Distributed under Creative Commons Cc-by 4.0 the Monophyly of Susisuchidae (crocodyliformes) and Its Phylogenetic Placement in Neosuchia
Distributed under Creative Commons Cc-by 4.0 the Monophyly of Susisuchidae (crocodyliformes) and Its Phylogenetic Placement in Neosuchia
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3.6
通讯作者：
A. Turner;A. Pritchard
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作者：
A. Turner;A. Pritchard
尤苏奇鳄，包括所有现存的鳄鱼，历史上以两个解剖特化为特征：一个球窝椎关节和一个广泛的次级硬腭与翼状骨结合的内choana。早白垩世新蜥目蜥科被认为在系统发育上接近真蜥目。假定的苏氏犬种Isisfordia duncani最初被描述为一种过渡形式，表现出这些苏氏犬种特征的早期版本。在这里，我们研究了Isisfordia的形态学方面，并对其推定的姐妹分类群Susisuchus的形态学进行了评论。我们的重新检查支持Isisfordia具有过渡性椎体形态的概念，但我们提出了其腭结构的新解释，表明它比以前认为的更具可塑性。Isisfordia的次脉不是翼状的。相反，长腭在翼状骨下向远端扩张，形成了颏部的前缘，这在许多先进的新苏猿人中很常见。将这些观察结果纳入扩大的新苏轼鳄形动物系统发育数据集，得出了一个新的苏轼科系统发育假说。Isisfordia和Susisuchus形成了一个单系的Susisuchidae，位于Neosuchia的基部附近，而不是Eusuchia的姐妹分类群。
Eusuchian crocodyliforms, which include all living crocodylians, have historically been characterized by two anatomical specializations: a ball-in-socket vertebral joint and an extensive secondary hard palate with a pterygoid-bound internal choana. The Early Cretaceous neosuchian clade Susisuchidae is typically regarded as phylogenetically near Eusuchia. The putative susisuchid Isisfordia duncani was initially described as a transitional form exhibiting incipient versions of these eusuchian traits. Here we examine aspects of the morphology of Isisfordia and comment on the morphology of its putative sister taxon Susisuchus. Our reexamination supports the notion of Isisfordia possessing transitional vertebral morphology but we present a new interpretation of its palate construction that shows it to be more plesiomor-phic than previously thought. The secondary choana of Isisfordia is not pterygoid bound. Instead, long palatines expand distally lapping under the pterygoid to form the anterior border of the choana as is common among many advanced neosuchi-ans. Incorporation of these observations into an expanded phylogenetic dataset of neosuchian crocodyliforms results in a new phylogenetic hypothesis for Susisuchi-dae. Isisfordia and Susisuchus form a monophyletic Susisuchidae that sits near the base of Neosuchia, and is not the sister taxon of Eusuchia.