Once the researchers discovered the French eggs were, in fact, from dinosaurs, more and more started to pop up as other researchers went back to them and started studying them again. It led to lots of questions about the creatures that had laid – and inhabited – the eggs.
A few of the fossils that have popped up are empty – they successfully hatched, and lived out their lives away from their eggs. A few, however, told a different story, one that had life cut short before they could breathe their first breath. In rare cases, the creatures inside are perfectly preserved.
Paleontology got its start as a science beginning in the mid-19th century when researchers in Britain found dinosaur bones for the first time. Plenty of bones had been found before – remember the stories? – but either there were no records or the records were lost.
Experts theorized that the creatures reproduced similarly to modern-day reptiles, but it wasn't until the year 1859 when the first fossilized dinosaur eggs were found. They allowed researchers to study the life cycle in greater detail.
The first fossilized dino eggs appeared in France and were at first thought to have belonged to an unknown species of birds (that's a little bit of foreshadowing). This led to them being overlooked for a long time, but sixty-four years later researchers took another look and correctly re-categorized them as dinosaur eggs.
This leads us back to the American Museum of Natural History, which provided the researchers that did the work in Mongolia. Thanks to this refocused study, our knowledge about dinosaurs, eggs, and plenty of other things have grown by leaps and bounds.
We have no way of studying an on-going life cycle of dinosaurs, which means it's impossible to see how the creatures grew as time went on.
Thanks to fossils, we have snapshots of growth and development, but that's like looking at pictures of a baby, and teenager, and an adult, and knowing everything about the person's life – growth doesn't work that way. But, experts can at least theorize, which led them to believe the incubation process for dinosaurs was similar to today's birds.
Until, however, David J. Varricchio from Montana State University published a paper in 2013 putting forth a different theory. Thanks to his study he's found that certain dinosaur eggs had lots of pores, which suggests they had been covered up underground – before they were scheduled to hatch.
If you've ever seen videos of baby turtles pulling themselves out of the sand and crawling toward the water, you've seen a similar process. This, in turn, suggests that the incubation process does have more in common with modern-day reptiles than birds.