Penguins didn’t always wear tuxedos.

At least a large penguin that lived 36 million years ago looked nothing like Fred Astaire stepping out in high society. Nor anything like the house tom all dressed up in black and white with no place to go. Scientists announced Thursday that the fossils of the first extinct penguin to be found with preserved evidence of feathers showed that it had yet to adopt the tuxedo look of living penguins. Its feathers were predominantly reddish brown and shades of gray.

The findings also corroborated previous skeletal evidence that penguins had by then evolved the flippers and body shape for powerful swimming  birds in “aquatic flight,” as scientists characterize their marine behavior. The shapes and dense arrangement of the feathers appeared to stiffen the flippers and streamline and insulate the entire body, the researchers said.

For reasons not yet understood, the scientists said, the familiar color pattern of living penguins, dark coat and contrasting white shirt front, is a much more recent innovation, long after they evolved the feathers and anatomy for a life as expert divers and swimmers in frigid water.

“Before this fossil, we had no evidence about the feathers, colors and flipper shapes of ancient penguins,” Julia A. Clarke, a paleontologist at the University of Texas at Austin, said in a statement. She was the lead author of the report describing the discovery online and in Friday’s issue of the journal Science.