Non-destructive High Resolution CT-scanning of a Crocodilian-bearing Vertebrate Fossil-Lagerstatte from a 110 Ma Mid-Pacific Drowned Atoll, Ocean Drilling Program (ODP) Site 865

PIS在中太平洋山脉ODP865孔底部附近30厘米厚的泥岩中发现了一种独特的上阿普提亚/下阿尔比亚泻湖脊椎动物拉格斯坦岩化石，该孔位于太平洋中部，沉积时约110 Ma，距离所有大陆都很远。这一发现是中太平洋地区白垩纪爬行动物遗骸的唯一已知记录，也是太平洋海洋领域已知的最古老的鳄鱼遗骸。到目前为止，他们已经发现了一颗1厘米长的原始鳄鱼牙齿，其他几颗保存完好的较小的鳄鱼牙齿，代表各种摄食策略的鱼牙齿，鱼鳞，以及目前身份不明的脊椎动物骨骼。与之相关的有陆地植物碎片、孢粉、琥珀、淡水藻类遗骸、牡蛎和介形虫。丰富的黄铁矿、海绿石和环境敏感的介形类，指示了低氧条件下受限的海洋古环境。该沉积物有可能产生其他白垩纪脊椎动物的遗骸，如其他海洋爬行动物、鸟类、翼龙和陆地岛屿动物群。为了最大限度地减少对这种少量岩心材料的进一步破坏性采样，PI将使用德克萨斯大学的超高分辨率X射线CT系统来构建该岩心间隔的高分辨率3D图像。这种成像将使他们能够从岩心工作的一半定位和提取其他脊椎动物遗骸，并查看存档岩心一半中无法破坏性采样的所有脊椎动物遗骸。CT成像还将使PI能够研究沉积构造，以了解该层的沉积历史。其他近岸海洋和陆地沉积物也存在于其他深海钻探岩心中，对此沉积物进行CT扫描将证明其在寻找可能存在的脊椎动物方面的有效性。这项研究的意义在于，它将提供一个独特的、史无前例的白垩纪脊椎动物动物群的视角，生活在远离任何其他已知的白垩纪和大陆爬行动物遗骸的泻湖古环境中。这将为我们理解脊椎动物进化、古生态和古迁徙提供一个独特的视角。这项研究完成后，从这个岩心提取的脊椎动物遗骸将永久保存在德克萨斯州奥斯汀的德克萨斯自然科学中心，这里是德克萨斯纪念博物馆的所在地。CT图像将被存档在德克萨斯大学奥斯汀分校由NSF支持的数字形态图书馆。ODP型钻芯的一半永久档案将储存在德克萨斯农工大学综合海洋钻探计划的墨西哥湾沿岸储存库。

PIs have discovered a unique upper Aptian/lower Albian lagoonal vertebrate fossil lagerstatte in a 30 cm thick mudstone sandwiched between oceanic island basalt sills near the base of ODP Hole 865 in the Mid-Pacific Mountains, which, at the time of deposition about 110 Ma, was located in the middle of the Pacific Ocean about as far away from all continents as possible. This discovery represents the only known record of Cretaceous reptilian remains from the mid-Pacific region, and the oldest known crocodilian remains in the Pacific oceanic realm. So far, they have recovered a pristine 1 cm long cone of a crocodilian tooth, several other well preserved smaller crocodilian teeth, fish teeth representing a variety of feeding strategies, fish scales, and currently unidentified vertebrate bones. Associated with these are terrestrial plant debris, palynomorphs, amber, freshwater algal remains, oysters, and ostracods. Abundant pyrite, glauconite, and environmentally sensitive ostracods, indicate a restricted marine paleoenvironnment with low oxygen conditions. This deposit has the potential of yielding remains of other Cretaceous vertebrates such as other marine reptiles, birds, pterosaurs and terrestrial island fauna. To minimize further destructive sampling of this small amount of core material, PIs will use the ultra-high resolution X-ray CT system at the University of Texas to construct high-resolution 3D images of this core interval. This imaging will allow them to locate and extract other vertebrate remains from the working half of the core, and view all vertebrate remains in the archive core half which cannot be sampled destructively. CT imaging will also enable PIs to study the sedimentary structures in order to understand the depositional history of this layer. Other near-shore marine and terrestrial deposits occur in other deep-sea drill cores, and the use of CT-scanning on this deposit will demonstrate its usefulness in searching other cores for possible vertebrate remains.The significance of this research is that it will provide a unique, unprecedented view of a Cretaceous vertebrate fauna living in a lagoonal paleoenvironment as far removed as possible from any other known Cretaceous and continental reptilian remains. This will add a unique perspective to our understanding of vertebrate evolution, paleoecology and paleomigrations.After completion of this study, the vertebrate remains extracted from this core will be stored permanently at the Texas Natural Science Center, which houses the Texas Memorial Museum, in Austin, Texas. The CT images will be archived in the NSF supported Digital Morphology Library at the University of Texas at Austin. The permanent archive half of the ODP core will be stored at the Gulf Coast Repository of the Integrated Ocean Drilling Program at Texas A&M University.