An amateur paleontologist's chance find in a fossil-rich region of southern China has uncovered one of the oldest and most revealing sets of dinosaur embryos ever discovered.
Researchers working on the find have so far identified the scattered bones of about 20 embryos, all thought to belong to an early species of plant-eating dinosaur called Lufengosaurus that lived near the start of the Jurassic period roughly 200 million years ago.
Significantly, the embryonic bones represent various states of maturity, offering a detailed picture of dinosaur development.
"That's what makes this particularly exciting," said Robert Reisz, a paleontologist at the University of Toronto, Mississauga, and lead author of a study that details the find. "We're looking at different stages of the embryonic life of this animal."
Prof. Reisz said the remains clearly show the dinosaur embryos grew quickly – not a surprising revelation for dinosaurs, but one that suggests that members of this particular branch of the dinosaur family tree were outpacing others in their ability to attain an impressive body size in short order.
The accelerated growth rate likely served as an important survival strategy, Prof. Reisz said. "The faster you grow, the faster you get out of the prey range of predators."
Experts are fascinated by dinosaur growth and how it relates to that of birds, which also mature quickly. "All living birds grow up in a single year," said Dr. John Horner, a paleontologist at Montana State University in Bozeman. For dinosaurs, keeping a bird-like growth rate going over a longer period may have been the secret to reaching their giant size, he added.
The location of the embryos in Yunnan province was discovered by Timothy Huang, a Taiwanese fossil hunter, who contacted Prof. Reisz, who has previously worked on dinosaur embryos found in South Africa. Ten other authors from Australia, China, Germany and Taiwan also worked on the fossils. Their results, published on Thursday in the journal Nature, also reveal the possible presence of organic material in some of the bones. If it can be successfully extracted, such material would yield invaluable molecular clues to early dinosaur evolution.
"It's really nice to have these specimens," said Kevin Padian, a paleontologist at the University of California, Berkeley, who was not involved with the work. Prof. Padian noted that later species of the same branch of dinosaurs, the sauropods, "include the largest beast ever to walk on Earth, and they grew faster than anything else we know on land."
David Henderson, curator of paleontology at the Royal Tyrrell Museum in Drumheller, Alta., added that the embryonic bones might shed light on how sauropods evolved to walk on all fours. "It is widely agreed that the earliest dinosaurs were all bipedal," he said.