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, 135, 149-158

Can Orbital Angle Morphology Distinguish Dogs From Wolves?

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Can Orbital Angle Morphology Distinguish Dogs From Wolves?

Luc Janssens et al. Zoomorphology.

Abstract

For more than a century, the orbital angle has been studied by many authors to distinguish dog skulls from their progenitor, the wolf. In early studies, the angle was reported to be different between dogs (49°-55°) and wolves (39°-46°). This clear difference was, however, questioned in a more recent Scandinavian study that shows some overlap. It is clear that in all studies several methodological issues were unexplored or unclear and that group sizes and the variety of breeds and wolf subspecies were small. Archaeological dog skulls had also not been studied. Our goal was to test larger and more varied groups and add archaeological samples as they are an evolutionary stage between wolves and modern dogs. We also tested the influence of measuring methods, intra- and inter-reliability, angle symmetry, the influence of variations in skull position and the possibility of measuring and comparing this angle on 3D CT scan images. Our results indicate that there is about 50 % overlap between the angle range in wolves and modern dogs. However, skulls with a very narrow orbital angle were only found in wolves and those with a very wide angle only in dogs. Archaeological dogs have a mean angle very close to the one of the wolves. Symmetry is highest in wolves and lowest in archaeological dogs. The measuring method is very reliable, for both inter- and intra-reliability (0.99-0.97), and most skull position changes have no statistical influence on the angle measured. Three-dimensional CT scan images can be used to measure OA, but the angles differ from direct measuring and cannot be used for comparison. Evolutionary changes in dog skulls responsible for the wider OA compared to wolf skulls are mainly the lateralisation of the zygomatic process of the frontal bone. Our conclusion is that the orbital angle can be used as an additional morphological measuring method to discern wolves from recent and archaeological dogs. Angles above 60° are certainly from recent dogs. Angles under 35° are certainly of wolves.

Keywords: Archaeology; Dog; Morphology; Orbital angle; Wolf.

Figures

Fig. 1
Fig. 1
OA as depicted in the original Studer (1901) publication (Figure 1, p. 4). The skull is seen from rostral view. Left dog, right wolf skull. The OA is the dorsal angle between a horizontal leg on top of the frontal bones and tan oblique leg. The oblique leg can be drawn in two different ways: the dorsal contact point is identical in both (ZP), and the ventral contact point is the most lateral structure of two points to come in contact with “the measuring plane”. This ventral point can be the most dorsolateral point of the zygomatic arch (ZA) as in the dog skull, or the FP as shown in the wolf skull
Fig. 2
Fig. 2
Horizontal line on top of the frontal bones represents the first leg of the angle. The oblique leg of the angle can be drawn in two ways: the dorsal contact point is stable (ZP) and the ventral contact point is the most lateral structure to contact “the measuring plane”, this is either ZA (as in this skull) or FP
Fig. 3
Fig. 3
Lateral skull view. The almost vertical line represents the oblique leg of the OA when FP and ZP are contact points. The almost horizontal line represents the oblique leg of the OA when FP and ZA are contact points
Fig. 4
Fig. 4
A 3D CT model reconstruction of a wolf skull in the OsiriX MD software program. Rostral view
Fig. 5
Fig. 5
Block diagram of the mean OA and spread in recent and archaeological dogs and wolves

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