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by MariamMoftah
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•Pakicetus was discovered in 1983 by paleontologists Philip. D. Gingerich and his assistants: Donald. E. Russell, Neill Wells and S. M. Ibrahim Shah in the north of Pakistan.•Lived in what we know today as Pakistan around 50 million years ago.•They lived along the borders of the Tethys Sea, a large shallow ocean, in between the mainland of Asia and Europe to the north and Africa, Arabia, Madagascar, and the Indian subcontinent to the south. •In 1990, Gingerich found another fossil in the Zeuglodon Valley in Egypt.•The complete fossil was found in 2001.•Fossils reveled that Pakicetus had an ankle bone that showed its connection to even-toed mammals that walk on land. Some even-toed mammals or artiodactyls include hippos, pigs, sheeps, cows, deer, giraffe, antelopes, and even cetaceans; the only aquatic artiodactyls.

•Its ear structure is more developed for hearing in the air rather than water. This shows that it spend more time on land then in water. •It had a body of a land mammal but a long distinctive skull shape of a whale’s. •In whales, the ear region of the skull is used for directional hearing underwater. While Pakicetus can use it as both a terrestrial and an aquatic animal.•Pakicetus didn’t have two important adaptations that modern whales have: oEars containing large sinuses that can be filled with blood, allowing them to dive in deep water. oThe ability to hear underwater by sound vibrations. •Other unique features to whales are the folding in a bone of the middle ear and the arrangement of cusps on the molar teeth.

•What makes Pakicetus the earliest whale within the whale evolution is that it had the same ear bone within the skull as a modern day whale. •Another trait is that the eyes of Pakicetus are on top of their heads, which is common in species that live underwater for them to look up. •They had long tails which would have aided them when swimming. •According to chemical evidence, Pakicetus was a wolf-sized animal that fed on meat and fish. •It had a diet primarily of fish, but was a four-footed terrestrial land mammal.•Pakicetus was estimated to have a body mass at 45kg and a body size up to one meter.• The reason why pakicetus is extinct is unknown.

•Some of the many possible descendents are: Ambulocetus: Ambulocetus was larger than Pakicetus, and had paddle-like feet and a large, muscular tail. It was clearly adapted to swimming, but it also had functional legs and a skeleton that allowed it to walk on land. They lacked a blowhole, but the other skull features qualify Ambulocetus as a cetacean. Rodhocetus: Evolved closer to a marine animal than a terrestrial. The ear region of the skull had become more specialized to hearing under water. It could barely walk on land. Developed a tail for swimming. Basilosaurus: An animal completely adapted to an aquatic environment that lost the ability to walk on land. Uses its sturdy flippers and long, flexible body to move in water. Dorudon: lacked the elongated vertebrae of Basilosaurus and was much smaller. The blowhole had moved toward the top of the head. Forelimbs became flippers and the hindlimbs were limited. The tails movement became stronger. This group of whales came to live in all oceans around the world. •None of these animals are a direct ancestor of whales that we know today; they are part of the family tree branches. The important thing is the similarity and differences between each ancestor and the fossil records that help us observe how each adapt to their environment.






Link to evolution unit:Pakicetus is part of the evolution of whales in fact it is known as the “first whale.” In this unit we took that if organisms have similar homologous structures, analogous structures, etc. that means they are related or have a common ancestor to one another. Having a common ancestor proves that evolution happens. Since Pakicetus have similar homologous structures with their descendents this proves that Pakicetus evolved into its descendents. In the evolution unit we took how organisms are all related and this appears in the whale evolution where whales have similarities which classify them together.



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