Collaborative Research: Late Cretaceous Vertebrates from Madagascar: Implications for the Plate Tectonic and Biogeographid History of Gondwana

克劳斯9418816目前的提议的目标是大幅增加对马达加斯加晚白垩世脊椎动物的了解，目前人们对该动物群知之甚少。随着对马达加斯加西北部Mahajanga盆地更多和更完整的脊椎动物化石的发现和分析，将有可能解决与晚白垩世冈瓦那东部各组成部分的物理和生物联系以及马达加斯加现存脊椎动物的生物地理起源有关的三个关键(但不是相互排斥的)假说：假说一：马达加斯加、非洲和印度次大陆，由于物理上的邻近，在晚白垩世共享脊椎动物动物群，在某些情况下在物种水平上非常相似。许多来自马达加斯加晚白垩世的脊椎动物被认为与非洲和印度的脊椎动物密切相关，或者在某些情况下是同种的。相应地，地球物理学家普遍认为，印度次大陆此时接近或毗邻马达加斯加的东缘。尽管马达加斯加、非洲和印度的晚白垩世脊椎动物群有明显的相似之处，但由于材料不足，很难进行详细的比较。要进行这样的比较，需要来自马达加斯加(以及印度和非洲)的更完整的脊椎动物化石材料。假设二：在晚白垩世后期，印度次大陆在动物群上与马达加斯加(和非洲)隔绝，在最近的白垩纪，含有来自劳拉西斯(由于与欧亚大陆碰撞的结果)的元素，而不是与马达加斯加(或非洲)共享的元素。一些证据被用来支持最近有争议的假设，即印度次大陆在白垩纪末期已经与欧亚大陆相撞。据称在印度马斯特里赫特的老挝人群体的存在表明，到目前为止，印度次大陆和欧亚大陆之间可能已经存在一条更陆上的路线。然而，用于支持这一结论的材料由孤立的、支离破碎的、具有可疑鉴定的稀有标本组成。对来自Mahajanga盆地的一些标本的初步鉴定表明，至少有一些在印度晚白垩世发现的“Laurasian”分类群也出现在马达加斯加。如果这些确认得到证实，那么这些“劳亚”分子更有可能是通过非洲和马达加斯加进入印度次大陆的，而不是从欧亚大陆。假设III：在新生代开始之前，一些组成马达加斯加现存动物群的脊椎动物高等类群(如狐猴形目、网虫科、冬虫科)在岛上定居。马达加斯加现存的、高度地方性和不平衡的脊椎动物的生物地理起源尚不清楚，几十年来一直是推测辩论的主题。这在很大程度上是因为岛上实际上没有陆相的、前全新世的新生代地层。因此，揭示这一重大问题的最佳机会是在Mahajanga盆地富含化石的上白垩统非海相地层中发现脊椎动物化石。这个项目的大部分意义在于发现和了解更多关于晚白垩世生活在马达加斯加的脊椎动物的信息。通过拟议的两个野外季节获得的化石收集将远远超过以前的所有努力(加在一起)，并将对“Maevarano”和“Marovoay”地层中脊椎动物的多样性提供合理的估计。在积累和分析数据以验证上述假设的过程中，我们希望：1)大大有助于了解马达加斯加晚白垩世脊椎动物的多样性、解剖学和系统发育关系；以及2)更好地约束富含化石地层的岩石地层学和生物地层学(并正式确定“Marvoay”、“Maaevarano”和“Berivotra”组)。

Krause 9418816 The goal of the current proposal is to substantially increase knowledge of the Late Cretaceous vertebrate fauna of Madagascar, which is currently very poorly known. With the discovery and analysis of additional and more complete vertebrate fossils from the Mahajanga Basin of northwestern Madagascar, it will be possible to address three critical (but not mutually exclusive) hypotheses relating to the physical and biotic connections of the component parts of eastern Gondwana during the Late Cretaceous and the biogeographic origins of the extant vertebrate fauna of Madagascar: HYPOTHESIS I: Madagascar, Africa, and the Indian subcontinent, owing to their physical proximity, shared vertebrate faunas in the Late Cretaceous that were very similar, in some cases at the species level. Many of the vertebrates from the Late Cretaceous of Madagascar are thought to be closely related to or, in some cases, conspecific with those of Africa and India. Correspondingly, there is general agreement among geophysicists that the Indian subcontinent was close or adjacent to the eastern margin of Madagascar at this time. Despite apparent similarities in the Late Cretaceous vertebrate faunas of Madagascar, Africa, and India, detailed comparisons have been difficult due to inadequate material. More complete material of vertebrate fossils from Madagascar (as well as India and Africa) are needed for such comparisons to be made. HYPOTHESIS II: The Indian subcontinent was faunally isolated from Madagascar (and Africa) in the later stages of the Late Cretaceous and, in the latest Cretaceous, contained elements from Laurasis (as a result of collision with Eurasia) that were not shared with Madagascar (or Africa). Some of the evidence used in support of the recent and controversial hypothesis that the Indian subcontinent had already collided with Eurasia by the latest Cretaceous is paleontological. The presence of purportedly Laurasian groups in the Maastrichtian of India indicated that a ter restrial route between the Indian subcontinent and Eurasia may have existed by this time. However, the material used to support this conclusion consists of isolated, fragmentary, and rare specimens with questionable identifications. Preliminary identifications of some specimens form the Mahajanga Basin indicate that at least some of the "Laurasian" taxa found in the Late Cretaceous of India also occurred in Madagascar. If these identifications are confirmed, it is more likely that these "Laurasian" elements entered the Indian subcontinent by way of Africa and Madagascar, rather than from Eurasia. HYPOTHESIS III: Some vertebrate higher taxa that comprise the extant fauna of Madagascar (e.g., Lemuriformes, Tenrecidae, Cordylidae) colonized the island prior to the beginning of the Cenozoic. The biogeographic origins of the extant, highly endemic and imbalanced vertebrate fauna of Madagascar are unknown and have been the subject of speculative debate for many decades. This is largely the result of the virtual absence of nonmarine, pre-Holocene Cenozoic strata on the island. As a result, the best opportunity to shed light on this major problem is to discover vertebrate fossils in the richly fossiliferous Upper Cretaceous nonmarine strata of the Mahajanga Basin. Much of the significance of this project lies in discovering and understanding more about the vertebrates that lived in Madagascar during the Late Cretaceous. Fossil collections obtained through the proposed two field seasons will far exceed all previous efforts (combined) and will provide a reasonable estimate of the diversity of vertebrates in the "Maevarano" and "Marovoay" formations. In the process of accumulating and analyzing data to test the hypotheses above, we expect to: 1) contribute substantially to knowledge of the diversity, anatomy, and phylogenetic relationships of the Late Cretaceous vertebrates of Madagascar; and 2) better constrain the lithostratigraphy and biostratigraphy of the fossiliferous beds (and to de fine formally the "Maravoay", "Maaevarano", and "Berivotra" formations).