Cretaceous Vertebrates from Madagascar: A Window into the Biogeographic and Plate Tectonic History of Gondwana

来自马达加斯加的白垩纪脊椎动物：冈瓦纳大陆生物地理学和板块构造史的一扇窗。本研究由沉积地质与古生物学项目（EAR/GEO）和国际科学与工程办公室（OD）非洲、近东和南亚项目联合资助。【摘要】【非技术解释】中生代后半期见证了构成南部冈瓦纳超大陆的陆块结构的深刻变化，对相关的脊椎动物动物群产生了巨大影响。马达加斯加位于冈瓦纳火山的中心附近，当时它分裂成几个组成部分。该提案旨在继续一个项目，该项目旨在发现和描述岛上白垩纪地层序列中的脊椎动物化石，分析它们的古生物学，将它们置于系统发育和地质背景中，并将它们用于测试与冈瓦纳群岛（特别是马达加斯加）有关的生物地理学和板块构造假说。pi在马达加斯加白垩纪的工作才刚刚开始发挥其潜力。到目前为止，他们已经发现了岛上晚白垩纪脊椎动物的物种多样性是以前已知的五倍，并发现了一些最完整、保存最完好的南半球，甚至是世界上的晚白垩纪脊椎动物标本。许多新的分类群已被命名和描述。但在马达加斯加的白垩纪岩石中，从古生物学和地质学的角度来看，还有很多工作要做。许多分类群仅以残缺的遗迹为人所知；还有许多其他的还有待发现。随着工作的继续，pi相信马达加斯加的白垩纪脊椎动物群将成为南半球最知名和最具背景的动物群之一，并成为与其他白垩纪冈瓦纳动物群进行比较的主要标准之一。技术描述pis建议在马达加斯加西北部Mahajanga盆地Berivotra研究区继续收集白垩纪晚期陆生和淡水脊椎动物化石，该研究区继续生产鲜为人知的分类群和新分类群标本的精美材料。尽管他们已经发表了许多关于该盆地已知分类群的详细解剖、功能和系统发育分析，但更多的研究已经开始，并且仍有待完成（特别是关于白质和类鱼类、鳄鱼类、翼龙、蜥脚类和阿贝利龙类兽脚亚目恐龙、鸟类和其他类禽兽脚亚目恐龙以及哺乳动物）。其中一些工作将需要组织学采样，从而能够对生态系统规模进行比较分析，单个脊椎动物骨骼中元素间的组织学变化，并测试与系统发育受限的分类群的可能反应和生长历史适应相关的假设，但这些分类群表现出广泛的形态和功能特化。pi还建议继续开发Mahajanga盆地新发现的油田区域，这些地区产生了年龄大致相同但来自不同古环境背景的新分类群。最后，他们提议将研究范围扩大到马达加斯加西部的莫伦达瓦盆地。2010年和2012年，他们在那里进行了短暂的考察，获得了重要的发现，并证明了在比马哈扬加盆地更古老的地层中发现更多化石的潜力。这些早期的发现将为解决生物地理学和板块构造假说提供更深层次的时间背景。事实上，pi的发现继续对现存和灭绝的马达加斯加动物群的生物地理历史，以及冈瓦纳碎裂期间分散和变异的相对重要性产生深远的影响。他们的首要目标之一是在严格的系统发育框架和精确的古地理重建的背景下，为重建冈瓦纳生物地理历史提供一个关键的构建块，以时间控制的形式，从马达加斯加白垩纪采集了大量脊椎动物动物群。为了提供时间控制以及古环境和古气候背景，对所有采样层进行详细的地层学、沉积学和地层学研究仍然是一个优先事项。更具体地说，pi建议进行：(1)对Maevarano组地层学进行全面分析，为每个主要采石场提供分类摘要和地图，并详细说明Maevarano组的保存情况。特别保存的脊椎动物记录；(2)关于Maevarano组Masorobe和Anembalemba段保存完好的古土壤和相关河流沉积物的地球化学和微观形态的综合报告，这将为研究古气候提供重要的见解；(3)研究Maevarano组发现的微量化石，特别是与埋葬尸体（地下食腐）相关的回填洞穴；(4) Morondava盆地上白垩统地层的厘清和正式化研究。

Cretaceous Vertebrates from Madagascar: A Window into the Biogeographic and Plate Tectonic History of GondwanaDavid Krause, Stoneybrook, EAR-1528273Patrick O'Conner, Ohio University, EAR-1525915This proposal is jointly funded by the Sedimentary Geology and Paleobiology Program (EAR/GEO) and the Africa, Near East & South Asia Program/Office of International Science and Engineering (OD). ABSTRACTNon-technical ExplanationThe latter half of the Mesozoic Era witnessed profound changes in the configuration of landmasses that comprised the southern supercontinent Gondwana, with dramatic consequences for the associated vertebrate faunas. Madagascar lay near the center of Gondwana as it fragmented into its component parts. This proposal seeks to continue a project designed to discover and describe vertebrate fossils in a sequence of Cretaceous strata on the island, to analyze their paleobiology, to place them in phylogenetic and geologic context, and to employ them in testing biogeographic and plate tectonic hypotheses related to Gondwana as a whole and Madagascar in particular. PIs work in the Cretaceous of Madagascar is only at the very beginning of reaching its potential. To date, they have quintupled the previously known species diversity of Late Cretaceous vertebrates from the island and have discovered some of the most complete and spectacularly preserved specimens of Late Cretaceous vertebrates from the southern hemisphere and, indeed, the world. Many new taxa have been named and described. But much remains to be done in the vast expanses of paleontologically and geologically unexplored Cretaceous rocks of Madagascar. Many taxa are known by only fragmentary remains; many others are still to be discovered. With continued work, PIs are confident that Madagascar's Cretaceous vertebrate fauna will become one