A new evolutionary analysis has shown that skin bones in reptiles developed independently across multiple lizard lineages rather than from a single ancestor. Researchers traced the trait over 320 million years using fossils and computational methods. Australian goannas stand out for losing the armor and then regaining it millions of years later.
The study, published in the Biological Journal of the Linnean Society, combined data from 643 living and extinct species. It determined that most lizards first acquired osteoderms more than 100 million years ago during the Late Jurassic and Early Cretaceous periods. These bony structures likely aided survival amid changing climates and predators at the time of dinosaurs such as Brachiosaurus and Stegosaurus.