The dinosaur lineage that evolved into birds shrank in body size continuously for 50 million years. From left to right are: the ancestral neotheropod (~220 Million years old), the ancestral tetanuran (~200 million years old), the ancestral coelurosaur (~175 million years old), the ancestral paravian (~165 million years old), and Archaeopteryx (150 million years old). | Davide Bonnadonna

Getting Small the Key for Dinos that Became Birds

Study reveals the key factor behind the transformation of theropods into high fliers.

July 31, 2014
2:00 PM EDT