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Dietary specializations and diversity in feeding ecology of the earliest stem mammals

机译：最早干哺乳动物的饮食专长和饮食生态多样性

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摘要

The origin and radiation of mammals are key events in the history of life, with fossils placing the origin at 220 million years ago, in the Late Triassic period. The earliest mammals, representing the first 50 million years of their evolution and including the most basal taxa, are widely considered to be generalized insectivores. This implies that the first phase of the mammalian radiation-associated with the appearance in the fossil record of important innovations such as heterodont dentition, diphyodonty and the dentary-squamosal jaw joint-was decoupled from ecomorphological diversification. Finds of exceptionally complete specimens of later Mesozoic mammals have revealed greater ecomorphological diversity than previously suspected, including adaptations for swimming, burrowing, digging and even gliding, but such well-preserved fossils of earlier mammals do not exist, and robust analysis of their ecomorphological diversity has previously been lacking. Here we present the results of an integrated analysis, using synchrotron X-ray tomography and analyses of biomechanics, finite element models and tooth microwear textures. We find significant differences in function and dietary ecology between two ofthe earliest mammaliaform taxa, Morganucodon and Kuehneotherium-taxa that are central to the debate on mammalian evolution. Morganucodon possessed comparatively more forceful and robust jaws and consumed 'harder' prey, comparable to extant small-bodied mammals that eat considerable amounts of coleopterans. Kuehneotherium ingested a diet comparable to extant mixed feeders and specialists on 'soft' prey such as lepidopterans. Our results reveal previously hidden trophic specialization at the base of the mammalian radiation; hence even the earliest mammaliaforms were beginning to diversify-morphologically, functionally and ecologically. In contrast to the prevailing view, this pattern suggests that lineage splitting during the earliest stages of mammalian evolution was associated with ecomorphological specialization and niche partitioning.%哺乳动物Morganucodon和Kuehneotherium,它们正在一个小岛上捕猎其喜欢的猎物，这个小岛是它们与自己的猎物共享的，在今天南威尔士的格拉摩根。生活在距今2亿年前后的晚三叠纪和早侏罗纪的这些最小的哺乳动物非常小，过去经常被假设是一般的食虫动物。现在,对Morganucodon和Kuehneotherium所做的一项详细研究显示，即便是在那么早的时候，生境分割和饮食专门化就已经在发生了。对牙齿磨损和下颌生物力学所做的分析显示，Morganucooton具有强有力的下颌，能够将甲虫等硬猎物咬碎，但Kuehneotherium却适应了去捕捉较软的猎物，如本期封面所示的蝎蛉。
机译：哺乳动物的起源和辐射是生命史上的重要事件，化石将其起源于三叠纪晚期的2.2亿年前。最早的哺乳动物，代表其进化的前5000万年，包括最基础的分类群，被普遍认为是食虫动物。这意味着，哺乳动物辐射的第一阶段与化石记录中重要创新的出现有关，如异齿牙列，双齿牙结石和齿－鳞状颌骨联合，已从生态形态多样化中分离出来。后来中生代哺乳动物的非常完整的标本的发现显示出比以前怀疑的更大的生态形态多样性，包括对游泳，挖洞，挖掘甚至滑行的适应，但是早期哺乳动物的这种保存完好的化石不存在，并且对其生态形态多样性进行了有力的分析以前一直缺乏。在这里，我们介绍使用同步加速器X射线断层扫描进行的综合分析结果，并对生物力学，有限元模型和牙齿微磨损纹理进行分析。我们发现两种最早的哺乳动物形态类群，Morganucodon和Kuehneotherium-taxa之间在功能和饮食生态学上存在显着差异，这在关于哺乳动物进化的辩论中至关重要。与吃大量鞘翅目的现存小体哺乳动物相比，Morganucodon的下颌相对较有力且结实，并且消耗“较硬”的猎物。 Kuehneotherium的饮食与现存的混合饲养者和鳞翅类等“软”猎物的专家相当。我们的结果揭示了以前隐藏在哺乳动物辐射基础上的营养特化。因此，即使是最早的哺乳动物，也开始在形态，功能和生态上多样化。与普遍观点相反，这种模式表明哺乳动物进化的最早阶段的谱系分裂与生态形态学专业化和生态位分配有关。％哺乳动物Morganucodon和Kuehneotherium，它们正在一个小岛上捕猎其喜欢的猎物，这个小生活在距今2亿年前后的晚三叠纪和早侏罗纪的这些最小的微小非常，过去经常被假设是是岛与这些自己的猎物共享的，在今天南威尔士的格拉摩根。现在，对Morganucodon和Kuehneotherium处理的一项详细研究显示，即使是在那么早的时候，生境分割和饮食专门化就已经在发生了。对牙齿磨损和下颌生物力学工作的分析显示，Morganucooton具有抵抗力的下颚，能够将甲虫等硬猎物咬碎，但Kuehneotherium却适应了去捕捉较软的猎物，如本期封面所示的蝎蛉。

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  • 来源
    《Nature》 |2014年第7514期|303-305B1|共4页
  • 作者

    Pamela G. Gill; Mark A. Purnell; Nick Crumpton; Kate Robson Brown; Neil J. Gostling; M. Stampanoni; Emily J. Rayfield;

  • 作者单位

    School of Earth Sciences, University of Bristol, Wills Memorial Building, Queens Road, Bristol BS8 1RJ, UK;

    Department of Geology, University of Leicester, University Road, Leicester LE1 7RH, UK;

    School of Earth Sciences, University of Bristol, Wills Memorial Building, Queens Road, Bristol BS8 1RJ, UK,Natural History Museum, Cromwell Road, London SW7 5BD, UK;

    Department of Archaeology and Anthropology, University of Bristol, Woodland Road, Bristol BS8 1UU, UK;

    School of Earth Sciences, University of Bristol, Wills Memorial Building, Queens Road, Bristol BS8 1RJ, UK,Ocean and Earth Science, National Oceanography Centre, University of Southampton, Southampton SO14 3ZH,UK;

    Swiss Light Source, Paul Scherrer Institute, CH-5232 Villigen, Switzerland,Institute for Biomedical Engineering, University and ETH Zuerich, Gloriastrasse 35, CH-8092 Zuerich, Switzerland;

    School of Earth Sciences, University of Bristol, Life Sciences Building, 24 Tyndall Avenue, Bristol BS8 1TQ, UK;

  • 收录信息 美国《科学引文索引》(SCI);美国《工程索引》(EI);美国《生物学医学文摘》(MEDLINE);美国《化学文摘》(CA);
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