Department of Environmental and Plant Biology, Ohio University, Athens, Ohio 45701 USA;
Am J Bot. 2002 Feb;89(2):352-61. doi: 10.3732/ajb.89.2.352.
Numerous small fern trunks and dispersed osmundaceous frond fragments occur within a Middle Triassic silicified peat near Fremouw Peak in the Transantarctic Mountains of Antarctica. These specimens form the basis of a new species of osmundaceous ferns that further helps to characterize the early Mesozoic vegetation of high latitude Gondwana. Ashicaulis woolfei n. sp. consists of small, upright trunks with a persistent armor of frond bases, adventitious roots, and vegetative frond parts. In cross section the trunks are ∼2.5 cm in diameter and include up to 45 frond bases. Stems range from 5 to 8 mm in diameter with a xylem cylinder of 8-9 xylem segments separated by leaf gaps. Phyllotaxy is variable, approaching 2/5 or 3/8, with 10-12 frond traces in the cortex. Stipes have parenchymatous, stipular wings that are usually devoid of sclerenchyma; fronds are pinnate with alternate-subopposite pinnatifid pinnules. Although the absence of fertile pinnules and sporangia precludes assigning the fossils to a living genus, this species demonstrates that ferns with stelar architecture and histology similar to Osmunda subgenus Osmundastrum (Osmundaceae) were present in the Southern Hemisphere by the mid-Triassic.
在南极洲的南极横贯山脉弗雷莫尔峰附近的中三叠统硅化泥炭中，发现了许多小型蕨类树干和分散的鳞毛蕨叶片碎片。这些标本是一种新的鳞毛蕨属蕨类植物的基础，进一步有助于描绘高纬度冈瓦纳早中生代的植被特征。Ashicaulis woolfei n. sp. 由小型直立的树干组成，具有持久的叶片基部、不定根和营养叶片部分的保护装甲。在横截面上，树干直径约为 2.5 厘米，包含多达 45 个叶片基部。茎干直径从 5 到 8 毫米不等，木质部圆柱体由 8-9 个木质部节组成，由叶隙隔开。叶序变化不定，接近 2/5 或 3/8，外皮层中有 10-12 个叶片痕迹。叶柄具薄壁组织、叶舌状翅，通常缺乏厚壁组织；叶片为羽状，互生或对生，有羽裂的小裂片。尽管缺乏可育的小羽片和孢子囊，无法将化石归入现生属，但该物种表明，具有类似于鳞毛蕨属 Osmundastrum 亚属（鳞毛蕨科）的茎干结构和组织学的蕨类植物在中三叠世就已经存在于南半球。
