A tiny new Middle Triassic stem-lepidosauromorph from Germany: implications for the early evolution of lepidosauromorphs and the Vellberg fauna
A tiny new Middle Triassic stem-lepidosauromorph from Germany: implications for the early evolution of lepidosauromorphs and the Vellberg fauna
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DOI：
10.1038/s41598-020-58883-x
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发表时间：
2020-02
影响因子：
4.6
通讯作者：
G. Sobral;T. Simões;R. Schoch
中科院分区：
文献类型：
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作者：
G. Sobral;T. Simões;R. Schoch
中三叠世是全球四足动物群发生重大变化的时期，但这一时期的化石记录在很大程度上对陆生动物群来说是模糊的。这严重限制了我们对代表当今世界上一些最多样化动物群的谱系多样化的最早阶段的理解，例如lepidosauromorphs（例如，蜥蜴和大蜥蜴）。在这里，我们报告了一个微小的新lepidosauromorph从中三叠世从韦尔贝格（德国），它结合了马赛克的功能，从早期发展的鳞和rhynchocephalies，如同时出现的一个压骨和部分发展的acrodonty。系统发育分析采用不同的最优标准，并结合形态和分子数据，一贯恢复新的分类单元作为一个干lepidosauromorph，这意味着干lepidosauromorph物种共同居住的地区，包括今天的中欧在同一时间作为最早的已知rhynchocephalians和squamates。它进一步证明了一个更复杂的演化情景牙齿的演化在早期lepidosauromorphs，独立收购acrodonty早期在其进化史。韦尔贝格的大多数陆生脊椎动物体型较小，这与全球较年轻的三叠纪沉积物形成鲜明对比，但与早三叠世动物群相当，表明该动物群可能存在长期的小人国效应。
The Middle Triassic was a time of major changes in tetrapod faunas worldwide, but the fossil record for this interval is largely obscure for terrestrial faunas. This poses a severe limitation to our understanding on the earliest stages of diversification of lineages representing some of the most diverse faunas in the world today, such as lepidosauromorphs (e.g., lizards and tuataras). Here, we report a tiny new lepidosauromorph from the Middle Triassic from Vellberg (Germany), which combines a mosaic of features from both early evolving squamates and rhynchocephalians, such as the simultaneous occurrence of a splenial bone and partial development of acrodonty. Phylogenetic analyses applying different optimality criteria, and combined morphological and molecular data, consistently recover the new taxon as a stem-lepidosauromorph, implying stem-lepidosauromorph species coinhabited areas comprising today’s central Europe at the same time as the earliest known rhynchocephalians and squamates. It further demonstrates a more complex evolutionary scenario for dental evolution in early lepidosauromorphs, with independent acquisitions of acrodonty early in their evolutionary history. The small size of most terrestrial vertebrates from Vellberg is conspicuous, contrasting to younger Triassic deposits worldwide, but comparable to Early Triassic faunas, suggesting a potential long-lasting Lilliput effect in this fauna.