How did dinosaurs mate?Scientists search for answers – BBC News

Then I looked back and focused on our conversation. A particularly exciting discovery, Wensel told me, was the Yixian Formation in Liaoning, a famous fossil site in China, where two full-feathered Tyrannosaurus rex were found next to each other in what was once an ancient lake. When asked why it was special, the professor said that the pair of dinosaurs were in a strange position against each other, making them suspicious of their relationship. In fact, what he wanted to know was: Are the dinosaurs mating?

Thanks to the development of modern science and technology, scientists are now making amazing discoveries at a record rate, many of which were unimaginable just a few decades ago.

Research in molecular biology has determined that 76 million years ago theropod dinosaurs had red blood cells and collagen. Among this group of dinosaurs was the Tyrannosaurus rex, which was once the largest carnivore on earth. Indicative chemical signatures found in the study suggest that Triceratops and Stegosaurus were rare cold-blooded dinosaurs, and another spiky, heavily armored, herbivorous jellyfish had a reddish-orange appearance. Scientists also found that Spinosaurus, known for its “giant sails” on its back, likely used its 15cm teeth and crocodile-like jaws to hunt in deep water, and evidence that Iguanodon may have been surprisingly smart and could fly. The pterosaurs (certainly not strictly dinosaurs, actually classified as winged reptiles) often walked in search of prey.

However, exactly how dinosaurs mate, or any research on dinosaur mating and reproduction, has so far been completely blank. To this day, scientists can’t even tell for sure whether dinosaur fossils are male or female, let alone how dinosaurs courted and mate, or what kind of reproductive organs they had. Without these basic knowledge, most of the physiological phenomena and behavior of dinosaurs will remain a fog. One thing’s for sure, though: Dinosaurs definitely mate.

Returning to the topic of T. rex fossils just now, Wensel explained that to solve the mystery of the strange posture of the T. rex, another ancient lake site in Germany, the Messel Pit (Messel Pit) (Messel Pit) can provide a clue. The Messer Stone Pit was originally a quarry, and later became famous for the discovery of a large number of well-preserved animal and plant fossils, which is now listed as a World Natural Heritage. The animal and plant remains preserved in this fossil paradise look like they were squeezed into a book. The fossils researchers have found so far include fox-sized horses, giant ants, early primates, and several animals with a full stomach. beetle. A large number of freshwater turtles were also found, of which at least nine pairs died suddenly during mating. Several pairs of tails are still touching when mating. The mating pattern of freshwater turtles in the Messer Fossil Pit has significant implications for Wensel’s theory of dinosaur mating.

The reason why Messer Pit is a prehistoric burial ground for an enormous number of ancient animals comes from a poisonous secret. In the geological age of the Eocene, 57 million to 36 million years ago, the Messer Crater should have been a steep, water-filled crater surrounded by dense subtropical forest. There is no scientific conclusion as to how this volcanic lake caused such a sudden death of flora and fauna. One hypothesis is that there was still active geological activity after the lake formed, periodically releasing life-suffocating carbon dioxide mist around it. These unfortunate sea turtles may have been trapped and killed in a carbon dioxide fumes release event and then sank to the bottom of the lake, where their mating posture was preserved for tens of millions of years in an oxygen-deprived layer of silt.

However, these freshwater turtles, who were “lusting up” at the time of their death, were not exactly the same as they usually do when they were riding on one back to mate, but turned their backs to their backs, as if the two turtles had suddenly changed their minds and wanted to away from each other.

Professor Wenther sensed my confusion and leaned back in his chair to explain that the mating freshwater turtles should have gradually separated their bodies after they died, but remained connected because the genitals were still connected. Winther’s expression suggests that he thinks discussing prehistoric animal sexuality is simply a normal subject.

Freshwater turtles mating from Messer Pit are back on this oddly-posed T. rex fossil for some uncanny resemblance between the two lovers. The T. rex “was separated from each other, but the tails were overlapping each other,” Winsel said. “I think the T. rex pair had a sudden mishap during mating.”

Apart from this, there is no other case evidence, and Winther admits that his theory is based on a highly hypothetical, so far unpublished idea. There are still many fossils of soft organs in dinosaurs that have not yet been discovered. If this pair of Tyrannosaurus Rex is really trapped and locked in an ancient copulation, this phenomenon will reveal some information about some kind of dinosaur soft organs. That’s right, that means Tyrannosaurus, and possibly Tyrannosaurus rex, probably had a penis.

However, there is another clear source of information about the truth about dinosaur sex, a fossil that has captured the world‘s attention with its lower body. This is the aforementioned Parrotosaurus.

