Shape variation of linea temporalis and crista nuchae in mesocephalic dogs

İngilizce (OpenAlex)

Dog domestication began around 40,000 years ago in Eurasia, following their divergence from grey wolves. Once domesticated, dogs were selectively bred for functions such as guarding, herding, and hunting. The classification of modern breeds was later formalised in Victorian England, emphasising both morphology and working purpose. Cranial features like the linea temporalis and crista nuchae reflect this morphology and serve as critical osteological landmarks, reflecting muscle attachment, bite force, and neck stabilisation. In this study, geometric morphometric analyses were performed on 81 mesocephalic dog skulls representing five functional groups (hunting, guarding, companionship, herding, sled). Using three-dimensional models from Czeibert et al’.s study, 43 landmarks and semilandmarks were digitised along these cranial structures. Procrustes superimposition, PCA, Procrustes ANOVA, regression, and discriminant analyses were applied to evaluate shape variation, size influence, and functional differentiation. PCA revealed that most variation (PC1: 34.945%) occurred in the parietal portion of the linea temporalis and dorsal origin of the crista nuchae, with toy dogs forming a distinct cluster. Significant shape (p < 0.0001) and size (p < 0.0006) differences were found, while discriminant analysis showed partial overlap among functional groups. Overall, the study highlights how variation in these cranial landmarks reflects functional adaptation, selective breeding, and evolutionary development in domestic dogs.