Sexual dimorphism in the lizard head width. Relationship between head width and body size across four species of Pholidobolus lizards. Males exhibit disproportionally wider heads compared to females. Only one female was available for P. celsiae sp. nov. Lines denote linear regression, and the coloured shadows indicate the 95% confidence interval of the line slope. Non-overlapping blue and red shadows represent significant differences in the slope of the head width to body size relationship, between males and females.