Well-preserved fossil feathers have brought an understanding of prehistoric wing shapes in ways not possible with bones alone, U.S. paleontologists say.

Researchers at the National Evolutionary Synthesis Center in Durham, N.C., said a tiny bird fossil discovered in Wyoming offers clues to the precursors of wings of modern birds like swifts and hummingbirds.

The nearly complete skeleton of a bird that would have fit in the palm of your hand and weighed less than an ounce was collected in southwestern Wyoming in a fossil site known as the Green River Formation, an NESC release reported Wednesday.

The 50-million-year-old fossil is unusual in having exceptionally well-preserved feathers, researchers said.

Comparing the specimen to extinct and modern day species suggests the bird was an evolutionary precursor to the group that includes today's swifts and hummingbirds, they said.

Hummingbirds possess short wings relative to their bodies, which makes them good at hovering in mid-air, while swifts have super-long wings for gliding and high-speed flight

The wings of the prehistoric bird, Eocypselus rowei, were somewhere in between, researchers said.

"[Based on its wing shape] it probably wasn't a hoverer, like a hummingbird, and it probably wasn't as efficient at fast flight as a swift," study lead author Daniel Ksepka said.

The shape of E. rowei's wings, coupled with its tiny size -- less than 5 inches from head to tail -- suggest the ancestors of today's swifts and hummingbirds got small before each group's unique flight behavior evolved, he said.

"Hummingbirds came from small-bodied ancestors, but the ability to hover didn't come to be until later," he explained.