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500
The Pakecitus: 50-60 Million Years Ago
One of the whale's earliest ancestors also belongs to the order cetacea, and is known as pakicetid. It lived near the prehistoric waters of Pakistan some 60 million years ago, and resembled a modern-day wolf -- with hooves. Looks can be deceiving, however, as there were certain traits in pakicetid that have carried over to today's whale: the unique position of the ear bones in the skull (which is only seen in cetaceans), a unique middle-ear bone, and triangular molars. -
Period: 520 to
Whale Evolution: The Walking Whale
Time Scale is in Millions and condensed. -
Dec 1, 650
The Ambulocetus: About 50 Million Years Ago
Ambulocetus was the next step in whale evolution - this "missing link" lived both on land and in the water, and was a carnivore approximately 9 feet long. Its hind legs were adapted to swimming, though it also walked on land. It also had triangular molars. Less noticeable but just as important, its inner ear bone had developed to be able to hear underwater. -
May 1, 710
The Rodhocetus: 45 Million Years Ago
Rodhocetus was a semi-aquatic, primitive whale species that had the ankle bones of an artiodactyl, and the underwater hearing abilities of ambulocetus. It swam using its flipperlike feet and long tail which it used as a rudder. The nasal openings had begun to move up the skull, in what would eventually become the whale's signature spout. (This is known as a "nasal drift.") Its limbs could support them on land as well. -
Feb 1, 1200
The Squalodon: 20 Million Years Ago
Squalodon is an ancestor of the toothed whales, having retained its teeth from millions of years previous, during the time of pakicetid. They lived in warm waters. -
Feb 1, 1500
The Cetotherium: 15 Million Years Ago
Cetotherium is an ancestor of the baleen, or filter-feeding whales (examples include the sperm whale, blue whale and humpback whale). It was smaller than the modern-day baleens, ranging between 10 and 20 feet long. They were hunted by megalodon, the infamous prehistoric shark that grew to 50 feet. -
The Modern Whale: Today
Though many variations are part of the whales' family tree, today's whales are divided into two groups -- toothed and baleen. -
The Basilosaurus: 35-45 Million Years Ago
Basilosaurus was a 50-foot-long sea mammal, though it originally had been mistaken for a lizard (Basilosaurus means "king lizard"). It swam like an eel, but its jawbone, ribs and and small hind limbs make it a mammal. It straddled two worlds; though it only lived in the water, it couldn't dive to any substantial depths, or could its hind limbs support it on land. -
The Dorudon: 40 Million Years Ago
The Dorudon was fully aquatic whales (like Basilosaurus, Dorudon had very small hind limbs that may have projected slightly beyond the body wall). They were no longer tied to the land; in fact, they would not have been able to move around on land at all.
