Pileus scalation patterns in squamates. Left: Traditionally hypothesized homologies of scales between different squamate clades. Identities become clear only when the scales are large, forming scutes. Diagrams after Ursel (1978) and Gauthier et al. (2008) for Xantusia. Right: The typical pattern of pileus scutes of snakes appears in the boa Chilabothrus, nested in a clade where the likely ancestral condition was with granular scales. The same scutes can be identified in the Chilobothrus and the distantly related python Malayopython. Phylogeny after Reynolds et al. (2014) and Burbrink et al. (2020). Numbers at the nodes are the divergence times in Ma after Burbink et al. (2020).