Shackleton Glacier Area: Evolution of Vegetation during the Triassic

该奖项由极地计划办公室南极地质和地球物理计划提供，支持对横贯北极山脉中部的三叠纪植物化石的研究。在过去的30年里，横贯北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过矿化的泥炭，生长位置硅化的化石森林，角质保存的挤压植物群，以及有趣的天狼星群化石，以及大陆上的第一只侏罗纪恐龙，仅举几例。遗址罕见的并置，包括许多不同类型的植物保存，植物化石的非凡质量，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-中生代转换是植物演化的关键时期。种子植物种类繁多，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，花卉也发生了巨大的变化。冈瓦那的二叠纪以舌翅目种子蕨类(叶型=舌蕨属)为主，但这些植物在边界上消失了，取而代之的是一直存在于整个三叠纪的被子植物种子蕨类(叶型=双子蕨类)。尽管中子植物是冈瓦那三叠纪的优势植物类群，但我们目前对它们的生物学和进化知之甚少。最近增加了我们对孢子植物系统发育的了解，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挤压化石。虽然大多数植物化石以脱节的叶、茎和生殖器官的形式出现，但沙克尔顿冰川地区的许多植物是部分连接的，因此有可能将植物部分的多样性联系起来，并更准确地了解整个植物及其在生态系统中的位置。该项目将集中于沙克尔顿冰川地区三叠纪植物群的收集和研究。将在2003-2004年实地考察期间，使用通过直升机双水獭建立的两个偏远营地进行实地工作。将收集的遗址包括柯林森山脊和施罗德山东南的一个未命名的山脊。后者已经产生了已知的唯一例子，即双微孢子叶有机地附着在带有Umkomasia生殖器官的中轴上，这使得人们能够更好地了解这些神秘的种子植物的系统发育地位，特别是与开花植物的关系。除了挤压化石外，该遗址还包括一些过矿化的泥炭和原地化石树桩。柯林森山脊遗址很重要，因为它包含了泥炭化石和可能存在于下三叠世岩石中的原木。这一年龄段的巨型植物目前在非洲大陆尚不为人所知，尽管孢粉已经被发现，根的痕迹也相对常见。然而，对1995-1996年野外采集的石化物质的初步分析表明，在这块泥炭中有大量的Glossopteris叶子，这表明可能是晚二叠世而不是早三叠世。因此，目前所知的化石植物群与基于脊椎动物化石的时代是不一致的。阐明这一地区的生物地层学是很重要的，因为二叠系-三叠系界线的位置对于了解该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实验室中对化石材料的分析将解决这些差异，并产生关于三叠纪植物进化的重要新信息。古植物学非常适合教育和推广活动。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方案，举办了关于南极科学的讲习班和临时展品，这项活动将在该项目下继续开展。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.