The diagram shows some representative mammals on the timeline of the evolutionary history of modern whales. The first mammal illustrated on the timeline is a fossil terrestrial cetacean, Pakicetus, 1.75m long. Next is an amphibious cetacean of 4.1m in length, Ambulocetus. A typical fossil, fully aquatic cetacean, Dorudon, is 4.5m long. The modern descendants are the baleen whales and toothed whales.