Dinosaur Graveyard Reveals Oldest T. Rex Relative: Dawn Runner

What may be the earliest known relative of T. rex and all meat-eating dinosaurs has been discovered.

The dog-sized mini-predator would’ve made its future relatives proud as it fed on small dinosaurs and the young of other reptiles, and is now shaking up what scientists had previously learned about the evolution of those extinct giants.

The small, lanky, two-legged carnivore named Eodromaeus murphi — Eodromaeus being Greek for “dawn runner,” murphi in honor of field volunteer Jim Murphy — weighed only 10 to 15 pounds (4.5 to 6.8 kilograms) and measured about 4 feet (1.2 meters) in length from snout to tail. The skeletons of two specimens were discovered side-by-side in 230-million-year-old iron-rich stone in the “Valley of the Moon” at the foothills of the Andes in northeastern Argentina, which was once the southwest corner of the supercontinent Pangaea.

“With a hike across the valley, you literally walk over the graveyard of the earliest dinosaurs to a time when they ultimately dominate,” said researcher Ricardo Martinez, a paleontologist at the National University of San Juan in Argentina.

Science!