Data from: An exceptionally preserved Jurassic skink suggests lizard diversification preceded fragmentation of Pangaea

The present distribution of lizards is usually explained as a result of relatively recent global events, i.e. faunal turnovers or exchanges within and between particular continents mostly connected with glaciations and land-bridges. However, today’s disjunct distribution of the North American Xantusiidae and African Cordyliformes (close relatives of skinks) does not fit generally accepted biogeographic patterns. A new exquisitely preserved specimen of the Late Jurassic lizard Ardeosaurus brevipes from the Solnhofen area, Germany sheds some light on the problem. A posterior projection of its parietal is known only in the Dibamidae, Gekkota, and Scincoidea, taxa representing first branches on the molecular tree of lizards. The projection of the parietal is proposed to be an apomorphy of the Squamata that was lost in the common ancestor of Lacertoidea and Toxicofera (snakes, anguimorphs and iguanians). This implies a basalmost position of A. brevipes on the Squamata tree. The location of the supratemporal such as in A. brevipes characterizes all the Scincoidea and some geckos, but most geckos lack osteoderms, which are common in Scincoidea. This makes A. brevipes the oldest known crown-member of this lineage. Moreover, this indicates that the main groups of modern lizards were present already in the Jurassic. Ancestors of Cordyliformes migrated to Gondwana in the Late Jurassic together with dinosaurs, prior to the Cretaceous separation of this ancient continent.

当前蜥蜴类的分布格局通常被归因于较新近的全球性地质事件，即主要与冰川作用及陆桥相连的特定大陆内部及大陆间的动物区系更替或交流。然而，现今北美夜蜥科（Xantusiidae）与非洲环尾蜥目（Cordyliformes，石龙子的近缘类群）的间断分布格局，并不符合学界普遍认可的生物地理模式。一件产自德国索伦霍芬地区的晚侏罗世短脚鹭蜥（Ardeosaurus brevipes）的保存极为精美的标本，为该问题的解析提供了新的线索。其顶骨的后突结构仅见于盲蜥科（Dibamidae）、壁虎下目（Gekkota）以及石龙超科（Scincoidea），这些类群均代表了蜥蜴分子系统树的早期分支类群。该顶骨后突被认定为有鳞目（Squamata）的特有衍征，后在正蜥超科（Lacertoidea）与毒蜥类（Toxicofera，包含蛇、蛇蜥下目类群和鬣蜥类）的共同祖先类群中丢失。这一结论表明短脚鹭蜥在有鳞目系统树上处于基部分支的位置。短脚鹭蜥的颞上骨位置特征与所有石龙超科类群及部分壁虎类一致，但多数壁虎类缺乏在石龙超科中普遍存在的骨板（osteoderms）。这使得短脚鹭蜥成为该演化支已知最古老的冠群成员。此外，该研究结果还表明现代蜥蜴的主要类群早在侏罗纪时期就已出现。环尾蜥目的祖先于晚侏罗世与恐龙一同迁移至冈瓦纳大陆，早于白垩纪该古老大陆的裂解事件。