Figure 3.

Extrapolation of number of ancient (U, N and P) orthologs to Urbilateria. The regression lines (and their 90% confidence intervals) are drawn using the number of U, N and P orthologous groups in current species, the estimates for putative ancestors, including the inferred number of losses (Figure 1), and the assumed split of insects and vertebrates about 600 MYA against the species radiation time. Remarkably, the naïve counting of orthologous groups that have at least one insect and at least one vertebrate member results in 7,114 likely Urbilateria genes.