中文摘要：

木化石是一种特殊保存形式的植物茎干化石,通常保存了精美的内部解剖结构,对研究地质历史时期植物演化和古生态学具有重要意义。尽管已经报道了中国各个地质时期的木化石200余种,但侏罗纪木化石研究相对较少,而目前还没有云南侏罗纪木化石的正式描述。本文首次报道云南中生代木化石异木（Xenoxylonsp.）。标本采自会泽县邱家大坪子中侏罗统沙溪庙组下段上部,仅保存密木型次生木质部。管胞径向壁具缘纹孔扁圆形、紧挤、单列。交叉场具1个窗格型单纹孔。生长轮明显,晚材比例很小,表明当时的降雨量充沛,并为具有一定的季节性变化的热带或亚热带的气候条件。

英文摘要：

Fossil woods are petrified/permineralised tree trunks,and commonly preserved with detailed cell structures.They are important to understand the evolutionary history of wood anatomy and palaeoecology during the deep geological past.More than200 fossil wood species have been documented in China,however,except for a few records of the Palaeozoic and Cenozoic specimens,fossil wood has not been reported from the Mesozoic deposits of Yunnan Province.Here we describe,for the first time,a Mesozoic fossil wood,Xenoxylonsp.from Yunnan Province.The materials were obtained from the Middle Jurassic Shaximiao Formation,and represent the fragments of the secondary xylem.The wood consists of thick-walled tracheids and thin-walled rays.Uniseriate bordered pits are compressed and continuously present on the radial walls of tracheids.Each cross-field has one large,simple,window-like pit.The remarkable growth rings and narrow latewood indicate that the tree inhabited in a subtropical/tropical seasonal climate,with abundant rainfall.