A new dinosaur relative found in Tanzania is the oldest known creature of its kind—a discovery that pushes back the origin of dinosaurs by at least ten million years, paleontologists say.

Dubbed Asilisaurus kongwe, the Labrador retriever-size creature was a silesaur, the closest relatives to true dinosaurs. The new found animal lived 243 million years ago, during the middle Triassic period. Since silesaurs and true dinosaurs diverged from a common ancestor, the two groups should have existed during the same time frame. 

Parts of at least 12 Asilisaurus skeletons were found in 2007 in southern Tanzania's Ruhuhu Valley. With no intact specimen to study, Sidor and his team had to piece together a composite skeleton. What emerged looked nothing like what paleontologists had imagined. Instead of resembling the "typical hatchet-headed, blade-toothed meat-eaters," Asilisaurus was a light, slender-limbed animal with peg-like teeth and a small beak-like structure on its jaw, the University of Maryland's Holtz said.

It's unknown why the lush, wet valleys of prehistoric Tanzania produced so many strains of dinosaur relatives, paleontologists say.

Read the uncut story at NationalGeographic.com