The fossil Pakicetus is of late early Eocene age from Pakistan. This mammal was 3 to 6 feet long (wolf size). It has a particular ankle bone that links it to articodactyls (a diverse group of even-toed hoofed mammals, including pigs, sheep, cows, deer, giraffes, antelopes, and hippos). Pakicetus had a squat, wolf-size body, with hoofed feet capable of running. Pakicetus also has, however, an ear bone with a feature unique to whales (cetaceans). Additionally it has a long skull with long jaws that resemble that found in whales. Like other artiodactyls its teeth consisted of insisors, canines, premolars (although rather widely spaced and very triangular), and molars. Some specialists claim that Pakicetus was semi-aquatic, but others claim that it lived entirely on land.
Pakicetus (wolf size).
Body view (approximately 6 feet long) and head shot of the same specimen of Pakicetus attocki Gingerich and Russel, 1981, late early Eocene, Pakistan. Natural History Museum of Los Angeles County, Southern California, Age of Mammals Hall.
Since 1981, skeletons similar to, but different from, Pakicetus have been found in early and middle Eocene deposits in Pakistan, India, Egypt, and the southeastern United States. These skeletons have allowed paleontologists and evolutionary biologists to recognize new genera that collectively show a gradual evolutionary transition of Pakicetus-like animals becoming, over time, more like whales (e.g., a few even had their back legs become flippers used for swimming). All these genera, along with Pakicetus, are commonly referred to as archaeocetes [=close ancestors to whales], with Pakicetus the earliest one. In Egypt, by the late Eocene, at least one archaeocete, a Basilosaurus, had a very long, whale-like body (25 m long!).
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