materials
Compressive strength
freshwater
Load distribution
Mollusca
molluscs
Mollusks
Organic matter
Sediments
Shell strength
Shells
Statistical analysis
Statistical methods
taphonomy
Weibull
Weibull distribution
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Summary:Shell strength of the modern freshwater molluscs Heleobia parchappii, Biomphalaria peregrina, Uncancylus concentricus, Musculium argentinum, Physa acuta, Succinea meridionalis and Pomacea canaliculata was 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, being P. canaliculata (biovolume = 10 4 mm 3 ) the largest and H. australis and H. 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 of H. parchappii in death and fossil assemblages from Pampa sediments.
ISSN:0891-2963
1029-2381
DOI:10.1080/08912963.2020.1822355