The dogs of Roman Vindolanda, Part III: Quantifying juvenilization and pleiotropic effects of miniaturization

In this report we focus on harriers, small dogs of gracile build widely represented in Roman artwork, yet not previously documented from skull or skeletal material. With them we compare remains of other types of small dogs from Vindolanda and other Roman-era sites. Accurate characterization of small dogs requires differentiation between paedomorphy and juvenilization in skull ontogeny. We present a new method for quantifying the degree of juvenilization in dog skulls which is based on understanding the differential development of endochondral and dermal centers of ossification. We enumerate functional and pleiotropic effects of skull and dental morphology and development that are characteristic of miniature dogs but rare in dwarf dogs and in large, normally-proportioned dogs. By comparing a wide array of modern dogs and wolves, we determine the degree to which small gracile dogs of the Roman era differ from primitive, non-juvenilized forms. We employ ratio analysis of dog skull shape utilizing parameters previously indicated by principal component analysis (PCA) as being of high diagnostic value. Although some small and medium-sized domestic dogs have highly juvenilized skulls, equally small skulls from Vindolanda are no more juvenilized than wolves or Dingoes. While small, gracile dogs existed as early as the late Iron Age, we conclude that juvenilization in dogs arose after the Roman era.