Millions of years before humans appeared on the scene – and long before the asteroid that would wipe out the dinosaurs and pave the way for Homo Erectus – a Protoceratops laid a clutch of eggs in what would later become the Gobi desert in Mongolia.
The eggs never hatched. Instead, they stayed frozen and eventually turned into a group of fossils that survived all the way to our current time. In 2017, scientists at the American Museum of Natural History in New York used a new approach to investigate the fossilized eggs closer, and what they found has sent a shock through the world of dinosaur study.
We know plenty about dinosaurs, and though our knowledge has gaps, there's one area that has remained a mystery until now. Gregory Erickson, a biology professor from Florida State University, has said “virtually nothing is known” about “some of the greatest riddles about dinosaurs.”
Erickson ended up leading a research team in an attempt to solve some of these mysteries, using these fossilized eggs and the new approach to looking at them. They did indeed discover much, as far as paleontology goes, and now our understanding of dinos has grown.
Erickson and his team took the fossilized eggs and inspected the embryos preserved inside, and other fossilized embryos of different dinosaur species. Thanks to advancing technology, they were able to come to some fascinating conclusions about how dinosaurs lived, grew, and reproduced.
To their surprise, their discoveries could also help us learn more about the big extinction events that changed the world and nature enough to wipe dinosaurs off the planet more than once.
Dinosaur fossils have always been an intense field of study, ever since paleontology really got started as a science. We got Greek myths such as the Cyclops from them, Medieval tales about dragons and other huge beasts, and plenty of incredible media thanks to these amazing discoveries.
As science and technology improve, we're able to learn more and more about these remains. A lot of people think that we're able to learn the most from full-formed and fully-grown specimens, preserved in rock, but there are lots of other ways to learn more about these incredible beasts.
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.
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.
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.
It's practically impossible to come to any definite conclusions, but a great deal of this area of paleontology remained a mystery to researchers even after Varricchio's contribution.
Despite all the technology, different fossils, and different minds working to uncover the mysteries, nothing definitive came to light. FSU professor Erickson gave a statement in 2017 to the university summarizing: “Did [dinosaur] eggs incubate slowly like their reptilian cousins, crocodilians and lizards? Or rapidly like living dinosaurs, the birds?”
Erickson hoped to answer the question once and for all, and he decided to throw caution and convention to the wind in his methods.
Erickson knew that reptiles, just like humans, produce a substance known as dentin on a daily basis. Dentin is found in teeth, and it's a tissue that mineralizes up in layers over time, forming a tough core and keeping teeth strong and secure.
Since taking a course in vertebrate paleontology, Erickson was destined to find his way to dinosaurs. He earned the second-highest grade out of five hundred students, and his professor invited him on a field expedition in Montana to collect dinosaurs for the university museum.
The professor became impressed with Erickson's ability to visualize fossils as living animals and encouraged him to enter paleontology. Erickson says that in many ways, the field found him.
Erickson then went on to the Montana State University in Bozeman to get a graduate degree in biology. During his research, he found daily-forming growth lines in dinosaur teeth, similar to alligators and modern mammals. His work doing so helped him earn the Alfred Sherwood Romer Prize for the best student presentation at the 1991 Society of Vertebrate Paleontology annual meeting.
He then went on to get a doctorate in integrative biology at the University of California, Berkeley, followed by post-doctoral research in biomechanical engineering at Stanford, and ecology and evolutionary biology at Brown University.
Today Erickson is a professor of anatomy and vertebrate paleobiology at Florida State University in Tallahassee. His expertise in paleontology, engineering, anatomy, and zoology has led to him studying teeth and bones.
His research has led to questions about growth rates, feeding ecology, and biomechanics both in extinct and living reptiles. Thanks to his work, he co-discovered the approximate bite force of the fearsome Tyrannosaurus rex: a whopping 3,629 kilograms, which is similar to having three small cars land on you. Ouch.
Erickson has received numerous awards for both his research and his teaching. He's been in more than 135 science documentaries and has even hosted the National Geographic Channel series “Hunter & Hunted”.
The series focuses on human interactions with predatory animals. But perhaps his most incredible achievement has to do with teeth, eggs, and embryos.
Like looking at the rings of a tree to determine events in the tree's life, Erickson and other researchers have determined they are able to inspect the age and information about organisms using the same process.
Just by looking at layers in teeth. Erickson told the Washington Post in 2017: “You can basically just count those up and figure out how long it took dentition to form. Dentition is the arrangement or condition of teeth in a particular species, and it should help determine life cycles.
When Erickson was a kid, he would help his father, a wildlife biologist and regional director for the Alaska Department of Fish and Game, catch bears. Yes, you read that right.
