First collected in southwestern Wyoming in a fossil site known as the Green River Formation, Eocypselus rowei lived about 50 million years ago. It was a small creature about 12 cm long (from head to tail), and weighed less than an ounce... The fossil is unusual in having exceptionally well-preserved feathers, which allowed the researchers to reconstruct the size and shape of the bird’s wings in ways not possible with bones alone. Feathers account for more than half of the bird’s total wing length... The analysis suggests that the bird was an evolutionary precursor to the group that includes today’s...
