The Mahajanga Basin Project: Late Cretaceous Vertebrates from Madagascar and Their Implications for the Biogeographic History of Gondwana

地球的面貌在晚侏罗世和白垩纪发生了翻天覆地的变化。正是在这段时间内，南部超大陆冈瓦纳分裂成孤立的大陆块，对相关的陆生和淡水脊椎动物（脊骨动物）造成了严重后果。这种碎裂的时间和顺序的重建几乎完全基于地球物理证据，并且在陆生和淡水脊椎动物化石的基础上仍然缺乏测试。本提案旨在继续和扩大一个项目，该项目旨在发现马达加斯加西北部Mahajanga盆地上白垩纪地层（大约6500万年）中的脊椎动物化石，将它们置于系统发育、地层学和沉积学背景下，并利用它们来测试与冈瓦纳大陆整体，特别是马达加斯加有关的生物地理学和板块构造假说。Mahajanga盆地项目于十多年前启动，但才刚刚开始发挥其潜力。迄今为止，科学家们已经将岛上晚白垩纪脊椎动物的物种多样性增加了五倍，并发现了一些来自南半球乃至世界上保存最完整、最壮观的晚白垩纪脊椎动物标本。但采样显然是不完整的，在Mahajanga盆地的白垩纪岩石中，还有很多工作要做，这些岩石在古生物学和地质学上都没有被探索过。随着工作的继续，pi相信Mahajanga盆地白垩纪的脊椎动物动物群将成为南半球白垩纪时代采样最多、最知名的动物群之一，并成为与其他冈瓦南白垩纪时代动物群进行比较的主要标准之一。在马达加斯加西北部Mahajanga盆地的上白垩纪地层中发现了更多更完整的脊椎动物化石，并对其进行了严格的系统发育分析，并将其置于地质环境中，将：1)揭示了冈瓦纳大陆南部超大陆（特别是马达加斯加）脊椎动物的多样性和进化历史；2)验证了关于冈瓦纳大陆各组成部分在中生代的物理和生物联系的相互矛盾的假设；并有助于阐明马达加斯加高度特有的现存脊椎动物动物群的生物地理起源，这可以说是自然史上最大的未解之谜之一。与过去一样，这个项目坚定地致力于为马达加斯加的研究生和美国的高中、本科生、研究生以及博士后提供一个培训基地。与以往一样，该项目的成果将以各种方式向科学界和公众传播，包括原创出版物、媒体曝光、互联网、博物馆展示和讲座/研讨会。pi还将继续努力，通过1998年成立的一个组织，即马达加斯加Ankizy基金（www.ankizy.org），为生活在马达加斯加偏远地区的儿童修建学校和提供医疗保健。

The face of the Earth changed radically during the Late Jurassic and Cretaceous. It is during this interval that the southern supercontinent Gondwana fragmented into isolated landmasses, with dramatic consequences for the associated terrestrial and freshwater vertebrate (backboned) animals. Reconstructions of the timing and sequence of this fragmentation are based almost entirely on geophysical evidence and remain poorly tested on the basis of terrestrial and freshwater vertebrate fossils. This proposal seeks to continue and expand a project designed to discover vertebrate fossils in Upper Cretaceous strata (approximately 65 million years old) of the Mahajanga Basin in northwestern Madagascar, to place them in phylogenetic, stratigraphic, and sedimentologic context, and to employ them in testing biogeographic and plate tectonic hypotheses relating to Gondwana as a whole and Madagascar in particular. The Mahajanga Basin Project was initiated over a decade ago but is only beginning to reach its potential. To date, PIs 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. But sampling is clearly incomplete and much remains to be done in the vast expanses of paleontologically and geologically unexplored Cretaceous rocks of the Mahajanga Basin. With continued work, PIs are confident that the vertebrate fauna from the Cretaceous of the Mahajanga Basin will become one of the best sampled and best known faunas of Cretaceous age from the southern hemisphere and one of the primary standards against which other Gondwanan faunas of Cretaceous age are compared. The discovery and rigorous phylogenetic analysis of additional and more complete vertebrate fossils from Upper Cretaceous horizons in the Mahajanga Basin of northwestern Madagascar, and their placement in geological context, will: 1) shed significant new light on the diversity and evolutionary history of vertebrates from the southern supercontinent of Gondwana in general and Madagascar in particular, and 2) permit tests of competing hypotheses about the physical and biotic connections of the component parts of Gondwana during the Mesozoic and serve to elucidate the biogeographic origins of the highly endemic extant vertebrate fauna of Madagascar, arguably one of the greatest unsolved mysteries of natural history. As in the past, this project is firmly committed to providing a training ground for both Malagasy graduate students and for American high school, undergraduate, and graduate students, as well as postdoctoral associates. Also as in the past, results of this project will be disseminated to both the scientific community and the general public in a variety of ways including original publication, media exposure, the internet, museum displays, and lectures/seminars. PIs will also continue their efforts to build schools and provide healthcare for children living in remote areas of Madagascar through an organization, the Madagascar Ankizy Fund (www.ankizy.org), that they established in 1998.