His dad taught him to age them using cementum rings in their teeth. He would also catch salmon, and age them from the otoliths – their ear bones. When he entered the paleontology field, Erickson found out that not much work had been done using bone ages.
He set out to introduce his childhood technique to the world of dinosaurs and started determining the age of dinosaur skeletons. Skeletons like the famous Sue, the Tyrannosaurus Rex at the Field Museum of Chicago.
Using growth lines in the skeleton, he found something nobody had thought possible since T-Rex bones grow hollow as they age. Erickson was able to find some bones with intact growth lines – Sue apparently perished at the age of twenty-eight.
Erickson came to wonder if dinosaur embryos could be studied using a similar method. He started reaching out, and contacted experts at Canada's University of Calgary and the American Museum of Natural History in New York.
He wondered if there was a way to test his theory. Despite how rare fossilized dinosaur embryos are, both institutions decided they were able to assist Erickson in his research.
At the American Museum of Natural History, researchers found the eggs from the Gobi Desert in Mongolia, which according to experts at the time belonged to the species Protoceratops Andrewsi, which is a close relative of the Triceratops.
The Protoceratops Andrewsi doesn't have the three horns so famous among dino fans but did sport the fan of bone and horn that came off the head like a headdress.
At about seven ounces and close to the shape of a potato, the eggs were relatively small and didn't give Erickson a lot to work with. However, a few other specimens gave him plenty of work to do.
These dino egg fossils had been discovered in the Canadian province of Alberta and belonged to the species of dinosaur known as the Hypacrosaurus Stebingeri, which is sort of like a cross between a T-Rex and a duckbill dinosaur. It was a bipedal herbivore and usually grew to about nine meters in length.
The duck-billed Hypacrosaurus laid eggs that weighed almost nine pounds. They have the same proportions as a volleyball.
While they were much bigger and had specimens entirely different from those Erickson had started his study on, he found plenty of exciting material.
Within both sets of eggs, researchers had discovered fossilized embryos. The question remained: could Erickson use a dentin analysis to learn about the ages of these dinosaurs?
Could this teach us about the time it took them to hatch? Leading a team of researchers, Erickson got to work on finding out the answer.
They had a couple of steps to work through. First, Erickson and his team used a computed tomography scan, or a CT scan, to inspect the dentition that had developed in all of the embryos' jaws.
Carefully – very carefully – they removed a number of teeth that had already formed from the fossilized eggs. Under microscopes, they could zoom into the finest details of the specimens that had lasted millions of years to see the information they had been looking for.
In fact, according to Erickson, the lines of dentin on each tooth easily became clear and visible. When he was speaking with the Washington Post, he said: “I knew we were in business.”
Erickson had determined it was possible for the team to determine how long the embryos had been alive. In an FSU statement, Erickson explained: “We could literally count [the dentin] to see how long each dinosaur had been developing.”
Excitement grew around the project as Erickson and his team of researchers got to work.
In the same FSU statement, Erickson's co-author Darla Zelenitsky explained: “Time within the egg is a crucial part of development. But this earliest growth stage is so poorly understood because dinosaur embryos are rare. Embryos might be able to tell us how dinosaurs developed and grew very early on in life and if they are more similar to birds or reptiles in these respects.”
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.
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.
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.
Modern science currently holds that birds are the closest living relatives to ancient dinosaurs, which led plenty of researchers to conclude that dinosaurs and birds had similar incubation and development cycles.
However, thanks to Erickson and his team, it's now being theorized that dinosaurs – of the Mesozoic era, at least – had more in common with reptiles than birds.
The birds with the very longest incubation periods, emperor penguins, take about two months to develop in the eggs. And they're certainly outliers: most bird breeds take between ten and thirty days to bust out of their shells.
Compared to modern-day reptiles, and especially ancient dinosaurs, that might as well be a blink of the eye in incubation terms.
Today's reptiles, on the other hand, tend to have an incubation period that lands between one and two months, which on average places them a lot closer to dinosaurs.
However, there are more details that lead researchers to believe dinosaurs aren't as closely related to reptiles than previously thought. In fact, the very way that modern reptiles interact with their developing eggs is different from how researchers believe dinosaurs acted.
Today's reptiles take the tactic of burying their eggs underground – it protects them from predators, and helps preserve warmth. Some reptiles will also hang around their clutch to add additional protection.
However, most reptiles abandon their eggs, and leave them to develop, hatch, and live without interacting with them again. With the long incubation periods of dinosaurs now clearer, the question arose of whether dinosaurs hung around for the lengthy incubation period, or left them alone.
Varricchio provides detail to us about the answer. There's evidence to suggest that unlike their modern-day cousins, some species of dinosaurs had quite a deal of parental instincts.
Several dinosaur species stayed with their eggs for the entire period of incubation, though it seems these species are usually those whose eggs took less time to hatch and were smaller in size.
