中文摘要：

在云南省腾冲县上新统芒棒组发现了保存较好的被子植物化石密脉鹅耳枥Carpinusmio，fangiana Hu et Chaney。该种化石曾在我国山东山旺组有过报道，当前化石在叶形及叶脉特征上都和山旺的标本非常相似。进一步分析了化石叶片的角质层微细构造特征，并结合叶结构分析提高了对化石植物分类鉴定的准确性。基于化石Carpinus miofangiana与现生植物Carpinus fangiana在生态环境及其结构特征上的相似性，将Carpinus fangiana作为化石的现生对应种进行对比，并统计二者的气孔密度和气孔指数，用气孔比率的方法推测上新世的大气CO2浓度为464×10^-6，基本上与Berner全球碳平衡模型GEOCARBⅢ中CO2浓度变化曲线上的数值一致，说明C．miofangiana叶片可以作为古大气CO2浓度变化的生物指标。最后通过化石和现生叶片角质层的对比分析推断滇西地区上新世时气候比现在温暖湿润。

英文摘要：

A fossil leaf identified as Carpinus miofangiana Hu et Chaney was discovered in the Late Pliocene sediments of the Mangbang Formation, Tengchong County, Yunnan Province, China. It was well preserved with gross morphological structure and microstmcture of cuticles in situ. The gross morphological characteristics of it were similar to that of the fossil species Carpinus miofangiana from the Shanwang Formation in Shandong Province： Both of them are oblong-ovate, base obliquely cordate, leaf margin doubly minutely serrate. Their primary veins are straight and moderately thick, and the secondary veins are pinnate. Additionally, the anatomical characteristics of the present specimen are investigated here and compared with the modem leaf Carpinus fangiana. It is more credible to decide the taxonomic position of fossil plant using leaf architecture and cuticular characteristics together. As both the fossil and modem species shared similar ecological habits and clearly possessed very similar gross morphological characteristics and epidermic features, Carpinus fangiana was selected to be the fossil species nearest living equivalent species for comparative study in stomatal index. Consequently, the palaeo-atmospheric CO2 concentration, 464 ppmv, was estimated based on stomatal ratio approach. The result was consistent with the CO2 value of Bemer＇s global carbon budget model （ GEOCARB m ）. it therefore suggested that the leaf of Carpinus miofangiana can be a good proxy for palaeo-CO2 levels. Based on the comparing in cuticular characteristics between the fossil and the modem leaves, it can be inferred that the climate was warmer and more humid in the Pliocene of westem Yunnan than that of the present.