A new early diverging thalattosuchian (Crocodylomorpha) from the Early Jurassic (Pliensbachian) of Dorset, U.K. and implications for the origin and evolution of the group
A new early diverging thalattosuchian (Crocodylomorpha) from the Early Jurassic (Pliensbachian) of Dorset, U.K. and implications for the origin and evolution of the group
复制标题
来自英国多塞特郡早侏罗世（普林斯巴赫阶）的一种新的早期分化海鳄目（鳄形目）及其对该类群起源和进化的影响
DOI：
10.1080/02724634.2022.2161909
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发表时间：
2022
影响因子：
1.4
通讯作者：
Benson, Roger B.
中科院分区：
文献类型：
--
作者：
Wilberg, Eric W.;Godoy, Pedro L.;Griffiths, Elizabeth F.;Turner, Alan H.;Benson, Roger B.
在主龙类中，海鳄目鳄形类经历了最广泛的海洋适应。尽管受到极大关注，该群体的系统发育地位仍然不确定。海鳄目或者是鳄鱼目、中真鳄目的姐妹群，或者是长鳄类的巢穴。最早确定的海鳄目是托阿克亚目，并且已经拥有该类群的许多共源性。所有的系统发育假说都暗示着一个幽灵谱系至少延伸到了斯内穆里亚人，并且缺乏更古老或更相似的形式可能导致该群体的系统发育位置不确定。在这里，我们描述了一个新物种，Turnersuchus hingleyae，gen。等11 月，来自查茅斯泥岩组（英国多塞特郡）的早期普林斯巴阶箭石泥灰岩成员。该标本包括部分铰接的颅骨、下颌骨、轴向和阑尾元件。根据以下特征，可将其归属于海鳄亚目：鳞状后外侧角有明显的窝；耳枕骨的宽腹外侧突覆盖方体的背面；颞上窗孔较大，缺乏扁平的颅骨台；广泛暴露的益生菌；方形骨的眶突缺乏与脑壳的骨附着。该标本代表了目前从诊断材料中已知的最早的海鳄类。对两个已发表的数据集的系统发育分析发现，特纳鳄是最早分化的海鳄亚目，也是远龙亚科+亚喙鳄亚科的姐妹。贝叶斯尖端年代分析表明，根据拓扑结构，海鳄亚目与其他鳄形类存在雷蒂亚或西尼穆里亚的分歧，置信区间从诺里安到普林斯巴赫。新标本扩展了海鳄亚目的化石记录，但时间尺度分析表明，仍然存在重要的幽灵谱系。
Among archosaurs, thalattosuchian crocodylomorphs experienced the most extensive adaptations to the marine realm. Despite significant attention, the phylogenetic position of the group remains uncertain. Thalattosuchians are either the sister-group to Crocodyliformes, basal mesoeucrocodylians, or nest among longirostrine neosuchians. The earliest definite thalattosuchians are Toarcian, and already possess many synapomorphies of the group. All phylogenetic hypotheses imply a ghost lineage extending at least to the Sinemurian, and a lack of older or more plesiomorphic forms may contribute to the uncertain phylogenetic placement of the group. Here we describe a new species,Turnersuchus hingleyae, gen. et sp. nov., from the early Pliensbachian Belemnite Marl Member of the Charmouth Mudstone Formation (Dorset, U.K.). The specimen includes partially articulated cranial, mandibular, axial, and appendicular elements. It can be attributed to Thalattosuchia based on the following features: distinct fossa on the posterolateral corner of the squamosal; broad ventrolateral process of the otoccipital covering the dorsal surface of the quadrate; large supratemporal fenestrae lacking a flattened skull table; broadly exposed prootic; orbital process of quadrate lacking bony attachment with the braincase. This specimen represents the earliest thalattosuchian currently known from diagnostic material. Phylogenetic analyses of two published datasets recoverTurnersuchusas the earliest diverging thalattosuchian, and sister to Teleosauroidea + Metriorhynchoidea. Bayesian tip-dating analyses suggest a Rhaetian or Sinemurian divergence of Thalattosuchia from other crocodylomorphs, depending on topology, with confidence intervals spanning from the Norian to the Pliensbachian. The new specimen extends the fossil record of Thalattosuchia, but the time-scaling analyses demonstrate that a significant ghost lineage remains.