Mapped is the evolutionary strata gene synteny between sequenced reptile (boa and lizard) and avian species. Each line connects a pair of orthologous genes between species, and different colors of lines represent different strata of genes: S0 (gray), ostrich S1 (yellow), Neognathae S1 (brown), Neoaves S2 (orange), DMRT1 (red). Genomic regions encompassing S0 and S1 have experienced multiple inversions across different species, relocating DMRT1 to the middle of the Z chromosome after the divergence between Neognathae and Palaeognathae. In contrast, genomic regions within Neoaves S2 and S3 show high level of syntenic conservation across species.