65 million years ago, dinosaurs were the overlords of the earth, and their reign spanned the entire Mesozoic (Triassic, Jurassic and Cretaceous) for 161 million years, although dinosaur fossils have existed on the earth for tens of millions of years, but it was not until the 19th century that people knew that there were such strange animals on the earth. Dinosaurs at the time were known as terrifying lizards.
After 200 years, humans have a general understanding of dinosaur species, living habits, etc., and at present, one of the biggest unknown problems for dinosaurs for scientists is how dinosaurs mated.
Because through the habits of dinosaurs: breathing with lungs, egg-born, not breastfeeding, scientists have found that dinosaurs must mate to reproduce, but biological mating is difficult to preserve through the form of fossils.
The currently known fossil record includes a pair of 47 million-year-old turtles and a pair of 320 million-year-old sharks, both of which were quickly buried and fossilized during mating. Unfortunately, we haven't found any dinosaur fossils that died in romantic embraces. Even though some dinosaur fossils are extremely well preserved, the reproductive organs are still unrecognizable.
Now that dinosaurs are only fossils, how do scientists distinguish between males and females of dinosaurs that have become fossils? Scientists have found that there is a layer of tissue called "medulla bone" in the femur of the fossil leg of the dinosaur, that is, the female. This layer of tissue stores calcium in preparation for egg laying, which means that female dinosaurs also produced a calcium layer in the femur, at least when pregnant.
But what kind of reproductive system dinosaurs existed, and in what way they mated, is far beyond the current level of research, which makes the academic community put forward many hypotheses.
The reason for this situation is that there are many types of dinosaurs, physical characteristics are really complex, and the size differences are very large, some time ago, scientists found the skull of the smallest known dinosaur ever known in the Cretaceous amber of Myanmar, weighing less than 2 grams and growing between 6-12 centimeters. The largest brachiosaurus was 25 meters long and 15 meters high, and the brachiosaurus had longer forelimbs and a shorter tail, so brachiosaurus could not stand on its hind limbs like a diplodocus.
In addition to this, like spinosaurs, saber-toothed dragons, stegosaurs. And so dinosaurs have defensive spikes on their backs. Another example is a dinosaur like Tyrannosaurus rex, with a tail length of 4 to 6 meters.
At present, scientists have found by reconstructing the growth curve of dinosaurs that many female dinosaurs already have medullary bones at the age of eight or nine, which indicates that they have been pregnant, rapid growth rate and early sexual maturity, which may indicate that dinosaurs are struggling to survive in a dangerous environment, and they have to reproduce the next generation as soon as possible through early breeding to maintain the continuation of the population.
Hypothetical growth curves of four Tyrannosaurus dinosaurs
Juvenile feeding is especially important for the largest dinosaurs. If a 24-meter-long dinosaur, such as Apatosaurus, took decades to reach sexual maturity, only a tiny number of individuals would survive and give birth.
As for how they mate and reproduce, Rogers, an assistant professor of biology and geology in the United States, said in an interview with the Discovery Channel:
Dinosaurs were most likely to mate in the same way as mammals today, that is, crawling and straddling, and other than that, they were not operable.
Many scientists agree with this explanation, they believe that the leg bones of dinosaurs can withstand four to five times the weight, those bone plates are not motionless attached to the spine, but are connected to the skin and muscles, can be shaken left and right, like porcupines or hedgehogs, although there are a lot of lethal weapons on the back, but in fact, those thorns are not erect when the muscles are relaxed, but close to the skin, and elastic.
Like a porcupine or a hedgehog, although there are a lot of lethal weapons on their backs, in fact, those thorns are not upright when the muscles are relaxed, but close to the skin, and they are elastic.
However, some scientists believe that some female dinosaurs with spines on their backs or large bodies are lying on their sides to avoid stabbing and bearing the male's large weight, and biologist Stuart Landry said that large dinosaurs can easily fall down when mating on land, and they need water to provide support.
On the question of whether dinosaurs had the same reproductive structure as mammals, the famous biologist Xing Lida believes that dinosaurs have the structure of the cloaca:
We speculate that dinosaur reproduction should have been similar to today's reptiles. Males have a pair of reproductive interfaces, called hemipenis, which are usually hidden at the base of the tail, that is, in the cavity behind the cloaca. Now can you imagine two 80-ton brachiosaurs mating, that would be so shocking? The concept of 80 tons vs 80 tons is equivalent to two groups of 16 African elephants weighing 5 tons each at high speed, which is a really aphasia. Most likely, the male carp used its tail as the third support point when the front legs were vacated, and combined with the legs to form a "tripod". Because only by allowing the tail to bear a share of the weight, the mating behavior of brachiosaurus can be established.
Xing Lida has this speculation because snakes, lizards and some marsupials have the structure of the cloaca. They all have a cloaca, a cavity at the very end of the body that combines reproductive, urinating, and defecation functions. Therefore, Xing Lida speculated that dinosaurs probably had similar organs. As a result, the reproductive system of a confused dragon may normally be invisible, and the appearance is only a slit under the tail.
This allows you to hide inside your body to prevent being attacked by the enemy. Especially for powerful carnivores such as tyrannosaurs, if exposed, it is easy to be attacked by smaller social carnivorous dinosaurs.
But some scientists believe that dinosaurs did not have such a structure as hemipenis in their reproductive cavities, but instead squeezed jz into the female cloaca by means of "cloaca kisses" like birds.
However, many scientists also believe that humans have found more than 1850 genera of dinosaurs, they lived between 245 million years ago and 66 million years ago, in the long evolution, their external genitalia are likely to have a lot of changes, different species of dinosaurs may have different mating methods, although we humans divide them into dinosaurs, but in fact their structure is very different.
For example, about 22 meters long Mamenxi dragon does not have a closed vas deferens, dd may be up to three or four meters long, and the flying dinosaurs of pterosaurs rely on the structure of the cloaca, whether there is hemipenis, it remains to be examined, those in the water, etc., there may be two like some snakes, which side is convenient to come to which one!
Mammon Creek Dragon
But in any case, if humans can understand how dinosaurs mate, then humans will have a better understanding of the development, evolution and reproduction of dinosaurs, which is of great significance for studying the evolution and reproduction of species.