Widespread azendohsaurids (Archosauromorpha, Allokotosauria) from the Late Triassic of western USA and India
Widespread azendohsaurids (Archosauromorpha, Allokotosauria) from the Late Triassic of western USA and India
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DOI：
10.1002/spp2.1413
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发表时间：
2021-12
影响因子：
2.3
通讯作者：
S. Nesbitt;M. Stocker;M. Ezcurra;N. Fraser;A. Heckert;W. Parker;B. Mueller;S. Sengupta;S. Bandyopadhyay;A. Pritchard;A. Marsh
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文献类型：
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作者：
S. Nesbitt;M. Stocker;M. Ezcurra;N. Fraser;A. Heckert;W. Parker;B. Mueller;S. Sengupta;S. Bandyopadhyay;A. Pritchard;A. Marsh
原型龙类爬行动物经历了快速的谱系多样化，增加形态和身体大小的差异，并扩展到新的适应性景观。几个主要的早期主龙形类分支（例如喙龙）很容易与其他分支区分开来，因为它们的身体类型，而更像蜥蜴和食肉形式的长脖子（例如tanystropheids）在历史上都被归入原龙类或原蜥形目。然而，现在很清楚，这些群体是多系的，蜥蜴状的食肉形式是原始龙形类的近形，并且多个亚支开始于该身体计划。在这些早期的种类中，有一种是来自印度上三叠世的马勒里龙（M. robinsonae）和美国西南部的上三叠统（M. langstoni）。在本文中，我们批判性地重新评估属。我们发现这两个种属都是有效的，并将马里龙属确认为一个早期分化，但晚期存活的食肉性成员，属于阿森多龙科，属于异特龙类。我们对小型和大型个体肢骨的个体发育变化进行的组织学分析和评估表明，小型个体的骨骼生长缓慢，并通过个体发育变得更加健壮，马勒里龙和类似马勒里龙的分类群是奥蒂斯哈尔基亚-阿达曼阶的常见成员，（卡尼晚期到诺利中期）动物群组合来自美国西南部的上三叠世地层，但它们不存在于更年轻的雷维尔期全时带。来自北美洲西部的标本显示，在中三叠世至晚三叠世的大部分时间里，异特龙类都有接近盘古大陆的分布。
Archosauromorph reptiles underwent rapid lineage diversification, increases in morphological and body size disparity, and expansion into new adaptive landscapes. Several of the primary early archosauromorph clades (e.g. rhynchosaurs) are easy to differentiate from others because of their characteristic body types, whereas the more lizard‐like and carnivorous forms with long necks (e.g. tanystropheids) were historically all relegated to the groups Protorosauria or Prolacertiformes. However, it is now clear that these groups are polyphyletic and that a lizard‐like, carnivorous form is plesiomorphic for Archosauromorpha, and multiple subclades started with that body plan. Among these early forms is Malerisaurus from the Upper Triassic of India (M. robinsonae) and the Upper Triassic of south‐western USA (M. langstoni). In this paper, we critically re‐evaluate the genus. We find both species of Malerisaurus as valid, and identify Malerisaurus as an early diverging, but late‐surviving, carnivorous member of Azendohsauridae within Allokotosauria. Our histological analysis and assessment of ontogenetic changes of limb bones of small and large individuals demonstrate that the skeletons of the small forms grew slowly and became more robust through ontogeny, and that the larger recovered bones are at or near the maximum size of the taxon. Malerisaurus and Malerisaurus‐like taxa were common members of the Otischalkian–Adamanian (late Carnian to mid‐Norian) faunal assemblages from Upper Triassic strata of the south western USA, but they are absent from the younger Revueltian holochronozone. Specimens from western North America show that Allokotosauria had a near‐Pangaean distribution for much of the Middle Triassic to Late Triassic.