Dinosaur parents that hung around would have provided additional protection from hungry predators. But for the eggs who took up to a year to hatch, like the Hypacrosaurus, it would have been quite the burden for dino moms and dads to remain in the same location.
If a predator knows you're always going to be in the same location for a long amount of time, even tiny dino brains might have figured out there are some tasty eggs nearby. Researchers have wondered if long incubation periods helped contribute to the extinction of some species.
The discoveries that Erickson and his team have made have called a number of previous theories into question.
One of the theories is the idea of a migration: Researchers have long suspected that a variety of dinosaur species spent the warm summer months in what are now areas of the arctic, and moved south for the winter to escape the cold, into areas of Canada. But with this incubation information, a migration seems more unlikely.
Due to the time it would have taken some dinosaur eggs to incubate and hatch, it now seems unlikely that a number of dinosaur species would have taken the time to migrate.
There's also the detail that since some eggs took so long to hatch, it would have been critical for dinosaur moms to find the perfect place to lay eggs – it's not like they could have picked them up and moved them. They would have had to find a place they could get back to and protect quickly and easily.
There are more dino-difficulties to recognize when you think about parents hanging out the eggs for so long. By staying in place for months on end, dinosaurs risked starvation, wily predators, and even natural disasters.
They would have been at a big disadvantage being tied to a specific area where they had laid their eggs. Maternal and paternal instincts run deep in lots of creatures, and keeping your children safe might have led some dinos to risk their own lives.
You probably know that around sixty-six million years ago an asteroid struck the earth and threw into chaos the entire world.
Debris filled the atmosphere and lowered temperatures dramatically, changing the ecosystem of the entire earth and turning the planet dark.
The number of changes this led to is practically innumerable. Scientists believe that already seventy-five percent of species living at the time died out due to the changing ecosystems, lack of light, and reduced air.
Those species that did survive probably did it by adapting their reproduction methods: species that were able to reproduce quickly ended up surviving and repopulating the earth. For example, the ancestors of modern-day birds developed shorter incubation periods, which not only made their unsafe egg periods shorter, but also allowed them to repopulate more quickly.
But dinosaurs, with their months-long incubation periods, didn't have much of a chance. Species such as the Hypacrosaurus and even the shorter-incubating Protoceratops would have had a much harder time incubating and repopulating.
In an FSU statement, Erickson said: “Our findings might have implications for understanding why dinosaurs went extinct at the end of the Cretaceous period. Whereas amphibians, birds, mammals, and other reptiles made it through and prospered.”
Erickson and his team think that dinosaurs' long incubation and development times stood in the way of their continued survival, but there are likely many other factors at play.
These creatures were often large and required a lot of food to keep themselves going. They had even more disadvantages. Since they needed so much food, and so much of the planet was dying out, many likely succumbed to starvation. In addition, all dinosaurs were cold-blooded, which meant they relied on outside heat sources. With the sun covered under layers of dust and debris, freezing became a much worse threat.
Erickson has also said that dinosaurs likely took a long time to mature, even after they'd hatched. Such slow-developing creatures weren't well-equipped to take on the challenges of the post-asteroid world, and couldn't adapt in time to last.
Adjusting to change and adapting is a critical skill for all species (even humans!) and being unable to do that after such a dramatic change to the planet may have spelled the death of dinosaurs as we know them.
“The dinosaurs found themselves holding some bad cards,” Erickson told The New York Times in 2017. “They had a dead man's hand.”
Dinosaurs like the Hypacrosaurus and the Protoceratops disappeared long after the mass extinction happened, but they are being researched until this very day.
There are still tons of questions researchers aren't able to figure out about dinosaurs, even with Erickson's new methods. For instance, it's impossible to determine the sex of dinosaurs just from looking at their skeletons.
There have been plenty of theories, but they just haven't panned out. Erickson himself has done plenty of studies with what a lot of people consider to be living dinosaurs – alligators – that have resulted in theories being proven incorrect. “That's one of the biggest mysteries – not knowing the sex of an animal.”
Another big question is – how did dinosaurs get so big? Even compared to larger creatures that are around now, such as elephants or giraffes, dinosaurs were huge – even the herbivores. Plenty of them would tower over humans and most other animals.
Even the largest species of animal we have today – the blue whale – only just reaches the size of some of the larger dinosaurs, and the blue whale has the benefit of being an underwater creature, something that facilitates bigger sizes.
One of the most important questions to this day is why dinosaurs aren't around anymore. We have plenty of information about possible reasons, but right now it's little more than a jumbled mass of intersecting theories, ideas, and thoughts.
