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

Dating back 210 million years, Effigia okeeffeae isn’t a dinosaur—it is an archosaur more closely related to crocodiles. Still, scientists think this species, like all archosaurs, had much of the genetic toolkit for producing feathers. That’s because scales and feathers originate from the same type of thickened cells in a developing embryo.

ZHAO CHUANG/COURTESY PEKING NATURAL SCIENCE ORGANIZATION