Shell morphology and bite traces of Badister pictus A dextral shell B sinistral shell C dextral shell with an operculum D–F bite traces on dextral shells G, H bite traces on sinistral shells I broken part (shaded area) on a sinistral shell A–D, G front view E, H, I back view F dorsal view. Red circles indicate the positions where the shell (aperture) thickness was measured. Red arrows indicate the starting point of shell breaking by B. pictus. Broken lines indicate the bite traces by B. pictus.