江西萍乡杨家湾2号洞哺乳动物化石及其时代探讨

2015年11月和2016年10月先后对杨家湾2号洞化石点进行发掘。目前已出土哺乳动物化石1000多件，主要为单个牙齿化石，骨骼较少且较为破碎。初步鉴定出31个哺乳动物属种，其中偶蹄类数量最为丰富，野猪所占比例最大；灵长类和食肉类较为丰富；啮齿类、长鼻类及奇蹄类较少；尚未发现食虫类和翼手类。大部分属种为现生类群，少量灭绝属种如巴氏大熊猫、东方剑齿象及华南巨貘等。从动物群组成来看，该动物群与杨家湾1号洞、湖南道县福岩洞等动物群较为相似，属于我国南方典型的晚更新世大熊猫-剑齿象动物群，但是其所包含的动物属种相对后两个化石点都较少，尤其是小哺乳动物属种单调。杨家湾2号洞的堆积物颗粒比1号洞的较粗，且含较多角砾，缺少红色粘土；据初步判断，该洞的堆积物是由洞口进入。动物群组合指示该地区晚更新世气候较为温暖湿润。

Mammalian fossils from Yangjiawan Cave 2 of Pingxiang,Jiangxi Province and their age estimation

Yangjiawan Cave 2 fossil site (27°46'25"N, 113°50'25"E) is located in Tangshang Village of Shangli County, Pingxiang, Jiangxi Province. It is a karstic cave developed in Changxing Formation of Permian limestone and at an altitude of 241m a.s.l. It has been excavated twice during 2015~2016. The sediments of Yangjiawan Cave 2 are different from Yangjiawan Cave 1, as the former bears more breccias and lacks red clay. More than a thousand mammalian fossils have been unearthed from Yangjiawan Cave 2, which can be referred to 31 species (including indeterminate species). Most of the fossils are teeth and a few are broken bones. Sus scrofa holds the largest share of mammalian fossils. Primates and carnivores are also rich. Rodents and perissodactylas are rare. Proboscideans include Stegodon orientalis and Elephas maximus. Insectivores and chiropterans are absent. There are some extinct species, such as Ailuropoda baconi, Stegodon orientalis and Megatapirus augustus. In faunal composition, Yangjiawan Cave 2 belongs to Late Pleistocene Ailuropoda-Stegodon fauna, which is similar to the Yangjiawan Cave 1 and Fuyan Cave. However, the number of species of Yangjiawan Cave 2 is less than the latter two, especially on the micromammals. In addition, the dental measurements of Ailuropoda baconi and the presence of Elephas maximus also indicate that the time of Yangjiawan Cave 2 is similar to Yangjiawan Cave 1 and Fuyan Cave. The presence of Elephas maximus, Megatapirus augustus and Cervus (Rusa)unicolor in Yangjiawan Cave 2 fauna implies that the climate in Jiangxi were warm and humid in the Late Pleistocene.