Which came first, the chicken or the egg? Maybe the dinosaur egg came first!

There is a legendary "dark cuisine". Some people love it and regard it as a rare delicacy; some people stay away from it and get goose bumps at the first sight of it, not to mention putting it in their mouths to taste it... This terrible food is hairy eggs.

Hairy Egg

Source | Tuchong Creative

Whether hairy eggs are delicious or not is not a topic for the moment, but when it comes to chicks that have not yet been born in eggshells, we have to think of their ancestors, the dinosaurs, in the Mesozoic Era. We know that dinosaurs also hatched from eggs, so do unhatched dinosaurs also have "hairy dinosaur eggs"?

Recently, a team of scientists from China, Britain and Canada published a paper on a "fossil hairy egg" discovered in the Late Cretaceous period in Ganzhou, Jiangxi Province, my country.

"Fossilized eggs" preserved in museums

Source: Reviewer of this article

This is a dinosaur embryo fossil that has not yet hatched. The Yingliang Stone Natural History Museum in Fujian Province, which preserves this fossil, gave this unborn dinosaur fossil a cute nickname - "Yingliang Beibei". So, what is the relationship between the fossilized dinosaur embryo and the legendary dark cooking hairy egg?

1

The structure of an egg

Both birds and dinosaurs reproduce by laying eggs. Let’s first take a look at the structures of a newly laid egg.

Take an egg as an example. The outermost layer is the eggshell, which is mainly composed of calcium carbonate. There are two layers of eggshell membranes (outer shell membrane and inner shell membrane) under the eggshell. At the big end of the egg, there is a large "bubble" sandwiched between the two layers of eggshell membranes, which is the air chamber.

The structure of an egg: 1. Eggshell 2. Outer shell membrane 3. Inner shell membrane 4. Upper frenulum 5. Thin albumen 6. Thick albumen 7. Vitelline membrane 8. Nuclear fascia 9. Germinal disc 10. Dark yolk 11. Light yolk 12. Inner albumen 13. Lower frenulum 14. Air chamber 15. Shell rim

Source | Wikipedia

The semi-fluid gelatinous substance inside the inner shell membrane is protein. The main components of protein are water and protein. It plays the role of shock absorption, moisturizing and protecting the embryo, which is similar to the amniotic fluid of mammals.

The egg white wraps around the yolk, and the ligaments connect the yolk and fix it inside the egg white. There is also a layer of yolk membrane on the surface of the yolk. If you puncture it, you will find that the yellow liquid substance inside flows out.

Children often ask whether it is the egg white or the yolk that eventually turns into a chick. In fact, the main function of the egg yolk is to provide nutrients for the embryo's development. What eventually turns into a chick is the embryonic disc, which is a small dot on the yolk and is difficult to see if you don't pay attention.

2

What is a "hairy egg"?

Fertilized eggs will hatch into chicks in about 21 days under suitable conditions. Hairy eggs, as the name suggests, are eggs with hair, that is, chicken embryos that have grown feathers during the development process.

Hairy eggs, also known as lucky eggs, chicken eggs, chicken eggs, happy eggs, etc., are actually eggs whose development process is suddenly terminated during the incubation process.

Chicken embryo on day 9 of development

Source: Wikipedia

There are many reasons for the termination of development of hairy eggs, including sudden changes in temperature and humidity, infection by bacteria and parasites, and artificial termination of development. Many of the hairy eggs sold on the market today, known as "live pearls", are obtained by artificially terminating embryonic development around the 12th day of egg development and then processing them into food.

3

“Yingliang Beibei” is also a hairy egg?

As we all know, some theropod dinosaurs eventually evolved into birds.

From the fossil morphology, Yingliang Beibei has a short and tall skull and no teeth, indicating that it is an oviraptorosaur. The preservation state of this dinosaur embryo fossil is quite primitive, without much interference from fossilization, and clearly shows its state when it was alive. The total length of this little dinosaur from head to tail is estimated to be 27 cm, curled up in a 17 cm long egg fossil.

