The above is a dinosaur embryo belonging to a species called Massospondylus carinatus which is believed to be an ancestor of the giant sauropods. It (the embryo) was discovered in 1978 and just recently exposed by scientists. Apparently, according to this article enough were discovered that they could work out growth rates and changes in bodily proportions, surprisingly:
That growth pattern turned out to be highly unusual. The hatchling had a huge head and forelimbs as long as its hind legs. As the animal grew, its neck stretched dramatically, while its head got increasingly smaller relative to its body. Its hind legs grew more than twice as long as its forelimbs.
An adult Massospondylus had a head that was only 8 inches (20 centimeters) long. Its upper limbs were only half the size of its thighbones. It grew to be about 16 feet (5 meters) long, with a beanstalk-like neck and an 8-foot (2.4-meter) tail.
The earliest sauropods may have also developed with quadrupedal proportions, like their Massospondylus cousins. But these early sauropods retained their four-footed stance into adulthood.
The growth pattern of the Massospondylus could therefore provide clues about how the giant sauropods evolved.
"These animals are essentially predecessors to those large sauropods," Reisz said.
