How to distinguish the sex of dinosaur fossils?

  Dinosaurs were extinct hundreds of millions of years ago, leaving only a pile of fossil remains for human research and reverie. However, after studying the pile of fossils and preparing to restore it, people suddenly discovered that we hadn’t even figured out the gender of the person. Should we restore it to a beautiful “little lady” or a mighty “man”? How do paleontologists distinguish the sex of dinosaurs?
  Sexes differ
  in the existing variety of animals, including humans, we see the same kind of individual animals of different sex there is a clear difference. For example, the close relatives of dinosaurs, crocodiles and birds, male crocodiles are larger than females; male peacocks have huge and gorgeous tail feathers, and female peacocks have ordinary tail feathers; male parrots have colorful feathers, and female parrots are often gray. So, is there such a gender difference among dinosaurs?
  Some paleontologists believe that dinosaurs do have gender differences in body size. For example, some people have discovered that the skull of male Pachycephalosaurus is heavier than that of females, and some scholars have found that the skeleton of female Tyrannosaurus rex is larger than that of male Tyrannosaurus rex. They all judge the sex based on the difference in body size. However, the disadvantages of this method are obvious. The work of searching for fossils is inherently difficult. It is common for skeletons to be uneven, and it is difficult to judge the true size of the overall skeleton. In addition, the size changes of male and female in different dinosaurs are not consistent. Judging gender is obviously not very reliable.
  In addition to differences in body size, dinosaurs are also considered similar to birds. Males have some special structures designed to attract the opposite sex, such as crowns, spines, bone plates, etc., so the larger and longer parts of these parts should be male dinosaurs. Once a paleontologist used a wider head shield and a taller nose as the standard to distinguish the sex of Protoceratops. A similar situation was also found in the dinosaur’s close relative, the crocodile. A research team from Queen Mary University of the United Kingdom compared and analyzed 106 samples of Ganges crocodile and found that the nose of male crocodile has a structure called “nose fossa”, which can make the nose grow fuller and taller. No nose sockets were found on the bones. This seems to verify the feasibility of this method.
  Dinosaur mothers have characteristics
  Rather than looking for uncertain gender differences in bones, it is obviously more convincing to directly search for features that can determine the sound. For example, a dinosaur with an egg in its belly must be female. In 2009, David Unwin, a paleontologist at the University of Leicester in the United Kingdom, discovered a fossil of a Darwin pterodactyl in Liaoning Province, China, with an egg in the middle of its leg bone. The shell of this egg is wrinkled and the degree of calcification is not high, as if it was just laid. This provides a strong basis for confirming the gender of the pterosaur-researchers nicknamed it “Mrs. T”.
  Of course, there are very few cases of eggs in fossils, and other characteristics are needed to find dinosaur mothers. In mammals, in order to facilitate the production of fetuses, females have wider hip bones than males, and even female dinosaurs that lay eggs are no exception. Their hip bones are generally wider than male dinosaurs. In addition to the hip bones, dinosaur mothers also have a specialized structure for fertility, which is medullary bone.
  Medullary bone was first found in the bones of birds and refers to a calcium-rich tissue in the bone cavity of the thigh of birds. When female birds are preparing to lay eggs, under the stimulation of estrogen, calcium will fill the bone cavity to form medullary bone. Medullary bone can provide a source of calcium for the formation of eggshells. When the last egg is born, calcium will be absorbed back into the mother’s body, and medullary bone will disappear.
  Maria Schweitzer, a paleontologist at North Carolina State University in the United States, discovered a structure very similar to the medulla bone of a bird on the inside of the thigh bone cavity of a Tyrannosaurus rex fossil. Based on this, they judged that this was a young female. Dinosaur, and “she” was probably laying eggs when she died. However, although medullary bone can be used as a powerful feature of females, it only appears in female dinosaurs during the reproductive period. It lasts for a short time in the body. As a soft tissue, it is also difficult to identify in fossils. It is also very difficult to use as a basis for gender judgment.
  Obviously masculine characteristics
  most male genital placental mammal are present special kind of bone – penis bone. With this bone, males are more efficient in mating, thus ensuring that sperm can be delivered to females smoothly. And this diversified bone can help paleontologists engaged in related work to easily distinguish the sex of creatures.
  Although males in reptiles do not have penile bones, they have some bone features closely related to reproductive functions. Researchers once found a significant difference in the tail vertebrae of male and female on crocodile fossils. The first arc (the V-shaped bone under the tail vertebra) of the male crocodile’s tail bone is larger than that of the female crocodile. Some, almost 1.5 times the size of female crocodiles. This is because the male crocodile’s genitalia-the penis contractile muscle is born on this arc, while the female alligator does not have the penis contractor muscle, and the shorter pulse arc may be more conducive to the female alligator to lay eggs. The researchers used this difference to compare the skeletal fossils of Tyrannosaurus and Bald Dragons, and found that the first vein arc varies with gender.
  Dinosaurs are also likely to have an opening for excretion and mating-cloaca, like most birds and reptiles. If paleontologists find this structure in dinosaur fossils, they can also determine the sex of the dinosaur. In birds, the pubic bones in the cloaca of males are small in distance and have sharp protrusions; while in females, the pubic bones are more spaced and have no protrusions around them. The cloaca of dinosaurs must have similar characteristics. However, dinosaur fossils with cloacas are rarely found. So far, only the British paleontologist Jacob Winsell has seen this structure in a psittacine fossil.
  It seems that trying to distinguish the sex of dinosaurs from a pile of bone fossils is a very test of the luck and skills of paleontologists.

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