近日，英国牛津大学Roger J. Benson等研究人员合作发现，一种蜥蜴的同步辐射断层扫描阐明早期有鳞目动物的解剖结构。2022年10月26日，《自然》杂志在线发表了这项成果。

研究人员报告了来自苏格兰中侏罗纪时代的有鳞目动物Bellairsia gracilis的近乎完整骨骼，该骨骼是用高分辨率同步辐射相位对比断层扫描技术记录的。Bellairsia与冠群的许多特征相同，包括与颅骨运动有关的特征（许多现存有鳞目动物的一个重要功能特征）以及脑壳和肩带的特征。除了这些派生特征外，Bellairsia还保留了推断的祖先特征，包括翼腭接触以及颈部和背侧中心区的存在。系统发育分析有力地支持了Bellairsia作为一个主干有鳞目动物，表明它与现存的gekkotan共享的几个特征是多态性的，与分子系统发育假设一致，即gekkotan是早期分化的有鳞目动物。

研究人员还为神秘的Oculudentavis提供了有把握的支持，即主干有鳞目动物的亲缘关系。这些研究结果表明，悬骨、脑壳和肩腰的功能特征先于其腭部和脊椎特征的起源，并表明先进的主干有鳞目动物作为陆地组合的持久组成部分至少在白垩纪中期就已存在。

据了解，有鳞目动物（蜥蜴和蛇）包括10000多个现存物种，它们的祖先在2.4亿年前与它们最接近的现存近亲斑点楔齿蜥的祖先发生了分歧。然而，由于缺乏化石证据，加上有鳞目系统发育的分子和形态学描述之间的严重冲突，导致有鳞目解剖学的起源和演化组合不确定。

附：英文原文

Title: Synchrotron tomography of a stem lizard elucidates early squamate anatomy

Author: Taanda, Mateusz, Fernandez, Vincent, Panciroli, Elsa, Evans, Susan E., Benson, Roger J.

Issue&Volume: 2022-10-26

Abstract: Squamates (lizards and snakes) include more than 10,000 living species, descended from an ancestor that diverged more than 240 million years ago from that of their closest living relative, Sphenodon. However, a deficiency of fossil evidence1,2,3,4,5,6,7, combined with serious conflicts between molecular and morphological accounts of squamate phylogeny8,9,10,11,12,13 (but see ref.14), has caused uncertainty about the origins and evolutionary assembly of squamate anatomy. Here we report the near-complete skeleton of a stem squamate, Bellairsia gracilis, from the Middle Jurassic epoch of Scotland, documented using high-resolution synchrotron phase-contrast tomography. Bellairsia shares numerous features of the crown group, including traits related to cranial kinesis (an important functional feature of many extant squamates) and those of the braincase and shoulder girdle. Alongside these derived traits, Bellairsia also retains inferred ancestral features including a pterygoid–vomer contact and the presence of both cervical and dorsal intercentra. Phylogenetic analyses return strong support for Bellairsia as a stem squamate, suggesting that several features that it shares with extant gekkotans are plesiomorphies, consistent with the molecular phylogenetic hypothesis that gekkotans are early-diverging squamates. We also provide confident support of stem squamate affinities for the enigmatic Oculudentavis. Our findings indicate that squamate-like functional features of the suspensorium, braincase and shoulder girdle preceded the origin of their palatal and vertebral traits and indicate the presence of advanced stem squamates as persistent components of terrestrial assemblages up to at least the middle of the Cretaceous period.

DOI: 10.1038/s41586-022-05332-6

Source: https://www.nature.com/articles/s41586-022-05332-6