Three-Dimensional Geometric Morphometric Analysis of the Ventral Sphenoid in Domestic Dogs and Cats

This study aimed to evaluate size, shape, and allometric patterns of the ventral sphenoid region in domestic dogs and cats using a three-dimensional geometric morphometric approach. A total of 45 specimens were analyzed, including 21 dogs and 24 cats. Twelve anatomical landmarks were placed on the ventral sphenoid region and analyzed following Generalized Procrustes Analysis. Shape variation was assessed using principal component analysis and permutation-based multivariate models. Dogs exhibited significantly larger centroid sizes compared to cats. A clear shape differentiation between species was detected and remained significant after accounting for size effects, indicating that interspecific differences are not solely explained by scaling. While centroid size differences among cat subgroups were not statistically significant, shape differences persisted both before and after size correction. Pairwise comparison revealed that the Scottish Fold group showed the most pronounced and consistent divergence. Allometric relationships between size and shape were significant across the entire dataset, and the interaction between size and group suggested partially distinct growth-related shape trajectories in dogs and cats. Principal component analyses indicated that the major shape variation was associated with changes in midline elongation and lateral expansion, as well as three-dimensional repositioning of midline and lateral components. These findings demonstrate that the ventral sphenoid represents a biologically meaningful basicranial module capable of capturing both interspecific differences and sizeindependent shape variation among cat subgroups.