Fig. 2

Quantification of gene origination, duplication, and loss in amniote evolution. Bars beside inner branches of the amniote species tree denote numbers of origination, duplication, and loss of genes per million years scaled by the numbers at the branch (i). Gene origination, duplication, and loss events in the terminal branches are not counted because they can be largely influenced by rampant misidentifications in gene prediction. Additionally, inferred ancestral gene repertoires are shown at internal nodes of the tree. Branch lengths are proportional to inferred divergence times shown in Additional file 5: Figure S3, and the details of these values are included in Table 2. The gene number at the ancestral nodes of birds shown in italics is likely underestimated due to underrepresentation of certain genomic regions in whole genome sequencing [3,4,5]