Washington: After sitting in collections for nearly three decades, some well preserved dinosaur eggs have offered new insights into the infancy and growth of early dinosaurs.
They represent the oldest embryos of any land-dwelling vertebrate ever found.
The eggs, found in 1976 in South Africa, date from the early part of the Jurassic Period, 190 million years ago.
They belong to Massospondylus, a member of a group of dinosaurs known as prosauropods that are the ancestors to the later sauropods-the large, four-legged dinosaurs with long necks, typified by the popular ``Brontosaurus`` and Diplodocus.
Robert Reisz of the University of Toronto and his colleagues worked on these fossils, and it was only through modern preparation techniques that these findings were brought to light.
These eggs contain the oldest known embryos of dinosaurs. In fact, they are the oldest of any land-dwelling backboned animal.
The preservation of the embryos is exquisite, permitting a complete reconstruction of the skeleton and detailed interpretations of the anatomy.
The level of ossification - how much of the skeleton has turned to bone - revealed that the embryos were close to hatching. The fossils also reveal that the future hatchlings would have been oddly proportioned and would have looked very different from the adults of the species.
In at least one way, Massospondylus development resembles that of humans; infancy is awkward, and a more erect stance and evenly proportioned body only come later.
There may be another way that Massospondylus infancy was similar to that of humans. The embryos lack teeth and this, combined with the awkward body proportions, suggests that the hatchlings may have required parental care.
If true, these fossils also document the oldest record of parental care.
"This project opens an exciting window into the early history and evolution of dinosaurs.
"Prosauropods are the first dinosaurs to diversify extensively, and they quickly became the most widely spread group, so their biology is particularly interesting as they represent in many ways the dawn of the age of dinosaurs," said Reisz.
The article appeared in the Journal of Vertebrate Palaeontology.