Flipper (anatomy)

Some flippers are very efficient hydrofoils, analogous to wings (airfoils), used to propel and maneuver through the water with great speed and maneuverability (see Foil).

Swimming appendages with the digits still apparent, as in the webbed forefeet of amphibious turtles and platypus, are considered paddles rather than flippers.

[3] For all species of aquatic vertebrates, swimming performance depends upon the animal's control surfaces, which include flippers, flukes and fins.

[4] The evolution of flippers in penguins was at the expense of their flying capabilities, in spite of evolving from an auk-like ancestor that could 'fly' underwater as well in the air.

Flippers are one of the principal control surfaces of cetaceans (whales, dolphins and porpoises) due to their position in front of the center of mass, and their mobility which provides three degrees of freedom.

The whale's surprising dexterity is due primarily to its non-conventional flippers, which have large, irregular looking bumps called tubercles across their leading edges.

[3] A 2007 study of Steller's sea lion found that a majority of thrust was produced during the drive phase of the fore flipper stroke cycle.

[8] Whales and their relatives have a soft tissue flipper that encases most of the forelimb, and elongated digits with an increased number of phalanges.

Modifications to signals in these tissues likely contributed to the origin of an early form of hyperphalangy in fully aquatic cetaceans about 35 million years ago.

The process continued over time, and a very derived form of hyperphalangy, with six or more phalanges per digit, evolved convergently in rorqual whales and oceanic dolphins, and was likely associated with another wave of signaling within the interdigital tissues.

[13] Use of the flippers for foraging behavior is observed in marine mammals such as walruses, seals, and manatee, and even in reptiles such as sea turtles.