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In this study investigates the predatory activity on a Holocene gastropod from the Argentinean Malacological Province. Buccinanops deformis (King, 1832), endemic in the southern hemisphere, is a typical taxon of cold-waters and high latitudes. We observed direct evidence of durophagy as lethal and sublethal damage. Sublethal damage was studied using traces of repaired shell as an indicator of activity by durophagous predators. Three parameters were used to evaluate durophagous predation: frequency of predation, repair scar frequency and prey effectiveness. A predatory-prey interaction was identified between Danielethus crenulatus (A. Milne-Edwards, 1879) and B. deformis during the Holocene on the Argentinean littoral coast. The low value observed for shell repair frequency (0.06), the low frequency of predation (0.16), and the intermediate value for prey effectiveness (0.37) may be interpreted because of a low but effective predatory activity. [ABSTRACT FROM AUTHOR]

Most research on bivalves from the south-western Atlantic used morphological (shell) characters for taxonomic discriminations. Dominant Veneroids from Argentinian Quaternary coastal deposits exhibit wide morphological variation – often making objective discriminations difficult/impossible, which could be objectively described and compared through geometric morphometrics techniques. This work focuses on comparison of geometric morphometrics methods applied to fossil and modern shells, to assess inter- and intra-generic variations. Three approaches were considered: landmarks (L), semi-landmarks (SL) and outlines. Shell shape analyses for different time spans (Pleistocene, fossil Holocene and modern) and areas (Patagonia and Bonaerensian) showed that Elliptic Fourier analysis (EFA), Landmarks and Landmarks plus Semilandmarks (L+SL) can discriminate at generic levels:Mactra, Mulinia(Mactridae) vs.Pitar, Protothaca, Eurhomalea, Clausinella(Veneridae). L and L+SL are powerful for inter/intraspecific distinctions ofMactra. Variability ofMactra isabelleanaincludes the remaining nominal ‘species’ (transitional morphs). Causal environmental factors of (phenotype) variation could be addressed for modern environments (substrate, salinity and energy). Subtrigonal-inflated shells predominate in muddy, quieter, shallow mixo-polyhaline waters; ovate-elongate-compressed in sandy, poly-euhaline, deeper habitats. Differential spatial distribution (and abundance) across time responds to Late Quaternary high sea-level stands: transgressive maxima allowed higher salinity in marginal-marine areas and optimal conditions forMactra isabelleanacontrasting with scarcer records in the Mar Argentino today. [ABSTRACT FROM AUTHOR]