Dolphins, along with whales and porpoises, are descendants of terrestrial mammals, most likely of the Artiodactyl order. The ancestors of the modern day dolphins entered the water roughly fifty million years ago, in the Eocene epoch.
Hind limb buds are apparent on an embryo of a spotted dolphin in the fifth week of development as small bumps (hind limb buds) near the base of the tail. The pin is approximately 2.5 cm long.
Modern dolphin skeletons have two small, rod-shaped pelvic bones thought to be vestigial hind limbs. In October 2006, an unusual bottlenose dolphin was captured in Japan; it had small fins on each side of its genital slit, which scientists believe to be a more pronounced development of these vestigial hind limbs.
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Dolphin - Evolution ( recorded by
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Inland North American http://en.wikipedia.org/wiki/Inland_North_American
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