关键词: 人类枕骨;早期现代人;石沟采砂场;中更新世晚期;印加骨

Abstract: In 2012, a human occipital bone fossil was discovered by Zhou Yi, from the Museum of Dingcun, in a quarry (35°45.963′ N, 111°25.310′ E) near Shigou village, Xiangfen County, Shanxi Province in North China. The quarry is located about 10 km southeast of Xiangfen County, on the west bank of the Fenhe River, at an altitude of about 412 m above sea level. It is located on the third terrace of the Fenhe River valley. According to Zhou Yi and Wang Chongfa, the quarry owner, the occipital bone was recovered from the gravel mound after the sandy gravel matrix was sifted by workers, so the fossil should be from the sand-gravel layer. Since the quarry was excavated, the stratigraphic section only retained part of the gravel layer and the underlying strata. A bunker located 104m south of the quarry that also occurred on the third terrace retained a complete section. The complete exposed strata of the quarry includes: Malan loess, reddish soil, gray silty layer, gravel layer, marly silt layer, sand-gravel layer, marly silt layer and fine sandy layer. The geological age of the sandgravel layer where the human fossil was located is late Middle Pleistocene. The fossil remains include part of the occipital squama specifically the right cerebral fossa, a portion of the left cerebral fossa, missing the basioccipital and exoccipital. A transverse suture is approximately 52.0mm at the superior border of the occipital squama and it indicates an Inca bone should exist between the parietal bones and the occipital bone. Considering the open occipital-mastoid suture and roughness of the outer surface, the occipital bone might belong to a young individual about 16~26 years of age. The wall of the cerebral fossa is about 6.5mm thick, within the range of variation in modern humans. The highest nuchal line is visible in the left part of the occipital squama, while the superior nuchal line, the highest nuchal line and the occipital torus are absent on the right side. In Homo erectus and archaic Homo sapiens fossils from China, the occipital torus is characteristic and strong developed, while the superior nuchal line and the highest nuchal line are absent. The occipital torus is absent or less developed in early modern humans, while the superior nuchal line and the highest nuchal line do exist. So the morphology of the Shigou occipital bone is more derived than Homo erectus and archaic Homo sapiens, and more similar to modern humans. It indicates that the Shigou human may belong to early modern humans. Inca bones are common in Pleistocene human fossils from China, such as Homo erectus pekinensis from Zhoukoudian and archaic Homo sapiens from Dali in Shaanxi, and from Xujiayao and Dingcun in Shanxi. This feature is also seen in early modern humans of Chuandong in Guizhou. The presence of an Inca bone at Shigou provide more evidence that the Inca bone is a regional characteristic of Pleistocene East Asians, which supports the hypothesis of continuity of human evolution in Pleistocene East Asia.

Key words: Fossil human occipital; Early modern human; Shigou Quarry; Late middle Pleistocene; Inca bone