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

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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.