Squamate phylogeny and evolution: fossil marine lizards, snakes, and basal terrestrial lizards

蛇是从有肢的蜥蜴进化而来的，这是脊椎动物进化生物学中一个经久不衰的谜。随着新的证据重新引发了关于蛇的起源的争论，这个话题正在重新引起人们的兴趣。有两种截然相反的假设：1)蛇与水生四肢蜥蜴有共同的祖先；蛇与穴居的无肢陆生蜥蜴有着共同的祖先。新数据的收集和分析将集中在现代盲穴居蛇（scolecophidian）上，这种蛇被广泛认为是非常原始的。还将收集和描述来自南美洲、澳大利亚、非洲和中东的白垩纪蛇化石的新数据。来自蜥蜴的新数据将通过研究鲜为人知的白垩纪海洋物种化石（如翼龙、多龙和锥龙），以及研究现代无肢穴居蜥蜴（如双足类和两栖类）来获得。进化关系的模式，或系统发生，将通过构造分支图来产生，这种分支图被称为枝状图，来源于对解剖数据（骨骼、肌肉等）的分析。对化石和现存蛇和蜥蜴的进化关系的研究将阐明产生这些动物迷人的解剖特征的进化模式和过程（例如，无肢体、四肢到鳍、巨型），并进一步测试蛇的水生起源与穴居起源。不断收集和研究新化石，可以修正我们对过去及其生物多样性的认识，并为了解现代世界的组织方式提供洞见。研究现存蛇类和蜥蜴的未描述的解剖结构，特别是穴居蛇类，将有助于确定哪些现存动物群体与它们的原始或早期祖先有最共同的特征。总的来说，这些新数据将通过修改现有的进化树或为新的假设提供额外的支持来完善系统发生。关于蛇和蜥蜴进化的新数据和新观点将对有关这些动物起源的激动人心的辩论作出重大贡献。

The origin and evolution of snakes from limbed lizards is an enduring enigma of vertebrate evolutionary biology. The topic is currently enjoying a revival of interest as new evidence has renewed controversy on the origins of snakes. There are two contrasting hypotheses: 1) snakes share a common ancestor with aquatic limbed lizards; 2) snakes share a common ancestor with burrowing, terrestrial, limbless lizards. Collection and analysis of new data will focus on modern blind burrowing snakes (scolecophidians), widely thought to be very primitive. New data will also be collected and described for Cretaceous-aged fossil snakes from South America, Australia, Africa, and the Middle East. New data from lizards will be obtained by studying poorly known Cretaceous fossil marine species (i.e., aigialosaurs, dolichosaurs, and coniasaurs), and by studying modern limbless, burrowing lizards, known as dibamids and amphisbaenids. Patterns of evolutionary relationship, or phylogenies, will be produced by constructing branching diagrams called cladograms derived from analysis of anatomical data (bones, muscles, etc.). This study of the evolutionary relationships of fossil and living snakes and lizards will illuminate the evolutionary patterns and processes that produced the fascinating anatomical features of these animals (e.g., limblessness, limbs to fins, gigantism), and to further test the aquatic vs. burrowing origins of snakes. Collecting and studying new fossils continually revises our understanding of the past and its biodiversity, and provides insights into how the modern world is organized. Studying undescribed aspects of the anatomy of living snakes and lizards, in particular burrowing scolecophidian snakes, will help to determine what groups of living animals still share most features in common with their primitive, or early, ancestors. Collectively, these new data will refine phylogenies by either modifying existing evolutionary trees, or by providing additional support for new hypotheses. New data and new ideas on the evolution of snakes and lizards will be significant contributions to the exciting debate on the origins of these animals.