Superbly fossilized remains of a new species of bird thought to be a precursor to modern hummingbirds and swifts have been discovered by researchers examining a fossil collection from Wyoming.
The nearly complete, palm-sized skeleton of the bird is being lauded for its exceptionally well-preserved feathers, which enable the researchers to reconstruct the size and shape of the bird's wings in ways not possible with bones alone.
The bird, named Eocypselus rowei, lived roughly 50 million years ago.
The tiny bird was only 12 centimeters from head to tail; feathers account for more than half of the bird's total wing length.
Scientists have long been puzzled over how swifts and hummingbirds came to be. The two bird species are closely related but have different wing shapes.
Hummingbirds have short wings relative to their bodies, which makes them good at hovering in mid-air. Swifts have super-long wings for gliding and high-speed flight. But the wings of E. rowei were somewhere in between.
"[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," said lead author Daniel Ksepka of the National Evolutionary Synthesis Center in Durham, North Carolina.
To find out where the fossil fit in the bird family tree, the researchers compared the specimen to extinct and modern day species. Their analyses suggest that the bird was an evolutionary precursor to the group that includes today's swifts and hummingbirds.
Finding fossil relatives like this specimen is key to figuring that out, the researchers say.
"This fossil bird represents the closest we've gotten to the point where swifts and hummingbirds went their separate ways," Ksepka said.