Jetdarter

The Jetdarter is one of Darwin IV's most bizarre aerial lifeforms. They are small, iridescent scavengers, feeding on the unfinished remains of any creature killed by another predator (such as by a Skewer), and have evolved a compact body that assumes a dart-like shape. Surprisingly for an aerial species, they have no wings whatsoever to aid them in flight. Instead, they possess a biological version of a ramjet engine - complete with a turbine of bone and gristle - which is capable of launching them up to speeds of 40 miles per hour. When at rest, it uses two legs, which otherwise fold up during flight. Jetdarters form nests in the pocket-forests and fear many predators, such as Electrophyte flora and Finned Snappers. They travel in schools, constantly changing their colors in relation to the direction of light.

Trivia

 * In Alien Planet they are portrayed as not having legs.