Origin and Early Evolution of Squamates and Their Kin: From Fossils to Genomes

Squamates (lizards, including snakes) are the most diverse group of terrestrial vertebrates on Earth today and have an evolutionary history dating back to at least the Middle Triassic (ca. 242 Mya). Despite their vast taxonomic, morphological, and ecological diversity, understanding their origin has remained a challenging and controversial topic for over a century. Initial studies focused on their patchy early fossil record using morphological data, yielding strongly contrasting hypotheses on squamate early evolutionary trajectories. The past decade has seen a massive overhaul of the subject, due to rapid advances in the areas studying phylogenomics, comparative genomics, phenotypic evolution, and new fossil discoveries. Here, we review advances across all of these fields and how they have been bridging hypotheses previously considered irreconcilable, providing a renewed and synthetic understanding of early squamate evolution. We conclude by discussing new datasets and methods behind these advances and perspectives on how the field will move forward for the next decade.