How did dinosaurs mate? – BBC News Korea

Dinosaur mating is a problem that scientists have not been able to find an answer to for a long time. But recently a new idea has emerged. The answer may be found in the unique characteristics of dinosaurs.

I was talking about tyrannosaurus reproductive organs in Jacob Winter’s office. “Someone…” I stuttered in embarrassment. Then, the clearing calmly said, “I’ll have to break through.”

The place we talked to was the University of Bristol, UK. Glade is a scholar who studies fossils. Since the topic was awkward, my eyes kept looking inside the office.

Books, papers, and fossils were mixed on the bookshelf. Ancient insects with vivid wing veins and colors, vampire squids with ink sacs, and ancient insects testify to the lost era. It was like a cross between a museum and a library.

There was also today’s protagonist, Psittacosaurus. Dubbed the “parrot beaked lizard,” this cute little dinosaur lived in what is today Asia between 133 and 120 million years ago. The specimen in front of me was a specimen famous for its vivid stripes and feathers. However, it received more attention because of the fact that the buttocks remained. (More details on this can be found in the middle of this article.)

I went back to our conversation. Winter was talking about a pair of tyrannosaurs from the Ixian Formation in Liaoning Province, China. He was wondering ‘were they copulating?’

With modern science and technology, scientists are rapidly accumulating information about dinosaurs. Many of them are unimaginable decades ago.

For example, through molecular studies, scientists have found red blood cells and collagen in theropods 76 million years ago. This concluded that Triceratops and Stegosaurus were cold-blooded, and the herbivorous Nodosaurus was light reddish-brown. Evidence has also been found that Spinosaurus, famous for its large sails on its back, hunted in deep water with its teeth and strong jaws reaching up to 15 centimeters, iguanodon was surprisingly intelligent, and pterosaurs found food while walking. .

Still, nothing is known about the mating of dinosaurs. To this day, scientists cannot accurately distinguish between dinosaur males and females, let alone the courtship and genitalia of dinosaurs. Unraveling dinosaur biology requires some basic knowledge, but for now, only one thing is certain. Dinosaurs may have also mate.

Winter said that clues to the interpretation of Tyrannosaurus fossils can be found at the Messelpit fossil site in Germany. Fossils of horses the size of foxes, giant ants, and snakes with lizards and worms in the stomachs of snakes were found in the messel pits. They are relatively well preserved. Fossils of freshwater turtles have also been found here, of which about nine pairs seem to have died during mating. The tail-to-tail or fossilized posture is evidence. This is where Winter’s theory plays an important role.

Messel pit is the tomb of prehistoric times. Dating back to the Eocene, between 57 and 36 million years ago, it would have been a crater in a dense subtropical rain forest. No one knows how the burial of animals and plants took place here. One hypothesis is that the crater periodically emitted clouds of carbon dioxide. The poor tortoises met such a situation and fell to the floor, and their lust was locked in the mud for thousands of years.

However, the posture of the tortoise that became a fossil was unusual. Usually, turtles mate with one on top of the other, and these tortoises were facing each other.

Glade, noticing my embarrassment, said that after the tortoise died, it would have drifted with its genitals attached. It was connected through the male genitalia.

When this point is applied to Tyrannosaurus fossils, similarities are seen. “These dinosaurs are overlapping their tails towards each other,” says Glade. “I think they became fossils during mating.”

There are no other cases yet. Winter also admitted that his theory was based on speculation and that it was an unpublished hypothesis. But if animals were fossilized while hugging each other, it could give us clues about some hitherto undiscovered body organ. Yes. Perhaps male Tyrannosaurus, including T. rex, had penises.

There are more obvious examples of dinosaur mating. It is a fossil Psittacosaurus that has received worldwide attention.

Winter showed me his collection and told me a story like a novel.

Zehol biome in northeastern China during the Early Cretaceous. One sunny day here, a little Psittacosaurus went to the lake to drink. This dinosaur was almost all large, so the body length was only about 91 cm.

Psittacosaurus slowly approached the water using only two legs. (This dinosaur only walked on four legs when it was young.) Then suddenly tragedy struck. He slipped and drowned while leaning down to drink water through his parrot-like mouth. The dinosaur that sank to the bottom of the lake died with its buttocks exposed, and the buttocks became the starting point for future human reproductive research.

