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报道了一种具混合型纹孔 (互列式纹孔和对列式纹孔 )的化石木。化石木产自内蒙古乌达矿区老石旦矿附近太原组上部 ,地质时代为早二叠世早期。经比较 ,确认为南洋杉型木属 (AraucarioxylonKraus)一新种 :老石旦南洋杉型木 (Araucarioxylonlaoshidanensesp .nov .)。根据混合型纹孔的存在及其他特征 ,认为新种可能代表了一种原始的松杉类植物的木材化石。主要特征 :仅保存有次生木质部 ,无生长轮 ,仅由轴向管胞和木射线构成 ,未见轴向薄壁组织和树脂道。管胞排列紧密 ,径向壁具缘纹孔 1～ 4列 ,其中 2～ 3列者较常见。纹孔的排列以互列紧挤为主 ,也有少量对列 亚对列的纹孔。交叉场内多具 1～ 2个柏木式纹孔。木射线多为单列 ,少数为部分双列 ,高 2～ 39个(多为 3～ 5个 )细胞。
A fossil wood with mixed pits (interlaid plies and paired pits) was reported. Fossil wood is from the upper part of Taiyuan Formation near Laodeandan mine in Wuda, Inner Mongolia. The geological period was early Early Permian. A new species of Araucarioxylon Kraus was identified as Araucarioxylonlaoshidanensesp. Nov. Based on the presence of mixed pits and other features, it is believed that the new species may represent a primitive fossil of fagaceous plants. Main features: Only preserved secondary xylem, no growth wheel, only by axial tracheids and wood-ray composition, no axial parenchyma and resin road. Tracheids arranged in close, radial wall margin pits 1 to 4 columns, of which 2 to 3 are more common. Pits arranged in tight intercropping of the main, there are a small amount of the column on the column of Leah. Crosses more than 1 to 2 cedar pits. Wood rays are mostly single, a small number of partial double, high 2 to 39 (mostly 3 to 5) cells.