The use of the Hartigan's Dip Test for unimodality provides a novel tool in the detection of sexual dimorphism in shell characteristics in marine gastropods. A sample of 88 Doxander queenslandicus Maxwell, 2022 from Aru Island Indonesia collected in August 2026, was used to test for axial length modality. Axial length bimodality is an indicator for sexual dimorphism within a population. The results indicated that there were two distributions in axial length data (D=0.058052, p=0.0245) and construction of these mirrors research findings and theoretical modelling for sexual dimorphism in Strombidae. This study provides an example for the testing of larger single dry samples in research institutions. This information can be used to determine shifts in size dynamics within populations through time by detecting the effects of shifts in climate or size specific collecting practices.