Winther showed me this treasure in his collection and explained to me the ins and outs behind it.

This is an ancient ecosystem in Northeast China, the Early Cretaceous Jehol Biota. Let’s assume it’s a sunny day, and in this temperate land, Parrotosaurus decided to leave its wooded home and head to one of the many lakes in the area to drink to quench its thirst. About 91 centimeters long from head to tail, Psittacosaurus is reminiscent of an unusually stocky Labrador retriever, almost an adult but not yet sexually experienced.

Tragedy ensues when this psittacosaur walked to the lake on two feet, as it stopped walking on four as an adult. Just as it was bending over to take a sip of water with its parrot beak, it slipped and fell into the lake and drowned. When it fell to the bottom of the lake and lay down indecently on its back, it accidentally preserved its genitals so that it could be pondered by future humans.

Of course, Wensel especially wanted me to see this famous lower body. He pointed to a black, circular piece of skin under the Psittacosaurus tail, the dinosaur’s private parts, which have been preserved through the ages since the early Cretaceous. That era was so far away, a time span equivalent to 1.6 million times the average human lifespan today.

Alas, the Parrotosaurus in Wensel’s office isn’t an actual fossil, what I’m seeing now is a full-scale model commissioned by him himself. But the model is perfect, meticulously crafted, and the precise stripes found on the original fossil skin are reproduced as closely as possible, even the markings.

So, what information can this little dinosaur’s private parts give us?

First, like its close relatives such as birds and crocodiles, this dinosaur also had a cloaca. The cloaca, a versatile excretory opening, is common in all terrestrial vertebrates except mammals. This is a single orifice for defecation, urination, intercourse, and production. It’s not unexpected, but it’s a new finding, as no one has previously confirmed that dinosaurs shared the same reproductive structure with their evolutionary cousins.

“So you can look and see that there’s a lot of pigment underneath (he pointed to the cloaca under the tail of Psittacosaurus),” Professor Winsel said. He explained that it’s melanin, and it’s possible melanin was so important to the preservation of this fossil, he explained. Goodness worked.

While we generally only know melanin as the dark compound that gives our skin its color, melanin has countless uses in the natural world, from squid ink to the protective layer behind our human eyes. Melanin is also a potent antibacterial agent, usually found in high concentrations in the livers of amphibians and reptiles, and its function is to prevent the growth of potentially harmful microorganisms. But crucially, melanin has also been found to play a protective role in many other living environments.

“Insects, for example…use melanin as an immune system to protect themselves from infection. So if you poke a hole in a moth with a needle (which I don’t recommend), you poke around the hole It secretes melanin,” Professor Winsel said.

Because of the immune function of melanin, in many animals, including humans, the concentration of melanin around the genitals will be higher, so the skin color in this area will also be darker. Dinosaurs do, and so do humans. Looking at this distant human relative in front of me, as a colleague of mine pointed out, I felt as if it was frozen forever in this pose as it passed me, finding dinosaurs so close to us, It feels weird.

But there are more interesting discoveries, obviously, all my weirdness so far is just a warm-up, and there’s a lot more to come. Before I knew it, Wenther began to enthusiastically explain to me many other features of the lower body of Psittacosaurus.

“Now that we can reconstruct what the cloaca of Psittacosaurus looked like, we can show that it had two lips that were open like this,” says Professor Wensel, who spread his fingers in a V-shape. “There is melanin outside the opening. But the interesting thing here is that the melanin is not at the opening (if it is to prevent microbial infection, the melanin should be at the opening), so the melanin is placed outside for publicity and show.”

If this were true, it would be unheard of like baboons showing off their hips to the opposite sex, since such courtship is extremely rare even among the descendants of avian dinosaurs, modern birds. Dinosaurs “use a lot of visual cues,” Winsel said, explaining that dinosaurs had excellent color perception, unlike most mammals who can only see two colors, while birds can see three colors that humans can recognize in addition to In addition to the color, ultraviolet rays can still be seen. “But it doesn’t make sense for birds to show their cloacas because they’re covered with feathers.” Likewise, crocodiles rely more on scent to attract mates.

Winther speculates that, like birds, dinosaurs may have had excellent color vision, in which case those dinosaurs without feathers might have taken the opportunity and said, “Why not show your cloaca?”

Unfortunately, we can’t tell if this Psittacosaurus was male or female, or what kind of sex organs it had, since each of its sex organs are hidden in the cloaca. This leaves two possible mating strategies. Or the so-called “cloacous kiss,” in which two dinosaurs are stacked on top of each other, and the males inject semen directly into the females’ cloacas through the cloaca, a common mating strategy among birds. Or the more familiar version, which uses penis mating, which is the case with crocodiles.

