Parrington handed over the rocks and fossilised bones to his PhD student Alan Charig, who carried out an initial assessment of the bones in the 1950s and was still working on the project at the Natural History Museum when he died in 1997.
The fossils were then stored away again until they were re-examined by a team from Britain and the United States. They found the creature's arm bones bear the key characteristics of dinosaurs and that it must have grown rapidly, another distinguishing feature of dinosaurs.
The fossils have been dated to between 247 million and 235 million years ago, a geological period known as the Triassic when Africa was part of a giant supercontinent called Pangaea, which included South America, the Antarctic and Australia.
"If the newly named Nyasasaurus parringtoni is not the earliest dinosaur, then it is the closest living relative found so far," said Dr Sterling Nesbitt of the University of Washington in Seattle, who collaborated on the study published in the journal Biology Letters.
"It establishes that dinosaurs likely evolved earlier than previously expected and refutes the idea that dinosaur diversity burst on to the scene in the Late Triassic [period], a burst of diversification unseen in any other groups at that time," Nesbitt said.
Dr Paul Barrett, a dinosaur expert at the Natural History Museum, said: "Although we only know Nyasasaurus from fossil fragments, the anatomy of its upper arm bone and hips have features that are unique to dinosaurs, making us confident that we're dealing with an animal very close to dinosaur origin."
Dinosaur fossils are found throughout the world. However, the discovery confirms that dinosaurs probably originated in the Southern Hemisphere and migrated north, probably with the movement of the continents.
Nyasasaurus parringtoni fossil:
• 247 to 235 million years old
• 10 to 15 million years older than all other dinosaur finds
- Independent