Figure 1. Comparison of gene families and the phylogenetic tree.

(a) Venn diagram showing unique and overlapping gene families in the baiji, common bottlenose dolphin, dog, human, and mouse. (b and c) Phylogenetic tree and divergence times estimated for the baiji and other mammals. Numbers associated with each terminal branch in light blue are mean rates of synonymous substitution values (rS). Numbers associated with each branch designate the number of gene families that have expanded (green) and contracted (red) since the split from the common ancestor. Triangle arrows and the numbers under them denote the most recent common ancestor (TMCRA), and the scale units are million years ago. The standard error range for each age is represented by the dashed line. The red solid circles on the branch nodes denote the node as an ‘age constraint’ used in the estimation of the time of divergence.