Shackleton Glacier Area: Evolution of Vegetation during the Triassic

该奖项由极地项目办公室的南极地质和地球物理项目提供，支持对南极中部横贯山脉三叠纪植物化石的研究。在过去的30年里，横贯南极山脉中部的陆相岩石一直是杰出化石发现的来源，包括二叠纪和三叠纪的过矿化泥炭，生长位置硅化的化石林，表皮保存的压缩植物群，以及有趣的天狼星群化石，以及来自大陆的第一只侏罗纪恐龙，仅举几例。包括许多不同类型植物保存的遗址罕见地并列在一起，植物化石的卓越品质以及遗址的生物多样性使该地区在世界上独一无二。古生代与中生代的过渡是植物进化的关键时期。存在一种独特的种子植物群，其中一些被认为是被子植物（开花植物）的祖先。从二叠纪到三叠纪，植物也发生了巨大的变化。Gondwana的二叠纪以舌状种子蕨类植物（叶片类型= gloopteris）为主，但这些植物在边界处消失，被尾状种子蕨类植物（叶片类型= Dicroidium）所取代，并在整个三叠纪持续存在。虽然在冈瓦纳三叠纪时期，长尾植物是占优势的植物群，但我们目前对它们的生物学和进化知之甚少。最近，来自比尔德莫尔冰川地区的过矿化泥炭和来自沙克尔顿冰川地区保存异常完好的压缩化石，增加了我们对囊胚系统发育的了解。虽然大多数植物化石都是无节的叶、茎和生殖器官，但在沙克尔顿冰川地区的许多化石都是部分铰接的，因此有可能将植物部分的多样性联系起来，并获得整个植物及其在生态系统中的位置的更准确的图像。该项目将集中收集和研究沙克尔顿冰川地区的三叠纪植物群。野外调查将于2003-2004年进行，使用直升机Twin Otter建立的两个偏远营地。收集的地点包括科林森岭和施罗德山东南的一个未命名的山脊。后者已经产生了唯一已知的双子叶有机地附着在带有Umkomasia生殖器官的轴上的例子，这使得人们更好地了解这些神秘的种子植物的系统发育位置，特别是与开花植物的关系。除了压缩化石外，该遗址还包括一些过矿化泥炭和原位化石残桩。科林森岭的遗址很重要，因为它含有泥炭化石和可能是下三叠纪岩石中的原木。这个时代的巨型植物化石目前在非洲大陆上是未知的，尽管已经发现了异形植物，根的痕迹也相对常见。然而，对1995-1996年野外季节收集的石化材料的初步分析显示，这块泥炭中有大量的舌蕨树叶，这表明它可能是晚二叠纪而不是早三叠纪。因此，目前已知的化石植物群与基于脊椎动物化石的年龄不一致。阐明该地区的生物地层学是很重要的，因为二叠纪-三叠纪界线的位置对于了解界线周围陆地灭绝的时间至关重要。在这两个地点的进一步收集和在实验室对化石材料的分析将解决这些差异，并获得有关三叠纪植物进化的重要新信息。古植物学非常适合于教育和推广活动。通过堪萨斯大学自然历史博物馆和生物多样性研究中心的公共宣传计划，开展了关于南极科学的讲习班和临时展览，并将在本项目下继续开展这项活动。学生的参与也很广泛，并将通过本科生的研究经验继续下去。

This award, provided by the Antarctic Geology and Geophysics Program of the Office of Polar Programs, supports a study of the Triassic plant fossils from the Central Transantarctic Mountains. The terrestrial rocks of the central Transantarctic Mountains have been a source of outstanding fossil discoveries over the last 30 years, including Permian and Triassic permineralized peat, fossil forests silicified in growth position, and compression floras with cuticular preservation, as well as the interesting Sirius Group fossils, and the first Jurassic dinosaur from the continent, to name only a few. The rare juxtaposition of sites that include many different types of plant preservation, the exceptional quality of the plant fossils, and the biodiversity of the sites make this area unique in the world. The Paleozoic/Mesozoic transition is a critical time in plant evolution. A unique variety of seed plant groups existed and several of these have been suggested as angiosperm (flowering plant) ancestors. There was also a massive floral change from the Permian to the Triassic. The Permian of Gondwana is dominated by glossopterid seed ferns (leaf type = Glossopteris), but these plants disappeared at the boundary to be replaced by the corystosperm seed ferns (leaf type = Dicroidium), which persisted throughout the Triassic. Although the Corystospermales were the dominant plant group in the Triassic of Gondwana, we currently know very little about their biology and evolution. Recent additions to our knowledge of corystosperm phylogeny have come from permineralized peat from the Beardmore Glacier area and from exceptionally well-preserved compression fossils from the Shackleton Glacier area. While most fossil plants occur as disarticulates leaves, stems, and reproductive organs, many in the Shackleton Glacier area are partially articulated, thus making it possible to relate the diversity of plant parts and gain a more accurate picture of the entire plant and its place within the ecosystem. This project will center on the collection and study of Triassic floras from the Shackleton Glacier area. Fieldwork will be conducted in the 2003-2004 field season using two remote camps established via Twin Otter of helicopter. The sites to be collected include Collinson Ridge and an unnamed ridge southeast of Schroeder Hill. The latter has already yielded the only known example of a Dicroidium frond organically attached to an axis bearing Umkomasia reproductive organs, which has allowed a better understanding of the phylogenetic position of these enigmatic seed plants, especially in relationship to flowering plants. In addition to compression fossils, this site also includes some permineralized peat and in situ fossil stumps. The Collinson Ridge site is important because it contains fossil peat and logs in presumably Lower Triassic rocks. Megafossil plants of this age are currently unknown on the continent, although palynomorphs have been recovered and root traces are relatively common. Preliminary analysis of petrified material collected during the 1995-1996 field season, however, shows a large number of Glossopteris leaves in this peat, suggesting that perhaps it is Late Permian rather than Early Triassic. Thus the fossil flora, as it is currently known, is at odds with the age based on vertebrate fossils. It is important to elucidate the biostratigraphy of this area because the position of the Permian-Triassic boundary is crucial in understanding the timing of terrestrial extinctions around the boundary. Further collecting at both of these sites and analysis of the fossil material in the laboratory will address these discrepancies and yield important new information about Triassic plant evolution.Paleobotany is ideally suited to education and outreach activities. Workshops and temporary exhibits have been developed on Antarctic science through the public outreach programs of the University of Kansas Natural History Museum and Biodiversity Research Center, and this activity will be continued under this project. Student involvement has also been extensive and will be continued through research experiences for undergraduates.