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How did primitive whales swim?
About early research of primitive whale
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| ⓒWikimedia |
In 1966, Frank Fish, who a biology professor at the West Chester University, reported a study on the swimming of modern aquatic mammals.
Professor Frank Fish conducted a comparative study on six types of swimming methods, including mink and musk mice, sea otters, seals, harp seals and bottlenose dolphin. As a result, musk rats swam with their hind legs moving, while mink and sea otters swam with only their hind legs or using their waist. harp seals and seals use their front fins and tails to gain momentum, while whales use their waist and tail to swim.
On the basis of above mention, Professor Fish hypothesized that mammals swimming in the water evolved five different ways of swimming
The first is how mammals with four feet swim using their bodies like paddling.[Quadrupedal paddling]
Second, they swim using their hind legs attached to the pelvis.[Pelvic paddling]
The third is the method of swimming using the surface of the hind foot and the deformity of the waist [Pelvic undulation]
The fourth is how they swim using the tail movement. [Caudal undulation]
The fifth method is how to swim by vibration their tails. [Caudal Oscillation]
Refute of early research
Researchers concluded that the primitive whale, Ambuloketus, would be close to a "Pelvic enumeration" of swimming using the surface and waist of its hind legs, citing its long, non-long tail and long back feet.
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| C.Wikimedia |
In addition, the Basilosaurus, which is a stage where the length of its hind legs has been reduced in earnest among the more evolved primitive whales, was judged to have been swimming by using its waist.
But the following year, in 2003, University of Michigan Professor Philip D. Gingerich reported a study refuting it.
Professor Gingerich argued that primitive whales used their hind feet to swim, similar to Desmana Moschata, a mole species that was aquatic in water rather than otters or sea otters, and then evolved in a way that used their hind feet and waist, and completely used their tails and waist.
He recounted the differences over how mammals that live in water were breast-fed, along with the results of measuring the length of their necks, waist, forelegs and hind legs, respectively.
In addition, he compared the swimming methods of modern mammals based on the full-body fossils of Rhodocetus and Dorudon, whose entire body is intact among primitive whale fossils.
As a result, it was concluded that the primitive whale used not only its waist but also its hind legs before its hind legs degenerated.
Conclusions on the study of primitive whale
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| C. Wikipedia |
Subsequent studies have since shown that changes in the swimming style of primitive whales have been summarized as follows.
Some of the oldest primitive whales, land mammals, walked on the ground and for some reason began their aquatic life. Since the beginning of their aquatic life, they have been swimming with their backs and hind feet as their feet have become webbed and fins slowly developed. They also used their backs and hind legs to swim while swimming in a mixture of waist and hind legs to minimize the resistance of the current. As the proportion of driving force using the waist and tail has increased, the hind legs are rarely used for swimming.
As a result, the hind legs have deteriorated and the fins on the tail have developed to look like modern whales.
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