COLLABORATIVE RESEARCH - Mesozoic Therians from Central Asia: the Basal radiation of Tribosphenic Mammals and their Impact on the higher-level relationships of Therian Mammals

合作研究-来自中亚的中生代兽化石：tribosphenic哺乳动物的基础辐射及其对兽目哺乳动物高级关系的影响美国自然历史博物馆的Novacek博士，路易斯维尔大学的Rougier博士，和卡内基自然历史博物馆的Wible博士，对白垩纪（1.45亿至6500万年前）哺乳动物的辐射进行了全面的研究。Therians包括活着的有袋动物和胎盘动物以及它们灭绝的亲戚。今天，兽目动物有超过4600种，几乎涵盖了所有现存哺乳动物的多样性，只有三种产卵单孔目动物除外。对兽亚目动物之间进化关系的研究已经用来自分子生物学（DNA结构）和比较解剖学（现存和灭绝形式的结构）的数据进行了处理。从这两种方法得出的家谱（系谱）并不完全一致，也不表明现生兽神的主要谱系的起源时间相同。然而，分子学和解剖学工作者都同意食虫动物样的形式是兽形类辐射的基础。Novacek，Rougier和Wible博士作为他们项目的核心研究小组，拥有保存完好的8000万年前的食虫类化石，其中一些与胎盘动物有关，另一些与有袋动物有关，这些化石是由美国博物馆和蒙古科学院最近的联合探险队从蒙古戈壁沙漠着名的恐龙和哺乳动物化石床中收集的。与绝大多数白垩纪兽化石不同，它们只是孤立的颌骨和牙齿，这些是几乎完整的骨骼。他们将提供迄今为止最全面的解剖学数据库，用于研究白垩纪兽化石和他们的后代之间的进化关系，并评估DNA和解剖结果之间有争议的差异。大多数待研究的白垩纪兽化石都是鼩 鼱大小的，因此不能仅用肉眼进行有效的研究。这些小的形式的解剖学研究需要两种工具：标准的立体显微镜和高分辨率计算机断层成像（CT扫描）。 两者都是可用的，后者在宾夕法尼亚州立大学的国家科学基金会支持的设施。诺瓦切克，鲁吉尔和Wible将利用他们在活的和灭绝的哺乳动物解剖学方面的专业知识，以及美国博物馆，卡内基博物馆和其他机构的收藏，建立一个比较信息的解剖数据库。 将通过各种现有的计算机程序从这个数据库生成家谱，并与以前根据其他信息发表的家谱进行比较。这些精美的蒙古化石是一种独特的资源，最终将被送回其原产国。仔细研究和广泛记录这些化石现在是至关重要的，以便使它们广泛用于科学进步。 这项研究的副产品将是一个标准化的兽亚目骨骼解剖学术语;目前，研究特定兽亚目谱系的研究人员使用不同的术语，这些术语往往是不一致的。 这项研究还提供了机会，教育和培训新的科学家在前和博士后水平。最后，这些化石中蕴含的宝贵科学知识将通过美国博物馆和卡内基博物馆的展览和教育项目翻译给公众。

Collaborative Research - Mesozoic therians from Central Asia: the basal radiation of tribosphenic mammals and their impact on the higher-level relationships of therian mammals A grant has been awarded to Dr. Novacek at the American Museum of Natural History, Dr. Rougier at the University of Louisville, and Dr. Wible at the Carnegie Museum of Natural History for a comprehensive study of the Cretaceous (145 to 65 million-years-ago) radiation of therian mammals. Therians include living marsupials and placentals plus their extinct relatives. Therians are represented today by more than 4600 species accounting for nearly all the diversity of living mammals, the exception being the three species of egg-laying monotremes. The study of the evolutionary relationships among therians has been addressed with data from molecular biology (the structure of DNA) and comparative anatomy (the structure of living and extinct forms). The family trees (phylogenies) that result from these two approaches are not entirely congruent nor do they suggest the same time of origin of the major lineages of living therians. However, both molecular and anatomical workers agree that insectivore-like forms are at the base of the therian radiation. Available to Drs. Novacek, Rougier, and Wible as the core study group for their project are exquisitely preserved, 80 million-year-old insectivore-like fossils, some related to placentals and others to marsupials, collected from the famed dinosaur and fossil mammal beds of Mongolia's Gobi Desert by recent joint expeditions from the American Museum and the Mongolian Academy of Sciences. Unlike the vast majority of Cretaceous therian fossils, which are merely isolated jaws and teeth, these are nearly complete skeletons. They will provide the most comprehensive anatomical data base to date for studying the evolutionary relationships among Cretaceous therians and their living descendants, and evaluating the controversial difference between DNA and anatomical results. Most of the Cretaceous therians to be studied are shrew-sized and, therefore, cannot effectively be investigated with the naked eye alone. Two tools are needed for the anatomical study of these small forms: standard stereoscopic microscopy and high-resolution computer tomographic imaging (CT-scanning). Both are available, the latter at a National Science Foundation supported facility at Pennsylvania State University. Drs. Novacek, Rougier, and Wible will use their expertise in the anatomy of living and extinct mammals, and the collections at the American Museum, Carnegie Museum, and other institutions to build an anatomical data base of comparative information. Family trees will be generated from this data base by various available computer programs and compared with those previously published based on other information. These exquisite Mongolian fossils are a unique resource that ultimately will be returned to their country of origin. Careful study and extensive documentation of these fossils now is critical in order to make them widely accessible for scientific advancement. A by-product of this study will be a standardized anatomical terminology for the therian skeleton; currently, researchers studying particular therian lineages employ different terms that are often incongruent. This study also affords the opportunity for educating and training of new scientists at both the pre- and postdoctoral level. Finally, the valuable scientific knowledge contained in these fossils will be translated for the public through the exhibits and educational programs of the American Museum and Carnegie Museum.