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2018-04-10 | 编辑: | 【

作者:同号文,邓 里, 陈 曦,张 贝,文 军

摘要:江西萍乡杨家湾1、 2号洞出土了40余种哺乳动物化石,其中包括剑齿象和亚洲象,其地质时代为更新世晚期。杨家湾洞的剑齿象化石包括DP2, DP3, DP4, M1, M3, dp3, m2和m3等40余件;根据形态特征和测量数据,可将其归入东方剑齿象(Stegodon orientalis); 在形态方面最显著特征是乳齿的宽/长比值较大、每个齿脊上乳突数目较少和白垩质层不发育。亚洲象化石只发现2件齿板,其特征和大小均与现生亚洲象(Elephas maximus)的一致;此外, 2号洞还出土了1件门齿残段;我国南方更新世的长鼻类化石多为颊齿,门齿则报道较少;首次观察了我国化石象类门齿施氏线,其外施氏角为136°, 该数值在剑齿象和亚洲象的变化范围之内,因此,仅藉特征很难将其归入二者之一。东方剑齿象的地质分布纵贯整个更新世,但亚洲象在我国的初现时间却至今不明,其根本原因是对早–中更新世亚洲象(古菱齿象)的分类、演化问题没有很好解决;不过,在晚更新世,亚洲象已在我国南方广泛分布;依据现生亚洲象可能出现的时间判断,东方剑齿象–亚洲象组合在我国南方地区的分布时间应当是在中更新世晚期至晚更新世末期,并以晚更新世最为常见。剑齿象出现于我国南方第四纪各个时期,早更新世甚至在北方少数地点发现;真象类在早更新世期间在南方地区缺失,而中–晚更新世时却几乎遍布全国(高山地区除外)。这种时空分布上的变化,究竟是长鼻类自身演化的结果还是由环境变化所致,目前还不清楚。

Late Pleistocene proboscideans from Yangjiawan caves in Pingxiang of Jiangxi: with discussions on the Stegodon orientalis–Elephas maximus assemblage

  TONG Hao-Wen, DENG Li, CHEN Xi, ZHANG Bei ,WEN Jun

Abstract   The mammalian fauna from the Yangjiawan Caves in Jiangxi contains more than 40 species, including Stegodon and Elephas, whose age is Late Pleistocene. The 40 pieces of Stegodon fossils include such elements as DP2, DP3, DP4, M1, M3, dp3, m2 and m3, which can be included in the species S. orientalis according to their morphological characters and their dimensions; but with the following specialities: the teeth are relatively small, with thin but wrinkled enamel layer, the mammillae are lesser in number but well defined and equally developed, DP3 and dp3 with larger W/L ratios, and the cement is not well developed. The fossils of Elephas are few, only 2 isolated lamellae whose thickness and size correspond with those of Elephas maximus. In addition, a fragment of tusk (upper incisor) of elephant was also recovered, whose Schreger outer angle is 136°, which falls within the ranges of both Stegodon and Elephas. Therefore, it is difficult to refer it to either Stegodon or Elephas. This is the first sample of fossil elephant tusk with Schreger outer angle examined in China. The range of S. orientalis covered almost all of the period of Pleistocene in southern China, but the situation for E. maximus is far from clear because of the taxonomic uncertainty of the Early-Middle Pleistocene Elephas (Palaeoloxodon). It is sure that E. maximus became popular since Late Pleistocene. According to the study on the origin of the modern species of Asian elephant, the Stegodon-Elephas assemblage in southern China probably has a late Middle-Late Pleistocene age, and definitely with a Late Pleistocene age. The fossils of Stegodon were recovered throughout all the period of Quaternary in southern China, and even appeared in some localities in northern China during the Early Pleistocene. Whereas the elephantid species, including Palaeoloxodon and Elephas, were absent in southern China during the Early Pleistocene epoche, but widely spreaded during the Middle-Late Pleistocene. What should be emphasized is that it is Stegodon which used to dominate the proboscidean fauna during the whole period of Pleistocene in southern China, but the last survivor is Elephas even though it was poorly documented in the fossil records, and Stegodon got extinct around the Pleistocene/Holocene boundary.  
Key words   Yangjiawan Caves in Pingxiang, Jiangxi; Late Pleistocene; Stegodon orientalis, Elephas maximus


Late Pleistocene proboscideans from Yangjiawan caves in Pingxiang of Jiangxi: with discussions on the Stegodon orientalis–Elephas maximus assemblage
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