Glade pointed to a dark, round piece of skin just below the tail on the remaining rump. It is claimed that this is the preserved dinosaur genitalia that survived the difficult times of the early Cretaceous.

In fact, the Psittacosaurus in the Glade’s office is not an actual fossil. This is a real-size model. However, even the stripes found in the fossils were reflected as accurately and precisely as possible.

So, what does this dinosaur’s hindquarters tell us?

First, like birds and crocodiles, which are their relatives, dinosaurs also had cloaca. The cloaca is readily seen in all terrestrial vertebrates except mammals. One opening through which excretion, urine, copulation, and childbirth takes place is the cloaca. So far, there has been no evidence that dinosaurs are anatomically identical to their evolutionary cousins.

“If you look here (he points under the tail of Psittacosaurus towards the cloaca), you see a lot of pigment,” says Glader. He explained that this is melanin and that this specimen was left behind because of a very special preservation.

We usually think of melanin as the compound that gives the skin its dark color. However, melanin plays a very diverse role in the natural world, from the pigment in squid ink to the back of the human eye. It is also a strong antibacterial agent and is found in many livers in amphibians and reptiles.

“Insects use melanin as an immune system to protect them from infection,” Winter said.

For this reason, there is a high concentration of melanin around the genitals of many animals, including humans. So the area is dark. The same goes for dinosaurs. Of course, it would sound odd to think of genitals while looking at a fossil that seemed to have hardened while sneaking past me.

However, the discomfort I have felt so far has been just the tip of the iceberg. Winter enthusiastically went on to describe another feature of the Psittacosaurus rump.

“Now we can reconstruct the shape of the cloaca, which is like a lip,” said Glade, making a V with his fingers. “The surface has a pigment. What’s interesting is that if it’s to prevent microbial infection, there should be a pigment around the opening, but it doesn’t. Having the pigment on the surface means it’s a pigment to highlight itself.”

If this is true, it would be surprising. Modern birds, descendants of avian dinosaurs, rarely use their buttocks to courtship like baboons do. “Algae use a lot of visual cues,” says Winter, adding that in addition to visible light, they can also see ultraviolet light. “But (algae) are covered in feathers, so it doesn’t make sense to show the cloaca.” Likewise, crocodiles are more dependent on smell.

Glade speculates that dinosaurs, like birds, must have had an excellent sense of color. “Didn’t they use the cloaca for courtship?” he asked, saying that this might be an opportunity for dinosaurs with fewer feathers.

However, it is not known whether the Psittacosaurus in question is male or female, or the shape of its penis. Therefore, it is assumed that there are two mating methods. One is the so-called “cloacal kiss,” in which two dinosaurs face a cloacal duct, as is often the case with birds, and the male releases semen directly to the female. The other is the more familiar way males use their penis (crocodiles use this way).

Of course, there is no further evidence and no other dinosaur cloacal fossils, so no conclusions have been reached.

The story of the dinosaur reproductive organs was enough. So what about the other factors involved in reproduction? Was there courtship like a fight or elaborate dance? Were males and females different in appearance? And were there any traits that could make the other person like you?

Deciphering the mating of long-extinct animals seems as impossible as finding their cloaca. But Rob Knell, an evolutionary ecologist at the University of London in Queen Mary, is convinced that the clues can be found in the fossils.

“What’s special about dinosaurs is that they have a lot of strange organs,” Knell said. “That organ is one of the elements that make up the charisma of a dinosaur. Stegosaurus bone plates, Spinosaurus big sails, Triceratops neck frills and horns, and all other Ceratopsians… the big hadrosaurs had. Nose bones… these are all candidates that could have been used to appeal to the opposite sex.”

However, scientists have debated these organs for centuries, including that hadrosaurs lived in water and that their nose bones were snorkels or air reservoirs. It was also difficult to find a plausible explanation for an institution that looked so strange. The T. Rex, for example, was first discovered in 1900, and the arm bones were too small. Since it doesn’t really appear to belong to a T. Rex, it was initially assumed that it was the bone of another animal.

Knell noted that ancient paleontologists did not interpret these organs as means of courtship. Because guessing without proof seemed unscientific.

“We don’t know what role the stegosaurus dorsal plates or the tubular bones in the hadrosaurus head played,” said Susanna Maidment, senior researcher in paleontology at the Natural History Museum in London.

