Fig. 4.

Hypothetical scaling relationship between body size and facial length in any wild animal (white dots) and its domestic counterpart (black dots). The latter exhibit larger intragroup variation of body size and facial length, visualized via more scattering of dots along the common scaling axis (straight line). This comparison exemplifies the difference between “short snoutedness,” i.e., brachycephaly (black dots incorporated into the horizontal box), due to small size (“allometric” brachycephaly) and due to shortening of facial bones not directly resulting from small body size (“bulldog-type” brachycephaly or “katantognathic” brachycephaly). The latter is usually associated with skull modifications, including changes of facial inclination, whereas the former is not per se. Brachycephalic skull proportions may not occur in the respective wild forms. Photographs of skulls depict domestic dogs as an example (for details on specimens, see Fig. 1). The skulls are to scale.