Institut für Biologie, Humboldt-Universität zu Berlin, 10099, Berlin, Germany.
Museum für Naturkunde, Leibniz-Institut für Evolutions- und Biodiversitätsforschung, Invalidenstraße 43, 10115, Berlin, Germany.
Sci Rep. 2022 Dec 23;12(1):22257. doi: 10.1038/s41598-022-24983-z.
The development of the vertebral column has been studied extensively in modern amniotes, yet many aspects of its evolutionary history remain enigmatic. Here we expand the existing data on four major vertebral developmental patterns in amniotes based on exceptionally well-preserved specimens of the early Permian mesosaurid reptile Mesosaurus tenuidens: (i) centrum ossification, (ii) neural arch ossification, (iii) neural arch fusion, and (iv) neurocentral fusion. We retrace the evolutionary history of each pattern and reconstruct the ancestral condition in amniotes. Despite 300 million years of evolutionary history, vertebral development patterns show a surprisingly stability in amniotes since their common ancestor. We propose that this stability may be linked to conservatism in the constraints posed by underlying developmental processes across amniotes. We also point out that birds, mammals, and squamates each show specific trends deviating from the ancestral condition in amniotes, and that they remain rather unchanged within these lineages. The stability of their unique patterns demonstrates a certain homogeneity of vertebral developmental constraints within these lineages, which we suggest might be linked to their specific modes of regionalization. Our research provides a framework for the evolution of axial development in amniotes and a foundation for future studies.
脊椎的发育在现代羊膜动物中得到了广泛研究，但它的进化历史的许多方面仍然是神秘的。在这里，我们基于保存极为完好的早二叠世中龙目爬行动物中龙的标本，扩展了羊膜动物中四种主要脊椎发育模式的现有数据：（i）椎体骨化，（ii）神经弓骨化，（iii）神经弓融合，以及（iv）神经中枢融合。我们追溯了每种模式的进化历史，并重建了羊膜动物的祖先状态。尽管有 3 亿年的进化历史，但羊膜动物的脊椎发育模式表现出惊人的稳定性，自它们的共同祖先以来几乎没有变化。我们提出，这种稳定性可能与基础发育过程在羊膜动物中所施加的约束的保守性有关。我们还指出，鸟类、哺乳动物和蜥蜴类各自表现出与羊膜动物祖先状态偏离的特定趋势，而且在这些谱系中它们仍然没有太大变化。它们独特模式的稳定性表明，在这些谱系中，脊椎发育约束具有一定的同质性，我们认为这可能与它们特定的区域化模式有关。我们的研究为羊膜动物轴向发育的进化提供了一个框架，并为未来的研究奠定了基础。
