Can orbital angle morphology distinguish dogs from wolves?

Area of Science:

• Zoology
• Paleontology
• Forensic Anthropology

Background:

• The orbital angle (OA) has historically been used to differentiate dog and wolf skulls.
• Previous studies reported distinct OAs for dogs and wolves, but recent research indicates overlap.
• Methodological limitations and small sample sizes in prior studies necessitated further investigation.

Purpose of the Study:

• To re-evaluate the orbital angle as a distinguishing feature between wolves and dogs using larger, more diverse samples, including archaeological specimens.
• To assess the influence of measurement methods, reliability, skull positioning, and 3D CT scans on OA measurements.
• To explore evolutionary changes in skull morphology contributing to OA differences.

Main Methods:

• Measurement of orbital angles in large, varied groups of modern wolves, modern dogs, and archaeological dog skulls.
• Assessment of measurement reliability (intra- and inter-observer) and the impact of skull positioning.
• Comparison of direct measurements with those obtained from 3D CT scan images.
• Analysis of skull morphology, specifically the lateralization of the zygomatic process of the frontal bone.

Main Results:

• A significant overlap (approximately 50%) exists between wolf and dog orbital angle ranges.
• Extremely narrow OAs were exclusively found in wolves, while very wide OAs were unique to dogs.
• Archaeological dogs exhibited mean OAs close to wolves, with lower symmetry compared to wolves.
• Measurement methods demonstrated high reliability, and minor skull position variations had minimal impact.
• 3D CT scans provided measurable angles but were not directly comparable to direct measurements.

Conclusions:

• The orbital angle serves as a valuable additional morphological method for distinguishing wolves from recent and archaeological dogs.
• Orbital angles above 60° are indicative of recent dogs, while angles below 35° strongly suggest wolves.
• Evolutionary divergence, particularly the lateralization of the frontal bone's zygomatic process, contributes to the wider OA in dogs.