Although not new to science, the new fossils provide some very significant new information. In particular, previously unknown bones from the tail show that it lacked a tail fluke. On the other hand, it did have large back feet and Uhen suggests that it used them as hydrofoils.
Undulating the body in the hip region was the key factor in the evolution of swimming. The very different body forms seen in the lineage of whales point to very different methods of swimming underwater. Previous studies have proposed a possible process to evolve from the ancestral form, paddling with all four legs, to the modern-day whale in which the tail oscillates up and down.
Living vertebrates that are capable swimmers employ a whole range of different techniques, including five particularly well defined methods: quadrupedal paddling, paddling only using the back legs, undulation of the hips, tail undulation, and tail oscillation. Interestingly, it had been suggested that during whale evolution each of these steps occurred in turn, but that the hip undulation stage might have been by-passed.
Materials provided by Society of Vertebrate Paleontology. The first whales to have flukes lived about 38 million years ago. Before this time, whales paddled around using two feet at the base of their spine.
Flukes allow whales to travel further and move through water faster and with greater agility. A whale uses his flukes to propel himself forward in the water and the flippers at his sides to steer and brake.
As he swims, he moves the fluke up and down like a paddle, pushing himself forward with each stroke. Whales also use their flukes to get food into their mouths. When flick-feeding, a whale uses his fluke to direct a wave of small animals toward his mouth. Kick-feeding is similar to flick-feeding: The whale slaps its pray to move it toward his mouth. Another role of flukes is body temperature control. The flukes' arteries and veins can manipulate blood flow to conserve or release heat.
When a large whale prepares for a deep dive, he arches his back, moving the central part of his body above water to get a better downward angle. The arching gives the whale a humpbacked appearance. There is no corresponding muscle for the downward movement of the tail. The belly muscles are attached to the hypaxial mass and tail, which means that even downward movements of the fluke aid in forward propulsion.
When the whale needs to accelerate, or when it is maintaining a slow, steady speed, it will move its tail in large up and down strokes. However, when it is maintaining a fast, constant speed, it only needs to move its fluke in regular, but relatively small, oscillations.
The bigger the whale is the less energy it needs to propel itself through the water in terms of the proportional amount of calories that it requires to cover certain distances.
Interestingly, the tail can also move albeit to a very limited degree to the left and right.
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