摘要：记述了新疆准噶尔盆地北缘中中新世哈拉玛盖组的两种阿特拉旱松鼠化石：Atlantoxerus junggarensis和A. xiyuensis sp. nov.依据新的化石材料将A. junggarensis特征进行了修订。新种A. xiyuensis颊齿较小，齿冠低；P4大于或等于M1/2; 次尖明显，原小尖弱小或无，后小尖强大、明显大于后尖且一般不与后边脊相连，通常无中附尖；m3无下前边尖和前齿带，无下中尖、下中附尖和下次小尖，下后脊粗壮、由下原尖伸向跟凹、不与下后尖相连，下内尖及下内脊发育。Atlantoxerus属最早的化石记录出现在中亚地区，推测它很可能起源于中亚，然后向西亚、欧洲和北非地区扩散。依据伴生动物群和相关古植物的研究成果推测，Atlantoxerus属可能生活在温暖湿润的环境中。随着晚新生代全球气温变冷，该属的分布渐趋收缩，分异度减小，表明了其地理分布与温度变化密切相关。同时推测，温度对其生存的影响似乎比湿度更大。
ATLANTOXERUS FROM THE MIDDLE MIOCENE OF NORTHERN JUNGGAR BASIN AND THEIR ENVIRONMENTAL SIGNIFICANCE
Abstract New materials of Atlantoxerus from the Middle Miocene Halamagai Formation, northern Junggar Basin, Xinjiang, are described and studied in detail. They are assigned to two species, Atlantoxerus junggarensis Wu, 1988 and A. xiyuensis sp. nov. By studying the new specimens and old materials, diagnosis of A. junggarensis is amended as: larger size, unilateral hypsodont cheek teeth, P4 larger than M1 and M2, protoconule very weak or absent, metaconule significantly larger than metacone, mesostyle and mesostylid usually present, no mesoconid, metalophid ending before metaconid, ectolophid and entolophid developed. The new species, Atlantoxerus xiyuensis, is characterized by small size, low crowned cheek teeth, P4 being larger or equal to M1/2 in size, well-developed hypocone, weak or absent protoconule, metaconule being larger than metacone and isolated from posteroloph, usually no mesostyle; m3 without anterior cingulum, anteroconid, mesoconid, mesostylid and hypoconulid, strong metalophid extending from protoconid to the talonid basin, metalophid not connected to metaconid, and well-developed entoconid and entolophid.
Referring to their associated mammals and relevant palynological records, Atlantoxerus likely lived in warm and humid environments. However, temperature is supposed to control the distribution and evolution of Atlantoxerus more significantly than humidity. Distribution of Atlantoxerus seems to be strongly affected by global climate changes. Under the influence of the Late Cenozoic global cooling, the distribution and species diversity reduced significantly.
Key words northern Junggar Basin, Middle Miocene, Atlantoxerus, climatic changes