How to judge the gender of dinosaurs?

Almost all living vertebrates reproduce through sexual reproduction, so did dinosaurs. The sex characteristics of living animals usually have obvious external manifestations, so it is easy to distinguish males and females. For example, male peacocks have gorgeous tail feathers, male lions have long manes, and male elk have horns and are larger than females. As a Mesozoic animal, the bones of dinosaurs have been buried under the ground for tens of millions of years, and the soft tissues which can indicate gender of dinosaurs have disappeared, so it is really difficult to distinguish the gender of dinosaurs! Most of the fossils found are bones, and very few muscle tissue and skin derivatives can be preserved. So how do we judge the gender of dinosaurs from these fossils?

The first statement is based on whether there is medullary bone. When Mary Schweitzer, a paleontologist at the University of North Carolina in the United States, conducted an in-depth analysis of the “Bob” (tyrannosaur fossil), she found that there is a special bone layer in the fossil bones, which they called the bone marrow layer. The bone marrow layer appears during the reproductive and laying period of female birds, and mainly provides calcium for the eggs. A similar situation has also been seen in several dinosaurs, and researchers can make judgments about the sex of the dinosaurs. In the study, the femur of this dinosaur fossil became a key factor in identifying the sex of dinosaurs, and it is also the easiest bone to identify gender. If a layer of porous bone tissue is found around the medullary cavity of a dinosaur bone, it can be confirmed that this is a female dinosaur in the laying period. But this method is only suitable for flying dinosaurs and dinosaurs that are ready to give birth or have given birth, and cannot identify dinosaurs that are not pregnant.

The second statement is to distinguish based on the crest of dinosaurs. Archaeologists once thought that gender could be distinguished by the crests of dinosaurs, a method that was particularly suitable for Hadrosaurus. According to the extent of sparseness and position of the “crown” of the Hadrosaurus, the gender can be distinguished. But the famous paleontologist Milner disputes this, who said, “There are differences in the crowns of certain species of dinosaurs, but this can only be speculated and hypothesized.” Despite there are differences between dinosaur crests, experts have been unable to tell which crest features are male and which are female.

The third statement is to make judgments based on unique body structure. The basis is that in living mammals and reptiles, male usually use special body structures to attract females. For example, the nose of the proboscis monkey is considered to be a tool used by males to attract females. Some structures of dinosaurs are thought to be used to attract the females too. For example, the spiny nose of Tsintaosaurus spinorhinus and the crown of Guanlong wucaii may be the magic weapon used by males to attract females. However, there are not enough fossils to confirm this yet.

The fourth statement is to judge by the size of the body. The stronger adult dinosaurs of the same species may have been males. For example, the skulls of male Pachycephalosaurus seem to be heavier than those of females. But a study that challenges this statement, suggesting sex differences in some dinosaur species, especially Tyrannosaurus rex, has led to a larger cognitive bias in the public. Many years ago, a research paper claimed that female T-rex was larger than male T-rex. However, this was only based on 25 incomplete skeleton specimens. We need more bone to fully analyze the sex characteristics of dinosaurs.

It is very difficult to determine the gender of extinct animals in ancient times through fossils, but their research is more beneficial to modern scientists and has important influence on the living habits of dinosaurs. However, there are very few examples in the world that can accurately study the gender of dinosaurs, and there are very few scientific researchers in related fields.

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