Morphometric Characterization of the Domestic Yak Skull (Bos grunniens Linnaeus, 1766)

This study presents a morphometric characterization of the cranial structure of Bos grunniens based on linear measurements taken from adult skulls. Twenty yak skulls (10 males and 10 females) were collected from slaughterhouses in the Bishkek region of Kyrgyzstan. A total of 27 linear cranial measurements were recorded from each specimen, focusing on neurocranial, facial, orbital, and occipital regions. The aim of this study was to describe morphological patterns and structural integration within the yak skull, and to provide baseline morphometric data for a species that remains relatively underrepresented in the literature. Correlation analyses indicated a high degree of morphological association among cranial length, width, and dental parameters. Notably, highly correlated measurement clusters were observed among total cranial length, condylobasal length, dental length, and lateral facial length, indicating coordinated growth and dimensional interdependence in the skull. The first two principal components together explained approximately 75% of the total morphometric variance. PC1 was primarily associated with global skull size and elongation, while PC2 reflected variation in orbital and frontal structures. Additionally, independent t-tests revealed statistically significant differences in selected measurements such as total cranial length, dental length, greatest mastoid breadth, greatest inner height of the orbit, and occipital heights, indicating a secondary role of sexual dimorphism in shaping cranial morphology. The findings contribute to anatomical standardization, taxonomic studies, and future comparative morphometric research in large ruminants.