When analyzing the two types of eggs he had access to, Erickson discovered some interesting facts. The team discovered that the smaller Hypacrosaurus would have taken somewhere around three months to hatch, while the larger Protoceratops probably would have spent twice that — six months — developing before hatching.
This study is the first time that researchers have been able to pinpoint with any degree of specificity the incubation periods for non-avian dinosaurs. But that’s not even everything Erickson and his team discovered.
Thanks to the study and the research they were doing, Erickson and his team were able to bring about solid evidence that suggests how long Hypacrosaurus and Protoceratops, and dinosaurs like them, took to hatch.
Erickson himself has said that it's the first time such evidence has been found, and it's a huge leap forward in what we know about the development and growth of certain breeds of dinosaurs. But what exactly did we learn from this study?
The team was able to calculate the amount of time during the incubation period the dinosaur spends developing teeth: close to forty percent.
The team was also able to surmise the fact that the dinosaurs took a long time to hatch – Erickson's team estimates these dino eggs incubated for around double the time compared to avian eggs of the same size. But Erickson knew there was more information to find, so he looked at the two types of embryos individually.
While Hypacrosaurus had been a large dinosaur, it was by no means the biggest of them. Modern reptiles and birds tell us that larger eggs – and these larger animals – have longer incubation times and take longer to hatch.
Thus, it's likely that the Hypacrosaurus eggs had plenty of time to go before they were ready to step out into the world. Erickson, in fact, believes that the incubation periods for these eggs could have stretched up to a full twelve months.
Speaking again to The Washington Post, Erickson has said: “It's really surprising. I don't think that people would have entertained the idea that they would have incubated over the better part of a year.”
However, for David J. Varricchio from Montana State University – who always maintained that dinosaur reproduction was closer to modern reptiles than that of modern birds – the news didn't come as much of a shock. According to Varricchio, modern-day reptiles will often spend many months developing in eggs before hatching.