Probably the most famous of the Archaeoceti is Basilosaurus, first found in the 1830's in North America. It was originally thought to be a dinosaur (hence the "saurus" in its name). It had a long, snake-like body with a relatively small head. Although it still had its pelvic bones with the bones of its hindlegs, they were greatly reduced, and probably did not show outside of the body. Its nostrils were high up on its skull, coming closer to the nostril position of modern whales. Basilosaurus is the state fossil of both Alabama and Mississippi.
The Odontoceti, or toothed whales, first appear in the fossil record in the late Eocene Period, and probably developed from the Archaeoceti. The Odontoceti make up the majority of our modern whales, and include the sperm whale, beaked whale, pilot whale, killer whale, beluga, narwhal, and porpoises (which include the dolphins).
The Mysticeti, or baleen whales. These whales have lost their teeth, and instead have plates of a fibrous substance called baleen which they use to filter plankton from the water.
The Mysticeti first appear in the fossil record in the early Oligocene Period (36 to 22.5 million years ago). Only eight genera survive today, and all are under severe threat from hunting. They include the blue whale, northern and southern right whale, humpback whale, grey whale, minke whale, bowhead whale, and fin whale.
Let's hope that whales continue to populate our oceans for a long time, allowing us to enjoy watching and listening to them.
In my next article, I will write about another group of mammals that has taken to the ocean: the pinnipeds, or seals and walruses.
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