Since there is no further evidence, and no other dinosaur cloaca fossils to study, the above opinion is inconclusive.

Probably enough has been said about dinosaur genitals. So what about other aspects of dinosaur mating and reproduction? Will there be a courtship ceremony? Such as same-sex fights for the opposite sex, or even elaborate dances? Do males and females look different? How can we tell which characteristics of dinosaurs are to attract the opposite sex?

At first glance, deciphering the mating behavior of long-extinct animals may seem like an impossible task to find fossilized lower bodies. But Rob Knell, an evolutionary ecologist at Queen Mary, University of London, assures me that there are clues hidden in the collected fossil record.

Nair told me, “One of the things that’s been done about dinosaurs is that there’s a lot of weird stuff in them, some people call them ‘weird structures.’ And that’s one of the charms of dinosaurs. So the roulette wheel on Stegosaurus, The large sails on the spines of Spinosaurus, the frills and head horns on Triceratops and other ceratopsians, and the large crowns on hadrosaurs are all good traits for sexual selection.”

For 200 years, scientists have debated the function of these bizarre structures in dinosaurs, often with outlandish theories such as hadrosaurs being aquatic animals whose crowns served as snorkels or air chambers. Sometimes it is difficult to believe because the shape of dinosaurs is too strange. For example, when the Tyrannosaurus Rex fossil was first discovered in 1900, it was found that its forelimbs were too small compared to its huge body, so it was not believed that it belonged to Tyrannosaurus Rex itself. The skeleton was originally thought to belong to another dinosaur.

But Nair explained that in the past, paleontologists were reluctant to interpret these bizarre shapes as a tool for attracting opposite sex or same-sex rivalry. They could speculate that this might be the ultimate purpose of the dinosaurs, but it seems unlikely that the hypothesis will be proven. Not a scientific attitude.

Susannah Maidment, senior researcher in paleontology at the Natural History Museum in London, said: “The disc-like thing on the back of Stegosaurus is an example. Or the tubular crown on the head of the hadrosaurus. … we don’t know what they’re used for.”

Then entered the era of contemporary scientific research. Back in 2012, Nair had decided to take the issue further seriously. He is particularly interested in studying eccentric traits that closely resemble the mating behavior of animals in the present-day world, or traits that cannot be explained by other theories. Examples include the head horns and frills of Triceratops and its relative Psittacosaurus (with unusual side spikes on its cheeks), such as the crest of the predatory dinosaur Dicryosaurus, which had a prominent protruding above each eye. Ridgelines, in addition to the long necks of giants like Diplodocus, and the feathers of the dinosaur ancestors of birds.

While there was no definitive way to determine what these strange body structures were used for, Nair and an international team of scientists soon realized that convincing intelligence clues could be found in the animals that live in the world today, of course you Must know where to look.

One way to look is sexual dimorphism, which is when males and females of a species look very different. The two sexes are rarely radically different in terms of lifestyle and survival strategies, so differences in appearance are usually done so that males can directly attract females (such as the male peacock’s colorful feathered cloak) or compete with the same sex for mating rights (such as antlers of a stag).

Unfortunately, this particular tip does little for understanding dinosaur sex, because scientists can’t yet tell the difference between males and females, and even if they find differences between individual fossils, they can’t be sure if they’re seeing a dinosaur of a different sex, or whether they’re looking at it. Different dinosaur branches.

This leads to the next tip. If a feature is only found in adult dinosaurs and not in infants or juveniles, the feature is usually for sexual reproductive function, just as a male lion’s mane is considered a sign that a male lion is eligible for sexual mating . However, getting started on this is also tricky.

Back in 1942, scientists unearthed an astonishing new skull dinosaur fossil in Montana, USA, apparently belonging to a terrifying predatory dinosaur, but nothing compared to the ultimate predator king, Tyrannosaurus Rex. Small and slender. The team thus concluded that this was a new species of adult dinosaur, and after decades of debate, the discovery was finally named Dwarf Tyrannosaurus. Over the next few years, several more skeletons were discovered that may have been this so-called dwarf tyrannosaurus.

Then in 2020, a scientific team took a closer look. They analyzed the skeletons of two probable dwarf tyrannosaurs, and realized that this might not be another species at all from T. rex, which was T. rex, but died in adolescence before it was fully developed. Tyrannosaurus rex. In fact, there is a misunderstanding because these smaller, juvenile tyrannosaurs looked so different from adult tyrannosaurs that it almost looked like they were really two unrelated species, each occupying a separate place in the prehistoric food chain. in a unique location.

