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Scientists
believe that dolphins evolved from mammals on land. They even believe that
mesonychids, which are hoofed, wolf-like animals about the size of a dog
are their most likely ancestors. Hard to believe, isn't it? And this is how
it happened: the mesonychids lived at the edge of the sea. After millions
of years the descendants of mesonychids spent most of their time in the
water, until finally they became amphibious. As they adapted to
their new way of life, their bodies changed. Their forelimbs became short
broad paddles. Their body became more streamlined because their ears, hind
limbs and hair became less and less obvious. Their tails flattened and
their nostrils or blowholes moved higher on the skull so that they could
breath without totally surfacing. Dolphins were first described by
Aristotle. Aristotle was a Greek philosopher, and a natural scientist. He
first described dolphins and whales in the fourth century B.C. Aristotle
was the first person to classify dolphins and whales as mammals, rather
than fish. Dolphins belong to a group of mammals called cetaceans.
Cetaceans comes from the Greek word cetus, meaning whole. Cetaceans
smaller than 4-5 meters are known as dolphins. All cetaceans breath in
Oxygen to survive, and spend their whole lives underwater. Cetaceans
number some of the largest mammals that have ever existed. The best known
cetacean is the Bottlenosed
Dolphin, which has been popularized by TV
programs, such as Flipper. |
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It's
All Relative |
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Mesonychids
Hoofed
wolf-like animals who are the dolphins' most likely ancestors.
About the
size of a dog. |
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Primitive
toothed whale
These
are the ancestors of dolphins, porpoises, and also whales.
Unlike today's dolphins, they have no dorsal fin.
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Long
nosed Porpoise
The
Long-nosed Porpoise was one of the dolphin's and
porpoise's oldest ancestors. They lived over 12,000 years
ago!
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