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Odontocetes-About 30 Million Years Ago
Odontocetes are toothed whales, in which there are two families: the porpoises and the dolphins, with the sperm whale being the only one to not fit into either category. All odontocetes are pack animals that hunt together; they use echolocation to find food and look at their environment. These animals have teeth and one external blowhole, which puts them apart from baleen whales. They are said to be some of the most intelligent animals out there. -
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Mysticetes-About 35 Million Years Ago
Mysticetes eat krill, plankton, and small fish and they use low frequency sounds to communicate over long distances. These animals have a variety of sizes from little, such as the minke whale at 4 meters, to large, like the blue whale which can grow to 25 meters. Instead of teeth, mysticetes have a series of horny plates, baleen, which is made from the same materials as human hair and fingernails and they are used to filter the small bits of food from the water. -
41
Dorudon-About 41 to 33 Million Years Ago
Scientists thought that Dorudons were actually juvenile Basilosaurus but that was later disproved. The Dorudon had big sharp teeth and also ate fish. One species, the Dorudon atrox was about five meters long, had a fluked tail, and small hind limbs. -
45
Rodhocetus-45 Million Years Ago
The Rodhocetus was also from Pakistan and it was about 8 feet long. It differs from modern whales by its teeth (and the fact that it had leg-like limbs) because it had uneven sized teeth throughout whereas modern whales’s teeth are all the same size. Their teeth determined that they fed mainly upon fish. The fat pad in the lower jaw of the Rodhocetus allows directional hearing when underwater which signified that they were well-adapted to the water. -
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Ambulocetus-47 Million Years Ago
The Ambulocetus is like the Pakicetus in that it had four legs and was also located in Pakistan. It differed, however, due to the fact it was about 11 to 12 feet long and had strong limbs which likely inhibited it from actually walking well on land. It had squat legs that splayed from its body, flipperlike hind feet, and it weighed about 400 pounds. On land, it is probable that they had to move like sea lions do, by dragging their bodies with their limbs. -
50
Pakicetus-50 Million Years Ago
It is known as “the first whale” even though it had four legs and lived almost (some say 48) 50 million years ago; we also know that it was located where modern-day Pakistan is. It was the size of a wolf with a carnivorous diet, including some fish. It exhibited characteristics of whales, dolphins, and others; this is shown when paleontologists found it and it had the body of a land animal but the distinctive skull shape of a whale.
