Four hundred fifty-five million years ago, Earth was a hot place with high sea levels that had flooded many of the landmasses, including what would later become North America. This spreading ocean was ...

Five successive ancestors leading from dinosaurs to modern birds. From left to right: the ancestral neotheropod (220 million years old), the ancestral tetanuran (200 myo), the ancestral coelurosaur ...

The late Cretaceous tyrannosaurid Alioramus altai is known from a single specimen whose articulated braincase exhibits a nearly unique combination of preservational quality, subadult stage of growth, ...