Abstract
Many skeletons of dogs of the Jomon period have been reported in Japan. There is little information, however, regarding medieval dogs. In 1953, the medieval burial site was excavated in Zaimokuza (Kamakura, Kanagawa Pref.). Human skeletons including 556 skulls with many of horses and dogs were unearthed there. These dogs are very important for tracing the phylogeny of the ancient Japanese dog.
We examined morphologically eight reconstructed dog skulls (six males and two females) and three other anomalous or injured skulls. The numbers of the dogs at this site was 30, as estimated by the number of lower first molars. Young dogs were rarely found at this site. Although skeletons were well preserved, many skulls were fragmented. One skull seems to have been cut by a sharp instrument such as a Japanese sword. Nearly one-third of human long bones have terminal bite injuries caused by dogs (KOHARA, 1956). They might have been killed by a sword or stick because they were eating human corpses.
The maximum cranial length of the Zaimokuza dogs (male: 170-180mm, female: 156-161mm) was longer than that of the Jomon dogs (Tagara dogs). According to the size categories described by HASEBE (1956), male dogs were of the medium type and female dogs were of the medium small type. The latter medieval dog (Kutsukake dog in the mid-sixteenth century) and early modern dogs (Asahinishi dogs and Sannomaru dogs in the seventeenth century) had similar size crania. The size of the Japanese dogs gradually became larger after Jomon period. A similar tendency was observed in North American ancient dogs by HAAG (1948). This tendency of cranial enlargement was considered to be mainly due to evolutionary changes in the Japanese dogs, and not by interbreeding with dogs imported from the other countries. The cranial enlargement continued until the Kamakura period.
The depression between the muzzle and the top of the frontal bone, the so-called stop, was slightly smaller than that of the Jomon dogs and was much smaller than that of the recent Shiba dogs. The cranial breadth and the cranial height were smaller than those of the Shiba dogs, but were similar to those in Jomon dogs. The foramen magnum showed a primitive oval form as observed in Jomon dogs. The Zaimokuza dog skeletons were very robust compared with the recent Shiba dogs. Individual variations in size and shape were greater than those in the Jomon dogs.
Many of the features of Zaimokuza dogs were similar to those in Jomon dogs, but were different from those of the late medieval and early modern dogs, especially the present Shiba dogs. In contrast to the size enlargement, the cranial proportion of the Japanese dogs was found to have changed mainly after the Kamakura period.
