Although whales are expert swimmers and perfectly adapted to life underwater, these marine mammals once walked on four legs. Their land-dwelling ancestors lived about 50 million years ago. Meet Pakicetus , a goat-sized, four-legged creature that scientists recognise as one of the first cetaceans (the group of marine animals that includes ...

Living whales have no back legs, and their front legs take the form of flippers that allow them to steer. Their special tails provide the powerful thrust necessary to move their huge bulk....

2011年2月10日 · Whales have lost their hind legs (the front ones are now their flippers), and we have a pretty good fossil record of how they did so, thanks in large part to the work of Phil Gingerich of the University of Michigan Museum of Paleontology (see his great whale evolution site here) and his collaborators.

2024年9月4日 · “When their ancestor went back into the water, whales and dolphins lost their hind legs and developed a fish-like body,” said lead author Amandine Gillet, Marie Curie Fellow in the Department of Organismic and Evolutionary Biology at Harvard and in the Department of Earth and Environmental Sciences at the University of Manchester, UK.

2008年9月11日 · Over time, as they evolved to dwell in water, their front legs became flippers while they lost their back legs and hips, although modern whales all still retain traces of pelvises, and...

2000年10月27日 · Indeed, the earliest known whales, which date back as far as 50 million years ago, had well-developed hindlimbs and are believed by most paleontologists to have evolved from four-legged...

2020年8月24日 · Over time, the body becomes more oval-shaped or streamlined. At the same time, the pelvis, or hips, begins to shift the shrinking rear legs into a backward direction. These adaptations create a more hydrodynamic mammal in the water.

The specimen as found had elementary legs protruding from the body about four feet, two inches, covered with blubber about one-half inch thick. Andrews identified the bones as tibia and metatarsal, the cartileges as femur and tarsus, and published his findings:

2013年3月6日 · Like hippos, their closest living relatives, whales are descended from an ancestor that had four legs and walked on land. Paleontologists have found fossil evidence of various “walking whales,” semiaquatic whales that show some early stages of the transition from land-dwelling ancestors to today’s familiar fully marine whales.

2006年5月22日 · — When ancient whales finally parted company with the last remnants of their legs about 35 million years ago, a relatively sudden genetic event may have crowned an eons-long shrinking process.