Knell has been working on this topic since 2012. He paid particular attention to what he looked like as a means of courtship in living animals today. Triceratops and Psittacosaurus horns, Dilophosaurus crest, Dilophodocus long neck, and feathers of the ancestors of birds.

There is no definitive way to ascertain what these well-developed organs were used for. But Knell, along with foreign scholars, is now looking for clues in living animals.

One of them is sexual dimorphism, in which males and females have different shapes. These other parts (such as stag antlers) are used by males to directly attract females (such as the colorful feathers of male peacocks) or to compete for mating.

Unfortunately, scientists still can’t tell the difference between male and female dinosaurs. Therefore, sexual dimorphism is not useful in understanding dinosaurs. This is because there is no way to determine whether they are of the same species, but of a different sex or a completely different species, even by looking at fossils with slightly different shapes.

So you have to find something else. In animals, when a characteristic appears only in mature adults, it is often sexually related. The mane of a male lion is an example. But this too is difficult.

In 1942, a new skull was unearthed in Montana, USA. It certainly belonged to a powerful predator, but it was quite small for a T. Rex. The team assumed it was a new species, and after decades of debate, it

It was named Nautiranus. And since then, several more cases have been discovered.

In 2020, another research team entered the study. They analyzed the bones that were thought to be Nanotyranus, and concluded that it was an immature, dead T. rex. In appearance, the young animals would have been distinctly distinguished from the adults. And each would have had its own niche within the prehistoric food chain.

However, T. Rex is not the only dinosaur whose appearance changes significantly as it grows.

“Torosaurus and Triceratops were also a big topic of debate,” Maidment said. Broadly speaking, the two dinosaurs looked alike. However, Torosaurus has a huge skull and frills with huge holes around its neck. The latter, on the other hand, are much smaller and have frills without holes.

“These are dinosaurs that lived together in North America towards the end of the Cretaceous,” said Maidment. “Some think Torosaurus was a very old Triceratops, and others think they were two separate species.” “And people have argued that these are all separate species, but it may actually be the genetic (developmental) stage of Triceratops, although no one agrees.”

Considering this, the search for courtship seems to be of little use. But there are other ways. It’s to model what else the institution might have been useful (if not for courtship).

Triceratops frills are an example. For a long time, scientists have been puzzled by this gigantic organ. As a result, various explanations have emerged, such as this organ protects the neck from predators, regulates the temperature, or builds muscles to swing the horns more powerfully.

Recently, it has been explained that it may have been a means of identifying the group to which one belonged. But after investigation, Knell and his colleagues concluded that the idea was not feasible. Compared to other Triceratops species, there was little difference in the frills. As this theory potentially undermined, the frills gave strength to the speculation that Triceratops were used to court other Triceratops or fight other males.

And there is some evidence for this. A 2009 study analyzed injury patterns in the skulls of several Triceratops individuals. As a result, the injury was presumed to have been caused by fighting with another Triceratops, and the researchers left the possibility that it could be a sign of competition for reproduction.

So, what was the courtship of other dinosaurs like? Did the male T. rex wield his small arms to seduce the female? Did Pachycephalosaurs bang their heads in a battle to unleash their sexual attraction? Did male velociraptors build elaborate tree nests?

Knell is convinced that there must have been such an act on a broader scale. His rationale lies in the similarities between dinosaurs and birds, and that the ancient ancestors of birds had beaks and no teeth.

Knell said, “If you look at birds today, courtship behavior is very diverse,” and “I think it was the same with dinosaurs.” “There is no reason to suggest that only descendants of birds developed unusual mating behavior.

Surprisingly, there is also something worthy of physical evidence. In 2016, while excavating in Colorado, scientists discovered dents in an ancient puddle-like rock formation.

After investigation, the researchers concluded that these were scratches on the three toes of a predator like T. rex from the Cretaceous period. It could be a dinosaur version of today’s ostrich courtship.

Female ostriches are picky, and when males lure females, they have to do a courtship dance. Race or flap your wings and dig. Researchers hypothesized that these traces on the rocks may also have been left by dinosaurs during courtship 100 million years ago.

But Knell said the details of the dinosaur mating process would never be known. “If you try to predict it, it might not work.”

Nonetheless, in recent years, humanity has learned many things about dinosaurs that were previously unimaginable. Perhaps in a few decades we will learn more about the courtship of dinosaurs. And what kind of genitalia they had.

Zyra Govett is a senior journalist for BBC Future. Twitter account @ZariaGorvett