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Dinosaur Egg Fossils- 23 Things To Know About Them

Over the last few years, some amazing discoveries about dinosaur egg fossils have helped scientists solve a few mysteries about dinosaurs. Some theories have been confirmed, while others have changed. Here are 23 things to know about those amazing dinosaur eggs.

Dinosaur eggs are trace fossils and they help paleontologists understand more about the behavior and how the dinosaur lived – AdventureDinosaurs

Paleontology, a science that delves into the life of prehistoric organisms, brings forth snapshots of dinosaur species, including the carnivorous Oviraptor and herbivorous Protoceratops, inhabitants of the Mesozoic Era. Discoveries of dinosaur egg fossils, nestled within the geological layers of notable locations like the Gobi Desert, provide these snapshots.

These dinosaur eggs, each encased in a protective shell, are repositories of critical information about prehistoric reproduction practices. The fossilization process, abetted by specific environmental conditions, has impeccably preserved both the shell and the embryos within these eggs, revealing the initial phases of dinosaur development.

Herbivorous dinosaur Maiasaura, a Hadrosaurid species, is distinct for its nurturing instinct, evidenced by its well-preserved nests found in sediment strata. Carnivorous Oviraptor, initially misunderstood as an egg thief, is now recognized for its brooding behavior.

Beyond illuminating the life history of individual dinosaur species, these egg fossils offer a broader perspective on the prehistoric ecosystem. They offer insights into overarching phenomena such as the extinction event that concluded the reign of the dinosaurs. Therefore, the study of dinosaur egg fossils is like unravelling historiographic material, each contributing to a deeper understanding of the dinosaur lifestyle and their environmental conditions during the prehistoric times.

#1 Are There Real Dinosaur Eggs?

Yes, there are real dinosaur egg fossils. Paleontologists have found fossilized dinosaur eggs all over the world, even on Antarctica. Dinosaur eggs have been found individually, together in a nest, and some have even been found containing fossilized embryos.

Dinosaur eggs come in different sizes and shapes, the most common non-scientific descriptions being elongated and round. 

Not all eggs can be identified as belonging to a specific dinosaur species, although similarities in shape and size help identification. 

Scientists have created a systematic way of classifying dinosaur eggs which came into limited use in the 1970s called Parataxonomy and uses the traditional Linnaean system. 

Oogenera is the genera given to eggshell types. It classifies eggs based on the structure and physical characteristics of the eggs instead of the dinosaur species, which often are not known. (Source), (Source).

#2 What Are The Types Of Dinosaur Eggs?

There are elongated and oval-shaped eggs that are pear-shaped or symmetrical. There are also round dinosaur eggs. The scientific terms for types of dinosaur eggs are Ovaloid (or Ovoid), Pyriform and Spherical. They can be surprisingly diverse in shape. 

Oval-Shaped Dinosaur Eggs

These dinosaur eggs are shaped like a football. They are the most common type of egg and come in two varieties: elongated oval eggs with pointed ends or spherical-shaped ovaloid (or ovoid) dinosaur shells. 

Dinosaurs that lay oval-shaped eggs include hadrosaurs such as Edmontosaurus.

The shape of these dinosaur eggs is more elongated and narrow but still looks oval-shaped.

Pyriform Dinosaur Eggs

Pyriform eggs are shaped like an onion or pear, with the top half sliced off. Typical dinosaurs that laid pyriform eggs are theropods such as Troodon and Citipati. Their eggs were shaped like a pear with a narrow top and a wide, round bottom. (Source

Spherical Dinosaur Eggs

These dinosaur eggs are shaped like a ball and have been attributed to dinosaurs such as sauropods. Paleontologists have found spherical eggs in the fossil record of titanosaur sauropods and other herbivorous dinosaurs. The eggs of titanosaur sauropods are some of the largest fossilized eggs ever found.

#3 What Type of Fossil Is A Dinosaur Egg?

In general, a dinosaur egg is considered to be a “trace fossil.” It is a trace from a dinosaur, but not actually a part or actual remains of the dinosaur that died. 

Fossilized dinosaur eggs tell us about the reproduction, breeding, and embryos of dinosaurs. Other things that are considered trace fossils are coprolite (dinosaur dung) and footprints. 

Dinosaur trace fossils are an important part of the paleontological study, and they help us understand the life and death of dinosaurs. The left-behind fossils in sedimentary rocks can tell us about dinosaur hunting behavior, locomotion, and interactions with other animals. Trace fossils add to this understanding.

