A development of the wing membrane between the hind legs and tail has produced the plunger's powerful swimming paddle. The swimming motion is augmented and steered by the wings, which are strong flaps of gristle. Fatty insulation is reinforced by the sleek pelt of fine pycnofibres, with its striking black and white pattern.
The Plunger, Pinala fusiforme, is a flightless, partly bipedal, semiaquatic, chinstrap penguin-like pterodactyloid pterosaur from the shorelines of the islands near Antarctica, in The New Dinosaurs: An Alternative Evolution.
A windswept chain of rocky islands rises above the green and white swell of the Antarctic waters. On the rock pinnacles, above the height at which waves surge and break, lie a number of glossy shapes, basking in the distant watery sun. These black and white creatures flop around clumsily, seeming to wobble on their bellies, pushed along by their stubby limbs, apparently quite incapable of any fast or graceful movement. Yet, when they reach a cliff edge, they rise to their hind legs and plunge head first into the foam. There they are transformed into elegant streamlined creatures, turning and darting, chasing after the shoals of fish on which they feed. In many areas the seas are so rich in fish that the fishing animals do not need to travel long distances to find them.
The plunger is a fishing pterosaur that has lost its powers of flight. Its wings are still present but modified into hydrodynamic organs that allow it a mobility in the water that its ancestors had in the air. Layers of fat have built up under the skin, and these not only insulate the animal from the chill waters but also give it the streamlined shape that allows it to swim easily. The plunger's lungs have special adaptations to withstand the great pressures found at the depths at which they hunt their food.
For all its aquatic adaptations, the plunger still needs to come ashore to breed. It nests in vast rookeries on isolated rocks, but only in areas where the nearby ocean currents ensure a constant supply of fish.