Abstract
This is the first full description of an infant Jomon (Neolithic) skeleton, which was excavated in 1982 from the Usuiso shell-mounds site in Fukushima Prefecture, northeast Japan. Archeologically the shellmounds are presumed to be formed mainly in the Latest Jomon period.
The age of this skeleton was estimated at about 10 years based on the sequence of permanent tooth eruption. Its sex is unknown. Compared to the average adult, the relative sizes of the bones were smaller; 90-100% in the braincase, 80-90% in the face, 70-80% in the postcranials.
The overall shape of the skull conforms to those of present day infant skulls ; the cranial vault is round and the face is low. However, this skull already exhibits some of the typical features of adult Jomon skulls ; such as a prominent glabella (to a slight degree), a thick frontal process of the maxilla, and a wide mandibular ramus. In addition, it has rectangular orbits and a marked alveolar prognathism, which differ from those of the adult Jomon skulls. These two characteristics might indicate a tentative condition common during the childhood.
Although most of the limb bones are strikingly slender, the fibula is rather robust having marked muscle reliefs, which implies strong leg muscles. The humerus and the fibula show marked diaphyseal flatness as seen in most Jomon adults, but the femur and the tibia do not. In the arm the lower segment is relatively long as in most Jomon adults. In the leg, unlike most Jomon adults, the lower segment is relatively short. The so-called squatting facets on the neck of the talus are well developed showing habitual squatting.
