Baculum_Landmark_Data: Landmarks were placed around the periphery of the baculum (36 sliding, 4 fixed) and relative warps (RWs) and centroid size were extracted. Landmark placement conducted using tpsDig 232 developed by Rohlf. TPS file with baculum raw landmarks for each specimen. Specimen numbers/ID can be matched with ID at the quantitative genetics data excel spreadsheet. Baculum_Repeatibility_Landmark_Data: Landmarks were placed around the periphery of the baculum (36 sliding, 4 fixed) and relative warps (RWs) and centroid size were extracted. Landmark placement conducted using tpsDig 232 developed by Rohlf. TPS file with baculum raw landmarks of a subset of the individuals. For the same individual, we have two sets of landmarks. Used to assess the repeatability of landmark placement. Specimen numbers/ID can be matched with ID at the quantitative genetics data excel spreadsheet. Female_Repeatibility_Data: Excel spreadsheet containing the vaginal measurements data for repeatability analysis, plus the identifiers of each individual. For the same individual, we have three measurements per variable measured. Used to assess the repeatability of measurement. Specimen numbers/ID can be matched with ID at the quantitative genetics data excel spreadsheet. Quantitative _Genetics _Data: Excel spreadsheet containing the male and female body weight, genital measurements, female oestrous stage, plus the identifiers of each individual and information on each individual parentage (sire and dam).

Male genitalia are among the most phenotypically diverse morphological traits, and sexual selection is widely accepted as being responsible for their evolutionary divergence. Studies of house mice suggest that the shape of the baculum (penis bone) affects male reproductive fitness and experimentally imposed postmating sexual selection has been shown to drive divergence in baculum shape across generations. Much less is known of the morphology of female genitalia and its coevolution with male genitalia. In light of this, we used a paternal half-sibling design to explore patterns of additive genetic variation and covariation underlying baculum shape and female vaginal tract size in house mice (Mus musculus domesticus). We applied a landmark-based morphometrics approach to measure baculum size and shape in males and the length of the vaginal tract and width of the cervix in females. Our results reveal significant additive genetic variation in house mouse baculum morphology and cervix width, as well as evidence for genetic covariation between male and female genital measures. Our data thereby provide novel insight into the potential for the coevolutionary divergence of male and female genital traits in a mammal.