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Traits of lizards of the world: Variation around a successful evolutionary design

Lizards form a remarkable radiation of land vertebrates. The basic tetrapod design, of a four‐legged sprawling‐postured ectothermic animal, has been highly successful ever since vertebrates first moved to land. Together with the amniote adaptations for fully terrestrial lives it has set crown group squamates on a path to ecological and evolutionary success since they evolved over 200 million years ago (Evans, 2003; Zheng & Wiens, 2016). Over this time period lizards have diversified into all terrestrial habitats except the coldest ones (but see Berman, Bulakhova, Alfimov, & Meshcheryakova, 2016), filling multiple ecological niches, and showing a remarkable array of adaptations. Lizards have repeatedly evolved legless forms (e.g., Brandley, Huelsenbeck, & Wiens, 2008; Gans, 1975), including the hugely successful and highly derived, group of snakes ‐ comprising over a third of the total diversity of squamates (Uetz, 2018). Even without snakes, over 6,650 species of lizards (here including the amphisbaenians) are nowadays recognized (Uetz, 2018), and about 120 new forms are added to the list yearly (Meiri, 2016). This makes lizards more species rich than all of the Mammalia (6,369 species, with 83 species on average, added per year since 2005; Burgin, Colella, Kahn, & Upham, 2018). This extraordinary radiation has made lizards a highly studied model system for evolutionary (e.g., Gamble, Greenbaum, Jackman, Russell, & Bauer, 2016; Losos, 2009; Losos, Jackman, Larson, Queiroz, & Rodriguez‐Schettino, 2009; Rabosky, Donnellan, Talaba, Received: 21 June 2017 | Revised: 13 May 2018 | Accepted: 22 May 2018 DOI: 10.1111/geb.12773