新疆和布克赛尔地区中泥盆世前裸子植物纲无脉树目的研究

The Class Progymnospermopsida has not only the pteridophytic free-sporing reproduction, but also the gymnospermous anatomy. The Order Aneurophytales in this class, with its great evolutionary significance, is a prime candidate for the ancestor of the gymnosperms. The aneurophytaleans emerge in large amounts worldwide in the Mid Devonian, which is an important period for the progymnosperms to evolve and diversify. However, the study on the aneurophytaleans is not thorough and still scarce, particularly in China. The Middle Devonian outcrops are well exposed in Hobuksar, North Xinjiang. The beds there produce large numbers of well-preserved aneurophytalean fossils, which are recognized as two genera (Aneurophyton and Tetraxylopteris) in the preliminary study. This program is focused on these and potential aneurophytalean fossils in Hobuksar, along with the observation of the findings in Wuppertal, Germany, to describe the morphology of Aneurophyton and Tetraxylopteris plants and the transitional specimens showing the characters of different genera, to summarize the diversity and diagnostic features of the Aneurophytales, to discuss the evolutionary path of the genera within the order and between the orders in the Progymnospermopsida, and to redraw the aneurophytalean paleophytogeographical distribution.

前裸子植物纲具有裸子植物的解剖结构却营孢子繁殖，其中的无脉树目是裸子植物祖先的有力候选者,在演化生物学上具有重要意义。中泥盆世是前裸子植物演化与分异的重要时期，无脉树目在该时段涌现于世界各地，但其研究仍欠深入且来自我国的可信报道很少。新疆和布克赛尔地区中泥盆世地层出露良好，最近产出了大量保存精美的无脉树目化石，经初步识别，至少包括两个属，适合开展形态学探讨。同时，申请人与德国无脉树目研究者交流频繁，获准研究德国相关化石。基于以上条件，本申请项目拟对新疆和布克赛尔地区的无脉树目化石展开研究，重点描述Aneurophyton和Tetraxylopteris两属植物，关注同时具有不同属特征的过渡性标本，结合世界无脉树目进展，全面总结该目植物的多样性和属种鉴别特征，讨论各属之间以及该目与其他目间的演化关系，重建无脉树目的古植物地理学分布。

新疆和布克赛尔地区中泥盆世地层出露良好，产出了大量保存精美的前裸子植物纲无脉树目化石，经与德国Wuppertal、美国纽约州及委内瑞拉的标本进行植物大形态和原位孢子对比，识别出两个本地特有种，分别属于Aneurophyton和Tetraxylopteris两属。中国的Aneurophyton生殖枝系和生殖器官形态不如德国种规律，变化较大，很可能显示了其原始性。Tetraxylopteris属的三个物虽然形态复杂（尤其是生殖器官尺寸大、结构复杂），但其总体形态和相关孢子特征在世界范围内却具有稳定性，是世界广布类群，有潜在的地层意义。无脉树目是裸子植物祖先的有力候选者。我国的无脉树目化石为全球无脉树目演化研究补充了新资料，说明泥盆纪维管植物辐射很可能起源于北冈瓦纳地区，而中、晚泥盆世今西准噶尔所属地区起到了跳板的作用。