Tyrannosaurus rex isn’t the only dinosaur that has evolved to undergo dramatic developmental changes.

“There’s a lot of debate about Booceratops and Triceratops,” Medment said. Although the two dinosaurs look very similar, the former had a very large skull, one of the largest of any land animal, and a neck. It has a huge ring-shaped ruffle with a huge hole in it. The latter is much smaller in stature, and has no holes in the smaller neck ruffles.

“These are two dinosaurs that lived in the same area at the same time,” Medment said. “Both lived in North America at the end of the Cretaceous period. Some people think that the bovine horned dragon was a later triceratops, and some people think they were Two different species.” She also cited other variants of what some people think are just different life stages of Triceratops. “It’s been argued that these are different species, but in reality, it’s possible that it’s just Triceratops at different stages of ontogeny. Dragon. But no one really agrees.”

Therefore, this strategy of identifying features is not necessarily effective. But luckily, there is another way, and that is to model other aspects of this body structure that might be useful.

“All we can do is, well,[the modeling results suggest]this is consistent with structures that have evolved for this purpose (mating), and not with structures that have evolved for any other purpose,” Nair said.

The giant frill of Triceratops is an example. For years, successive generations of scientists have puzzled over the gigantic physical features of Triceratops, with various speculations, such as protecting its neck from predators, or regulating body temperature, or even saying it was just for the triceratops The dragon provided a place for the muscles to attach so that the Triceratops could swing its head horn more powerfully.

More recently, it has been suggested that neck frills may have been used to help Triceratops identify members of their own group. So, Nair and his colleagues did further research and found that this idea didn’t work, because frills varied little across species of Triceratops, so it’s unlikely that frills evolved for the purpose. Since this theory may not hold, we can reasonably speculate that its real purpose was to impress other Triceratops or to repel other males to get a chance to mate.

Here comes the evidence. In a 2009 study, researchers analyzed injury patterns on the skulls of several Triceratops and found that they were consistent with other Triceratops fighting trauma. Researchers may have uncovered the lingering ghost of ancient animal mating competition.

Are there other courtship mating rituals? Could male Tyrannosaurs really wiggle their tiny forelimbs to attract females to mate, as the producers of the TV show “Prehistoric Planet” recently said? Could Pachycephalosaurus be headbutted to win in the battle for sexual mating? Do male raptors build elaborate pergolas to please the opposite sex, perhaps choosing only the bluest berries to adorn their masterpieces?

Nair believes that, broadly speaking, there should be other mating rituals. He points out that there are many similarities between dinosaurs and birds, and that in fact, today’s birds are blood descendants of their ancient feathered dinosaur cousins, with beaks and missing teeth. So bird dinosaurs are more similar to today’s birds, such as velociraptors, more like murderous turkeys than the slick-skinned carnivores of the Jurassic Park movies.

“If you look at today’s birds, you’ll see a wide range of courtship styles displayed by birds,” Nair said. “Why couldn’t dinosaurs? There’s no reason to think that dinosaurs didn’t have some strange mating traits that birds didn’t inherit… So, I think dinosaurs had weird mating styles.”

Surprisingly, it might even be possible to find physical evidence of dinosaurs’ bizarre courtship behavior. In 2016, when scientists dug in Colorado, they discovered some peculiar rock beds that almost resembled ancient puddles.

However, a closer look revealed clear scratches and three-toed footprints on the rock bed, which were left by predators such as Tyrannosaurus rex during the Cretaceous period. Rather than accidental undulations on the land surface, these imprints were created by dinosaurs and look like enlarged versions of imprints left by ostriches today.

Female ostriches are difficult to please very fastidious lovers, so male ostriches must perform complex courtship dances to get the female to fall in love. The complex courtship ritual also includes a sprint with vigorous wing flapping and a “ground scraping ritual” to demonstrate its digging skills, as it is a skill required to build a nest on the ground. The researchers believe that the scratches left on the rock bed of Colorado, T. rex may have done the same courtship behavior 100 million years ago.

However, Nair argues, we may never know the odd details of most dinosaur mating rituals. Even extant dinosaur relatives, such as the various birds of paradise, have a variety of mating rituals. “Even if you want to predict, you’re not going to get very far,” he said.

But in recent years, humans have learned a lot about the life of dinosaurs that was previously unimaginable. Who knows, maybe in a few decades, with the advancement of technology and the growth of knowledge, the strange courtship methods of dinosaurs will be deciphered by humans one by one, and the amount of information in this area will be disturbing. Yes, then we’ll know exactly what dinosaur genitalia looked like.