A Non-amniote Perspective on the Recovery from the End-Permian Extinction at High Latitudes: Paleobiology of Early Triassic Temnospondyls from Antarctica

大约2.52亿年前，地球上90%以上的物种灭绝。与这次灭绝同时发生的是，盘古大陆的南极部分过渡到一个没有永久冰盖的更温暖的气候状态。与低纬度地区相比，人们对南极洲灭绝幸存者的了解相对较少，尽管有人假设，大陆更极地的位置使它免受最严重的灭绝影响。作为2017/2018年美国国家科学基金会赞助的深野外营地的结果，在沙克尔顿冰川地区的岩石中发现了一批非凡的脊椎动物化石。这个收藏包括在南极洲发现的保存最好、最完整的两栖动物化石材料，包括两个以前未被描述过的物种。该基金支持一名具有两栖动物化石专业知识的博士后研究人员描述和解释这些化石的意义，包括它们的鉴定、关系，以及它们如何适应南极洲的陆地生态系统和其他南半球陆地组合，以适应灭绝后环境的重大重组。两栖动物化石的历史收藏也将作为这项工作的一部分进行审查。华盛顿大学的本科生将积极参与这项研究，并学习硬组织组织学和CT数据处理等技能。公众对南极科学的参与将在华盛顿大学伯克博物馆完成，该博物馆是华盛顿州自然历史和文化博物馆。具体来说，一个关于南极两栖动物的新展览将被开发为古生物学画廊的一部分，该画廊每年接待超过10万名游客。这个为期两年的项目将根据最近在南极洲沙克尔顿冰川地区发现的大量化石，研究三叠纪temnospondyls的进化。从Fremouw组中部收集的Temnospondyls是该地层段第一批可识别的四足动物化石的一部分。对这些化石进行彻底的解剖描述和比较将增加新的动物信息，也有助于确定这个地层的年龄是早三叠世还是中三叠世。保存完好的来自fremow地层下部的temnospondyl材料将允许比以前更精确的识别，并将提供在灭绝恢复间隔中其辐射的最早阶段的见解。总的来说，首席研究员和博士后研究员将率先努力修改南极Temnospondyli成员的系统分类，并将它们适当地置于三叠纪四足动物进化的框架中。研究小组还将利用两栖动物化石对气候敏感的特性，通过对选定的化石进行组织学分析，更好地了解中生代早期高纬度地区的季节性模式。初步数据表明，与此间隔前后的分布相比，在二叠纪末灭绝之后，temnospondyls具有异常多样化和高度地方性。如果得到证实，这种宏观进化模式可以用来预测现代两栖动物对未来气候扰动的反应。总的来说，这项研究将为Fremouw组的脊椎动物动物群提供新的见解，并揭示二叠纪-三叠纪大灭绝后盘古大陆南部陆地生态系统的演变。作为更广泛影响的一部分，研究小组将帮助开发一个展览，展示一些保存最完好的南极化石，向公众解释古生物学家如何使用化石和岩石来了解过去的气候，比如三叠纪的“温室”世界，在两极缺乏永久的冰盖。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Non-technical AbstractAround 252 million years ago, a major mass extinction wiped out over 90% of species on Earth. Coincident with this extinction, the Antarctic portion of the supercontinent of Pangea transitioned to a warmer climatic regime devoid of a permanent ice cap. Compared to lower latitudes, relatively little is known about the survivors of the extinction in Antarctica, although it has been hypothesized that the continents more polar location shielded it from the worst of the extinctions effects. As the result of a NSF-sponsored deep field camp in 2017/2018, a remarkable collection of vertebrate fossils was discovered in the rocks of the Shackleton Glacier region. This collection includes the best preserved and most complete materials of fossil amphibians ever recovered from Antarctica, including two previously undescribed species. This grant supports one postdoctoral researcher with expertise in fossil amphibians to describe and interpret the significance of these fossils, including their identification, relationships, and how they fit into the terrestrial ecosystem of Antarctica and other southern hemisphere terrestrial assemblages in light of the major reorganization of post-extinction environments. Historical collections of fossil amphibians will also be reviewed as part of this work. Undergraduate students at the University of Washington will be actively involved as part of this research and learn skills like hard tissue histology and CT data manipulation. Public engagement in Antarctic science will be accomplished at the University of Washington Burke Museum, which is the Washington State museum of natural history and culture. Specifically, a new exhibit on Antarctic amphibians will be developed as part of the paleontology gallery, which sees over 100,000 visitors per year.Technical AbstractThis two-year project will examine the evolution of Triassic temnospondyls based on a remarkable collection of fossils recently recovered from the Shackleton Glacier region of Antarctica. Temnospondyls collected from the middle member of the Fremouw Formation are part of the first collection of identifiable tetrapod fossils from this stratigraphic interval. Thorough anatomical description and comparisons of these fossils will add new faunal information and also aid in determining if this horizon is Early or Middle Triassic in age. Exquisitely preserved temnospondyl material from the lower Fremouw Formation will permit more precise identification than previously possible and will provide insights into the earliest stages of their radiation in the extinction recovery interval. Overall, the Principal Investigator and Postdoctoral Researcher will spearhead an effort to revise the systematics of the Antarctic members of Temnospondyli and properly contextualize them in the framework of Triassic tetrapod evolution. The research team will also take advantage of the climate-sensitive nature of fossil amphibians to better understand patterns of seasonality at high-latitudes during the early Mesozoic by subjecting selected fossils to histological analysis. Preliminary data suggest that temnospondyls were exceptionally diverse and highly endemic immediately after the end-Permian extinction, when compared to their distribution before and after this interval. If confirmed, this macroevolutionary pattern could be used to predict the response of modern amphibians to future climate perturbations. Overall, this research will provide new insights into the vertebrate fauna of the Fremouw Formation, as well as shed light on the evolution of terrestrial ecosystems in southern Pangea in the wake of the Permian-Triassic mass extinction. As part of the broader impacts, the research team will help to develop an exhibit featuring some of the best preserved fossils from Antarctica to explain to the public how paleontologists use fossils and rocks to understand past climates like the Triassic 'hot-house' world that lacked permanent ice caps at the poles.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.