Late Cretaceous Vertebrates from Madagascar: Implications for Gondwanan Biogeography

马达加斯加白垩纪脊椎动物：对冈德瓦南生物地质图的影响大卫·W·克劳斯，格雷戈里·A·巴克利，凯瑟琳·A·福斯特，雷蒙德·R·罗杰斯和斯科特·D·桑普森EAR-0106477Pis先前由美国国家科学基金会资助的研究已经确定，马达加斯加西北部的Mahajanga盆地拥有南半球白垩纪晚期脊椎动物标本中一些最完整和保存最完好的标本。他们的发现使岛上已知的晚白垩世脊椎动物的物种多样性增加了五倍，现在包括鱼、青蛙、海龟、蛇、鳄鱼、恐龙、鸟类和哺乳动物的标本。更广泛地说，参与Mahajanga盆地项目的调查人员阐明了几个脊椎动物高等类群的解剖学、古生物学和系统发育关系，记录了盆地的上白垩世地层和沉积学，为岛上已灭绝和现存的脊椎动物群的生物地理起源提供了关键见解，并对中生代冈德瓦南板块构造提供了重要的新线索。然而，在Mahajanga盆地广袤的古生物学和地质学上尚未勘探的白垩纪岩石中，仍有许多工作要做。显然，即使在主要的研究区域，与世界其他地方更深入研究的区域相比，脊椎动物的多样性仍然没有得到充分的采样。此外，尽管某些分类群的标本具有精致的质量和完整性，但绝大多数物种仅由零碎和孤立的标本表示。最后，上白垩统地层的松散性质和高年降雨量确保了新地点和新标本的供应每年都会得到补充。随着持续的工作，PIS相信Mahajanga盆地脊椎动物群将成为白垩纪最好的采样动物群之一，并成为比较其他冈德瓦群岛动物群的主要标准之一。本提案的主要目标是通过以下方式扩大初步工作：在仍欠采样的主要野外地区发现更多脊椎动物化石；调查1999年发现的新野外地区；对已发现但仍未研究或仅部分研究的标本进行解剖、功能和系统发育分析；进一步阐明地质背景，包括古环境和古气候；测试与冈瓦那冰川解体有关的生物地理和板块构造假说。

ABSTRACTLATE CRETACEOUS VERTEBRATES FROM MADAGASCAR:IMPLICATIONS FOR GONDWANAN BIOGEOGRAPHYDavid W. Krause, Gregory A. Buckley, Catherine A. Forster, Raymond R. Rogers, and Scott D. SampsonEAR-0106477PIs previous NSF-funded research has established the Mahajanga Basin of NW Madagascar as having some of the most complete and spectacularly preserved specimens of Late Cretaceous vertebrates from the southern hemisphere. Their discoveries have quintupled the previously known species diversity of Late Cretaceous vertebrates from the island and now include specimens of fishes, frogs, turtles, snakes, crocodyliforms, dinosaurs, birds, and mammals. More broadly, investigators involved in the Mahajanga Basin Project have elucidated the anatomy, paleobiology, and phylogenetic relationships of several vertebrate higher taxa, documented the Upper Cretaceous stratigraphy and sedimentology of the basin, provided key insights into the biogeographic origins of both the extinct and extant vertebrate faunas of the island, and shed significant new light on Gondwanan plate tectonics during the Mesozoic. Much remains to be done, however, in the vast expanses of paleontologically and geologically unexplored Cretaceous rocks of the Mahajanga Basin. It is clear that, even in the primary study area, the diversity of vertebrates remains inadequately sampled when compared to more thoroughly studied areas elsewhere in the world. Furthermore, despite the exquisite quality and completeness of the specimens of some taxa, the vast majority of species are represented by only fragmentary and isolated specimens. Finally, the unconsolidated nature of the Upper Cretaceous strata and the high annual rainfall ensures that the supply of new localities and new specimens is replenished on an annual basis. With continued work, the PIs are confident that the Mahajanga Basin vertebrate fauna will become one of the best sampled faunas of Cretaceous age and one of the primary standards against which other Gondwanan faunas are compared. The primary goals of the current proposal are to expand preliminary efforts through additional discoveries of fossil vertebrates in the still under-sampled primary field area; investigation of new field areas discovered in 1999; anatomical, functional, and phylogenetic analysis of specimens already discovered but still unstudied or only partly studied; additional elucidation of geologic context, including paleoenvironment and paleoclimate; and testing of biogeographic and plate tectonic hypotheses related to the breakup of Gondwana.