Although evolution has traditionally been assumed to be a slow, gradual process, the fossil record suggests that processes such as global climate change, mass volcanism and asteroid impacts have caused the rapid rise and fall of major groups throughout Earth’s history. Lepidosauria (rhynchocephalians, snakes and lizards) are a diverse group with almost 10,000 living species. They have a long evolutionary history spanning almost 250 million years, during which time they went through two major and several smaller extinction events. The abundance of data available for lepidosaurs make them a model group to use when investigating macroevolutionary processes. Except for regional studies of the demise of snakes and lizards at the Cretaceous-Palaeogene, the survival of lepidosaurs through catastrophic events remains poorly studied. Here we aim to use molecular clock analyses with fossil calibrations to investigate whether the Cretaceous-Palaeogene and Eocene-Oligocene extinction events lead to major adaptive radiations. This will be complemented by the description of new fossil faunas from the Late Cretaceous and Early Eocene. We will also use the fossil record of lepidosaurs to look at their disparity (morphological diversity), focusing on tooth shape and body size, to investigate niche occupation from the Triassic to the Cenozoic. Rhynchocephalians, terrestrial lizards and mosasaurs will be considered, with a focus on the Jurassic-Cretaceous, Cretaceous-Palaeogene and Eocene-Oligocene extinction events. The geographical location of fossil occurrences will also be examined, so as to understand the area various clades originated, and the relative importance of dispersal and vicariance. This study will provide valuable insights into how biodiversity reacts to past, present and future environmental stresses.