WASHINGTON (AP) — Scientists have mapped how a group of fearsome, massive dinosaurs evolved and shrank to the likes of robins and hummingbirds.

Comparing fossils of 120 different species and 1,500 skeletal features, especially thigh bones, researchers constructed a detailed family tree for the class of two-legged meat-eaters called theropods. That suborder of dinos survives to this day as birds, however unrecognizable and improbable it sounds.