#4 How Much is a Fossilized Dinosaur Egg Worth?

On average, a dinosaur egg is worth about $500 to $2000 in 2021. 

Some of the things that influence how much a fossilized dinosaur egg would be range from whether the egg is from a nest or singular and whether it has a fossilized embryo. I wrote a whole article just on this topic. Check out my article –How Much Would A Real Dinosaur Egg Be Worth in 2021?

#5 How Big Were Dinosaur Eggs?

On average, a dinosaur egg can reach sizes of 13 inches in length and 9 inches in diameter for elongated dinosaur eggs and 12 inches or more in diameter for spherical dinosaur eggs. For oval-shaped dinosaur eggs, they vary in width and diameter depending on the shape. 

The size of dinosaur eggs can vary depending on the type and species. For example, an average egg for a duck-billed hadrosaur is about 10 inches in diameter.

Sauropod dinosaur eggs, which were spherical in shape, ranged from about 18 inches in diameter to more than two feet. The titanosaur sauropod eggs found in France and Argentina ranged from about 18 inches to 24 inches in diameter. (Source)

Elongated dinosaur eggs were long and thin and ranged from about 12 inches to more than 18. 

Various oviraptorid egg species lived in China (including oviraptorid species endemic to China. A few found primarily outside of China), which usually lay eggs of greater than six inches in length within four to five inches in width.

#6 How Do You Know If A Dinosaur Egg Is Real?

Determining whether an egg-looking rock is really a dinosaur egg is complicated and depends on many factors. I often get asked how do you know if a specimen is a real dinosaur egg. Here are a few tips to get you on the right track:

1. Where was the specimen found, and have there been any dinosaur fossils found in that area before?
2. Dinosaur bones and trace fossils only fossilize under specific conditions or if the right sand and minerals covered the dinosaur egg. 
Check with a university or museum geologist if sandstone deposits or other mineral layers are in the area where you found your fossil specimen. 
3. Contact a paleontologist or a university’s paleontology department and ask them
4. Also, consider the fossil specimen – what is the shape, the structure (do the cracks look like a fossilized egg), was it found with other eggs? 

#7 What Is The Largest Dinosaur Egg Ever Found?

The largest dinosaur egg ever found that is spherical in shape was 24 inches and the largest elongated dinosaur egg was 17.72 inches long. The largest soft-shelled dinosaur egg was 11 inches. 

You have likely heard of the largest dinosaur ever, the Argentinosaurus. The T-Rex is one of the most famous dinosaurs. But what about the largest egg?

The largest Spherical dinosaur eggs come from France. Some of the largest measure 24 inches in diameter and were found in 1846. 

Although it wasn’t identified initially as a dinosaur egg (dinosaurs had not been named or classified), scientists later realized that it was a sauropod egg. 

Paleontologists believe the sauropod that laid the giant egg was a titanosaur sauropod known as Hypselosaurus, although this dinosaur’s classification is in doubt.

In 1995, the discovery of large elongated eggs in Heyuan in China was exciting enough, but what was even more exciting was the discovery of Baby Louie. 

Not only were these the largest elongated eggs ever found, but they also held a fully fossilized embryo inside them. Although other fossilized embryos have been found, none have been this big. Scientists believe the egg was laid by an oviraptorid. (Source

A soft-shell dinosaur egg, considered the largest ever found, was discovered in Antarctica in 2020 and is thought by paleontologists to be about 50 million years old and probably was laid by a large marine reptile. The size was 11 inches long. (Source

#8 Were Dinosaur Eggs Soft Or Hard?

In general, dinosaur eggs are hard-shelled based on the many thousands of dinosaur egg fossils that have been found all over the world. 

Paleontologists suggest that some dinosaur eggs could have been soft-shelled, which might explain why some dinosaur eggs (like carnivores such as Allosaurus) have not yet been found.

Soft-shelled eggs are not often found, and it could be because of the fossilization process, which makes it more difficult for softer eggs to survive that process.

Interestingly, the fossilized soft-shell egg of a marine reptile that lived during the Mesozoic was found in 2020 in Antarctica. 

#9 What Is The Smallest Dinosaur Egg?

The smallest dinosaur egg is 1.77 inches long and 0.79 inches in diameter and belonged to a non-avian dinosaur. It was found in Japan and was publicly recognized by Guinness World Records. 

Scientists suggest that the dinosaur egg dated back to the Cretaceous period 110 million years ago. (Source

#10 How Large Were T. Rex Eggs?