of the best known and best contextualized from the southern hemisphere and one of the primary standards against which other Gondwanan faunas of Cretaceous age are compared.Technical DescriptionPIs propose to continue collecting terrestrial and freshwater vertebrate fossils of latest Cretaceous age from the Berivotra Study Area of the Mahajanga Basin of northwestern Madagascar, which continues to produce exquisite material of poorly known taxa and specimens of new taxa. Although they have published many detailed anatomical, functional, and phylogenetic analyses of taxa known from this basin, many more have been initiated and remain to be completed (in particular, on albuloid and amiid fishes, crocodyliforms, pterosaurs, sauropod and abelisauroid theropod dinosaurs, birds and other paravian theropods, and mammals). Some of this work will entail histological sampling, thus enabling a comparative analysis of ecosystem-scale, inter-element histological variation within single vertebrate skeletons and testing of hypotheses related to possible responses and growth history adaptations of taxa that are phylogenetically constrained, but which exhibit a wide array of morphological and functional specializations. PIs also propose to continue developing newly discovered field areas in the Mahajanga Basin, which are yielding new taxa of roughly the same age but from different paleoenvironmental settings. Finally, they propose to expand their efforts into the Morondava Basin of western Madagascar, where brief expeditions in 2010 and 2012 yielded important finds and demonstrated the potential for many more from strata older than those yielding fossils in the Mahajanga Basin. Discoveries from these earlier horizons will provide a deeper temporal context with which to address biogeographic and plate tectonic hypotheses. Indeed, PIs discoveries continue to have profound implications for the biogeographic history of the extant and extinct Malagasy fauna and for the relative importance of dispersal and vicariance during Gondwanan fragmentation. One of their overarching goals is to provide a key building block for reconstructing Gondwanan biogeographic history in the form of a temporally controlled, well-sampled vertebrate fauna from the Cretaceous of Madagascar analyzed in a rigorous phylogenetic framework, and within the context of accurate paleogeographic reconstructions. It remains a priority to conduct detailed stratigraphic, sedimentologic, and taphonomic studies of all sampled horizons in order to provide temporal control as well as paleoenvironmental and paleoclimatic context. More specifically, PIs propose to conduct: (1) a comprehensive analysis of Maevarano Formation taphonomy that will provide taxonomic summaries and maps for each major quarry, and will detail the preservation of the Maevarano Formation?s exceptionally-preserved vertebrate record; (2) a comprehensive report on the geochemistry and micromorphology of exceptionally-preserved paleosols and associated fluvial sediments in the Masorobe and Anembalemba members of the Maevarano Formation, which will provide critical insights into paleoclimate; (3) a study focused on trace fossils discovered in the Maevarano Formation, specifically back-filled burrows associated with an entombed carcass (subterranean scavenging); and (4) a study clarifying and formalizing the lithostratigraphy of Upper Cretaceous horizons in the Morondava Basin.