The timeline of the Blue Whale...
Pakicetus- 48million years ago The Pakicetus was a land mammal that was 6 feet long and lived by streams and rivers. They were carnivorous and prayed on fish from in the river and scientist believed they dove in and caught fish similar to how bears hunt. Their nostrils were quite far forward on their heads and their ears evolved to hear underwater. Ambulocetus- 47 million years ago The Ambulocetus was an alligator like creature that sent most of its time on land however fed and spent some time in the water. They were 14 feet long and had shorter legs and webbed feet. Malacetus- 46 million years ago The Malacetus was a sea lion like creature that was 10 feet long and spends less time on land and more time in the sea or in rivers. This allowed them to pend more time hunting and feeding. Dorudon- 37 million years ago The Dorudon was fully aquatic and 15 feet long and its nostrils have now shifted further up its head. Their forelimbs have also now evolved into flippers to help it swim better and move easier in the water. The hind limbs have also drastically shrunken and the tail has formed a fluke (the flat end to the tail). Llanocetus- 34 million years ago The Llanocetus has now grown to 33 feet long and their teeth have reduced in size. As well as this, the beginnings of baleen (the filters in a whales mouth to filter out krill from water) The nostrils have moved even further back into the head. They do still have elbows however are immobile, and the hind limbs can be found on modern whales today. Why did they evolve? Scientist believe that they evolved because of food. Their primary food source was fish and so they evolved to be better at hunting them, which led them to live entirely in the water. Information from: http://ocean.si.edu/ocean-videos/evolution-whales-animation |
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