The streamlined semiaquatic surfbat is descended from a conventional flying bat ancestor. Its flippers, formed from what were once wings, have become stubby and muscular.
The surfbat, Remala madipella, is a flightless, semiaquatic, sea lion-like noctilionoid bat from the seaside beaches of Batavia, from After Man: A Zoology of the Future.
The Batavian beaches are home to packs of surfbats that fish in the shallow waters around the coral reefs. Their hind legs, wings and tail flaps have developed into swimming and steering organs and their bodies have become sleek and streamlined. Their evolution from a flying, through a strictly terrestrial walking form, into an semiaquatic creature is very similar to the evolutionary development of the penguin.
On land the surfbat leaps along on its tail and forelimbs. When resting its tail is curled under its body.