In an interview for Earth magazine, Erickson has said: “I've spent my career trying to figure out anything I can learn from bones and teeth, and what they can tell you about biology. I always try to find something in a modern animal that I can use in paleontology, like the replacement rates for teeth or how they grew from growth lines in their bones.”
“It's like forensic science: We are very limited by what material is in front of us. Many questions are intractable given what we have to work with.”
Erickson is still working hard to discover more about one of the most exciting species that have walked the earth, and with technology and methods always advancing, researchers are always learning more and more.
Erickson is currently the co-director of the Arctic Paleontological Research Consortium, alongside Pat Druckenmiller, a curator of Alaska's Museum of the North in Fairbanks, and they look at how dinosaurs would have survived in high latitudes.
While it was warmer millions of years ago, there was still plenty of darkness and snow. Alaskan dinosaur fossils are often found preserved in permafrost, and while the work is difficult, Erickson and Druckenmiller are getting results.
“Almost every dinosaur [we find] is a new species. We put out a theory a few years ago that the Arctic dinosaurs were a cold-adapted group and that's why they are all different from other parts of the continent.”
The lack of ectotherms – animals that are dependent on external sources of body heat – like turtles or crocodiles supports the idea of a division of dinosaurs who developed into being warm-blooded when previously all research led to dinos being entirely cold-blooded.
Erickson has even discovered an entirely new species of dinosaur that lived approximately eighty-five million years ago. In 2008, members of the Birmingham Paleontology Society discovered a complete skull, dozens of backbones, a partial hip bone, and several bones from the limbs.
Erickson ended up studying the bones alongside a few others, and they quickly determined that the bones belonged to an undiscovered dinosaur – a huge advancement in paleontology.
The team was led to believe it was one of the most complete duck-billed dinosaur skeletons ever to be found in the eastern United States. Its teeth show an ability to grind plants similar to cows or horses and are similar to early hadrosaurids, and it allowed them to chew and digest a wide variety of plants.
In an interview with the Tallahassee Democrat, Erickson said: “These dinosaurs eventually became the dominant plant-eaters around the world.”
“It has an excellent skeleton and it has a skull. It is the only primitive hadrosaurid found with a whole skull.” The research team named the dinosaur species Eotrachodon Orientalis.
A rough translation is “dawn rough tooth from the east.” The first duck-billed dinosaur was discovered in 1856 and was named “Trachodon” – a name that Eotrachodon plays homage to.
The late Cretaceous Period, roughly 85 million years ago, had incredible differences as far as our landmasses were concerned. North America had a huge, one thousand mile sea dividing it into two halves, connecting the Gulf of Mexico to the Arctic Ocean, stretching from Georgia and Alabama all the way north into Canada.
This created two landmasses, known as Laramidia to the west and Appalachia to the east. This skeleton suggests that dinosaurs of this species originated in Appalachia and then went on to disperse via land-bridges into other areas of the Americas.
This discovery also sheds light on the history of dinosaurs and where their remains are more likely to be found. There are areas in Wyoming, Montana, Alberta (in Canada), China, and Africa.
Erickson said with a laugh: “People don't realize there were southern dinosaurs.” There are about a thousand species of dinosaurs, and about forty are identified as “duck-billed.”
Erickson is only one of around three-hundred and fifty professional dinosaur paleontologists working in the world, so there is plenty of work still to be done. “You are most likely to make it into Major League Baseball than do what I do,” Erickson said.
Because of this, most dinosaur remains are found by the public, or by paleontology societies such as the Birmingham chapter that found the duck-billed dinosaur. There are plenty of stories that tell us about kids playing in the woods or near a lake and discovering a set of fossilized bones (much to their utter delight).
This is why, as Erickson says, it's so critical for experts to be notified. Plenty of these fossils are already damaged by time, the weight of the world, and movements in landmasses. If amateurs try to transport or study them, more damage could be one slip away.
“It's a very delicate task to get a dinosaur out [of the ground] and get it properly prepared.” More damage means it's more trouble studying the bones and fossils. The easiest remains to study are fully-formed skeletons, but as we've seen, even the smallest dino eggs can yield information.
Dinosaur study is a slow science. Just like the movement of landmasses or the immense movements of huge creatures, there is advancement, but it can sometimes be hard to see.
Many years can be spent aligning a few bones, but every once in a while there are big leaps forward – as far as paleontology works, at least. Erickson and his fellow researchers are always working to discover the next big thing.
Millions of years after the asteroid-assisted mass extinction, creatures like the Hypacrosaurus and Protoceratops have been gone for a long time, but their fossilized bones and eggs remain, and allow us plenty of ways to learn more about these huge, incredible creatures.
What other answers await us, hidden deep inside caves, or buried under the ground? Plenty of information about dinosaurs, the history of the earth, and how our modern-day animals relate to those long-lost beasts.