‘Dinosaurs Among Us’ at American Museum of Natural History, Selected by Mark Dion

Lithornis is a close relative of ostriches and emus, but it could fly. It was once thought that large, flightless birds like ostriches were a separate evolutionary group from flying birds. But in fact, all birds alive today—even ostriches, emus, and other hefty ground-dwellers—evolved from smaller, flying birds.

ZHAO CHUANG/COURTESY PEKING NATURAL SCIENCE ORGANIZATION