T. Rex eggs were about 17 inches long. 3D scans of embryos found in Montana in 1987 have scientists excited have positively identified T. Rex embryos, an amazing find and the first of its kind. 

Based on the size of the T. Rex embryos, it is estimated that the eggs had a length of about 17 inches. (Source

#11 How To Find A Dinosaur Egg?

Finding dinosaur eggs is not an easy undertaking. Even with expert help, there is no guarantee, and it could take a long time. Here are a few ideas to help you find those elusive dinosaur eggs if you are determined to find dinosaur eggs:

1) Identify places where fossils have been found before. Known geological formations that support dinosaur fossils can be found on some geology websites and museum pages. 

2) Talk with a geologist, paleontologist, or paleontologist about whether sandstone deposits are in the area where you are thinking of looking for dinosaur eggs. Eggs fossilize if the right type of mineral deposits buried the eggs. 

Understanding the fossilization process will help you avoid places where there cannot be fossils and choose the ones that can. Read about the process here – Learn How Dinosaur Eggs Are Fossilized And Identified

3) Many fossil discoveries have been found on construction sites when bulldozers dig up the land. If construction is being done in places where other dinosaur fossils have been found and a geologist or paleontologist agree, it might be a place to find dinosaur eggs. Be sure to ask for permission (in writing) if you can search the construction site. 

#12 Where Are Dinosaur Eggs Found?

Dinosaur eggs are found all over the world and have been found on all continents. A variety of environments were favorable for dinosaur egg fossilization, such as floodplains, sandy beaches, and ancient sand dunes.

Some of the most spectacular finds are:

Antarctica – Soft-shelled egg from a marine reptile
Argentina – Thousands of titanosaur sauropod dinosaur eggs
Canada – Hypacrsaurus (crested hadrosaur) eggs
China – Thousands of dinosaur eggs have been found of oviraptors as well as flying reptiles such as Pterosaurs
France – Thousands of sauropod dinosaur eggs have been found
Mongolia – Oviraptorid dinosaur eggs in nests, as well as fossilized embryos, have been found
Spain – Thousands found in nesting grounds. Sauropod dinosaur eggs but also other species of dinosaur
United States – Hundreds of Maiasaur (hadrosaur) dinosaur eggs in nests have been found

#13 How Many Dinosaur Eggs Have Been Found?

More than 500,000 fossilized eggs have been found in over 200 dinosaur sites around the world. Paleontologists believe most of these are dinosaur eggs. It’s important to note that these sites may have found marine reptiles, flying reptiles, ancient turtles, and crocodiles because they are similar in size and shape, and dinosaur fossils were not always found right next to the eggs.

#14 Are Dinosaur Eggs Found In China?

Yes, dinosaur eggs have been found in China. In fact, thousands of Oviraptor dinosaur eggs have been found in Henan Province.

In addition to dinosaur eggs (such as Oviraptor), fossilized flying reptile eggs like Pterosaurs have been found in China and marine reptiles and turtles. Marine reptiles are known to lay eggs similar to present-day relatives like crocodiles and turtles.

In some cases, there is no clear evidence as to whether or not they are actually eggs from dinosaurs because the fossilized eggshells have been found in a layer of mudstone that has also yielded fossils like turtles and crocodiles, which could lead one into thinking these were just reptile nests rather than dinosaur nesting grounds.

You can read more about the amazing dinosaurs found in China here – Dinosaur Fossils Found In China – The Key Groups of Chinese Dinosaurs

#15 What Type of Dinosaur Laid Eggs?

Paleontologists suggest that all dinosaurs laid eggs. Fossil remains of dinosaur eggs have linked them to certain dinosaurs, yet not every species have been proven to lay eggs. 

However, in terms of classification, dinosaurs evolved from ancient reptiles that also laid eggs (Sauropsida), including modern-day reptiles and birds.

A few of the dinosaurs that are known to lay eggs because of the fossil bones found near the dinosaur eggs are:

*Oviraptorids – multiple egg clutches

#16 What Color Were Dinosaur Eggs?

Dinosaur eggs that have been found are blue-green, brown, and reddish-brown in color. Scientists have found pigments in the fossilized eggs of blue, green, and red. 

Looking deeper into the question of the color of dinosaur eggs, Oviraptor eggs have been found in Mongolia and China, and the color of these eggs is brownish or green in color with some spots on them.

In contrast, there are similar dinosaur eggs that have lost some of their colors during fossilization. The color can range from dark brown to light brown; however, the color does not seem to be preserved because of colorization by soil and minerals during fossilization.

