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Transcript of Dolphin Evolution
Pakicetidae precede dolphins, and have four legs. They also have a tail, and are dog-like. They lived on land 48-50 million years ago.
Larger than Pakicetidae. Shaped like a crocodile. Their hind limbs were longer, and they had a pelvis. They walked on land, and lived in shallow near shore environments 42-49 million years ago.
Long narrow skulls. Shark-like, with long low bodies, short limbs, and looked even more like mammalian crocodiles. Walked on land, swam in water, and lived in near shore environments. They were alive 37-49 million years ago.
Shorter tail, wider skull, nasal openings halfway up the snout, and webbed feet. Large fore and hind limbs. Adapted even more into an aquatic life-style, but were still amphibious. Lived 39-47 million years ago.
Larger than Protocetidae, and their hind limbs were strongly reduced. Fore limbs had a broad fan shape, and they likely had a tail fluke.They were completely aquatic, and were alive 36-42 million years ago.
Were alive 35-38 million years ago. Considerably smaller than basilosaurids. Their hind limbs were tiny, and they were aquatic, but lived in freshwater. Mode of locomotion was similar to modern day whales. Proportions of their bodies resembled modern day cetaceans.
Other than the fact that Mysticeti precede dolphins, and that they are among the largest animals on Earth, my research did not turn up any useful information.
Modern day cetacean mammals. There are almost 40 species, and are highly intelligent aquatic mammals that have a "playful" behavior. The common bottlenose dolphin is 8 feet in length and weighs 90 pounds. They live for over 40 years, are gray in color, eat fish and squid, and are toothed. Usually live in social groups of 5 to several hundred.
Some Modern Day Dolphins
Atlantic Spotted Dolphin