The Yingliang Beibei fossil

Source: Reviewer of this article

So far, paleontologists have discovered many Oviraptorosaur fossils, including Oviraptorosaur egg fossils, adult dinosaurs incubating eggs, and Oviraptorosaur embryos about to hatch.

Evolutionary tree of birds (based on a phylogenetic analysis by Godefroit et al., 2013)

The "Oviraptorosaurs" in the picture are Oviraptorosaurs

Source: Wikipedia

Oviraptorosaurs are a group of feathered theropod dinosaurs known from the Cretaceous of Asia and North America. This group of dinosaurs is closely related to birds. Oviraptorosaurs had a wide variety of beak shapes and body shapes. These characteristics probably enabled them to have a wide range of diets, including herbivores, omnivores, and carnivores.

Reconstruction of the Oviraptorosaur

Source: Wikipedia

The Yingliang Beibei fossil is an unhatched Oviraptor embryo inside an eggshell, so it is likely to have soft feathers like a chick. In other words, this unhatched dinosaur embryo fossil came from a "hairy egg" 72 to 66 million years ago.

So, regarding the question of "which came first, the chicken or the egg?", we can boldly say here that "the hairy egg came first".

4

The problem of breaking the shell

Although they are both eggs, dinosaur eggs are obviously much thicker than chicken eggs. How should a mature baby dinosaur break the eggshell and hatch successfully? "Yingliang Beibei" provides us with some answers.

A fully developed bird in an egg will first adjust its body position shortly before hatching. Under central nervous system control, the chick will first bend its body and put its head under its wings, which stabilizes the head and helps it to align its beak with the same point on the shell, making it easier to break the eggshell.

Restoration drawing of "Yingliang Beibei": Forest Guardian Animation

Source: Reviewer of this article

Scientists have also found this posture in the fossils of Yingliang Beibei. In other words, the behavior of birds shrinking their bodies to adjust their posture before hatching is probably not "original", but inherited from their theropod ancestors. This "shell-breaking secret" from their ancestors has long been written into the central nervous system of birds in the long river of evolution.

In addition, this discovery is the first of its kind in dinosaur embryo fossils, and it further confirms the relationship between dinosaurs and birds.

In addition to adjusting its body posture, "Yingliang Beibei" also has a "shell-breaking artifact" inherited from its older ancestors - the egg teeth.

The egg tooth of a turtle (the white pointed protrusion at the front of the snout)

Source: Wikipedia

The egg tooth is a relatively sharp keratin tooth. This special structure for breaking eggshells is found in reptiles, birds, monotremes, and even some amphibians (Eleutherodactylus). During hatching, the egg tooth at the tip of the beak or snout allows the newborn animal to easily pierce the eggshell from the inside to the outside world.

If Yingliang Beibei could successfully hatch, its condition might be closer to the Oviraptorosaur cub fossil Beibeilong sinensis published a few years ago, and we might find it difficult to obtain information about the posture of the dinosaur before hatching from the fossil.

Beibeisaurus sinensis fossil

Source: Wikipedia

Let me digress a little. Many people think that hairy eggs are a nutritious food, and that they have the nutrients of both chicken and eggs, and are not polluted. But in fact, during the development of chicks, after cell differentiation and absorption and utilization of egg yolk substances, many nutrients in the egg yolk have been absorbed by the chicks, and they do not have any special nutritional value. In addition, the hormone level of developing chicken embryos is relatively high, and excessive consumption may have an adverse effect on the development of adolescents.

All in all, hairy eggs can still be tasted as a delicacy, but you should choose products that have been quarantined and have reliable manufacturers. You should be cautious before buying and eating hairy eggs of unknown origin sold at roadside stalls.

Audit expert: Xing Lida

Well-known young paleontologist

Associate Professor, China University of Geosciences (Beijing)

Source: Digital Beijing Science Center