#17 What Dinosaur Laid the Biggest Eggs?

The biggest elongated (oval-shaped) dinosaur egg was laid by an Oviraptorid (Lufengosaurus) measuring 18 inches long and 6 inches wide. A titanosaur sauropod laid the biggest spherical or round-shaped dinosaur egg in France that measures 24 inches in diameter. 

Initially, the dinosaur was named a Hypselosaurus. However, some scientists think it may be a related species of titanosaur sauropod.

#18 Did All Dinosaurs Hatch From Eggs?

Paleontologists have discovered fossilized eggs and even eggs with dinosaur embryos intact, which prove dinosaurs could hatch from eggs. However, no one can say whether every species of dinosaurs hatched from eggs. 

Some marine reptiles from the Mesozoic era had live births. Still, research suggests that most theropod dinosaurs laid eggs, including T. Rex and Allosaurus, thought to be apex predators.

I wrote a whole article just on this subject, and you can check it out here: Do All Dinosaurs Hatch From Eggs?- What We Know About Dino Eggs.

Related Dinosaur Articles You Might Also Be Interested In:
Can You Buy and Own a Dinosaur Bone? The Law vs the Science
How Much Would A Real Dinosaur Egg Be Worth
Learn How Dinosaur Eggs Are Fossilized And Identified

#19 Did Dinosaurs Lay Eggs In Nests?

In general, the dinosaurs known to have laid eggs in nests are Oviraptorids (in China and Mongolia) and Hadrosaurs in North America. Many other nests of dinosaur eggs have been found in nesting sites, but the type of dinosaur that laid the eggs is not always clear.

What is interesting is that scientists are only now discovering whether dinosaurs laid these nests in open nests and then sat on them (like modern birds) or buried in soil and vegetation as reptiles do. 

An in-depth study summarized by LiveScience suggests that there is a correlation to the thickness and porosity (being full of tiny holes that water or air can get through) of eggshells and whether the eggs were covered or incubated by the mother dinosaur. 

Most dinosaurs, including the long-necked sauropods, theropods, and maybe plant-eating ornithischians, buried their eggs in nests, the researchers found. 

In contrast, theropods with a higher degree of development laid eggs with little porosity and most likely hatched them in open nests.

#20 What Are Dinosaur Eggs In A Nest Called?

Dinosaur eggs that are grouped in a nest are called a clutch. Multiple clutches of dinosaur eggs have been found in the United States, China, Mongolia, Spain, and Argentina, to name a few.

#21 Did Dinosaurs Sit On Their Eggs?

After the 2020 discovery of a non-avian theropod dinosaur fossil, in which the dinosaur skeleton was sitting on top of the clutch of eggs, it confirms that, yes, some dinosaur species do sit on their eggs.

Until this fossil discovery in Yunnan, China, scientists have suggested that dinosaurs would sit on their eggs based on the multiple clutches found worldwide. But the Yunnan find confirms it is true. 

The Oviraptosaur and clutch fossils yielded a full set of blue-green eggs and even fossilized embryos, in addition to the skeleton. (Source

#22 Are There Fossilized Dinosaur Embryos?

Fossilized dinosaur embryos have been discovered and even re-discovered with the help of scientific advancements and using technology like x-rays, 3D scans, CT scans which allow scientists to penetrate the layers of minerals and form a picture of the insides of the fossilized eggs.

In the mid-1990s, the first fossilized embryo discovered was a Lufengosaurus embryo, named “Baby Louie” by scientists and the press. It measured about two inches long and contained bones of the upper arm, hand, pelvis, and hind legs. 

Since then, many more embryos have been found by re-examining dinosaur eggs found decades before with modern technology. Dinosaur embryos have also been found in Mongolia, North America, and South America. 

If you are interested in reading more about tools that paleontologists use, check out my article- Where Do Paleontologists Work? This Is What Surprising Tools They Use.

#23 Why Are Fossilized Dinosaur Eggs Found Unhatched?

There are several reasons why fossilized dinosaur eggs are found unhatched, and most of them are linked to the fossilization process. In many cases, scientists suggest that the eggs were suddenly covered by sand and dirt, which led to the mineralization of the dinosaur eggs and other fossils. 

Other cases have to do with an unexpected change in the environment, like flash floods or geologic events like earthquakes and erupting volcanoes. These events would stop the incubation of the eggs and start the fossilization process.

I wrote an article about the fossilization process and you can read it here- Learn How Dinosaur Eggs Are Fossilized And Identified.