By studying the fossil record, paleontologists have pieced together a clear picture of the evolution of the whale.
Long ago its ancestors lived on land, so a lot of features had to change over time in order to succeed in an aquatic environment.
Lets look at the evolution of just one of these featuresthe front limb.
This animal may well be an ancestor of the whale.
Look carefully at its front leg (forelimb). There are three parts highlighted with particular colors:
yellow = shoulder blade
red = upper arm
blue & green = lower arm
purple = forefoot