AR and thalassemia: The sex chromosomes in these two frogs are believed to have diverged at least ∼89 MYA, and they have three common sex chromosomal genes: SRY-box 3 (SOX3), α thalassemia/mental retardation syndrome X-linked (ATRX), and androgen receptor (Miura, 2017; Denton et al, 2018Preprint).