Why does a turtle retract its hands and feet into its shell when it is in danger, instead of "escape"? They say that a tortoise’s shell is its shell, why can’t it be taken off?

This is actually related to its unique body structure. According to scientists, this set of tortoise shells is not just a shell. Not only that, the tortoise is also one of the animals with the strangest body structure in the world.

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History of turtle shell evolution

Before answering this question, let’s first talk about how turtle shells evolved.

The Siberian Cuposaurus lived during this period. Compared with other animals, it had thick armor on its back, which could resist the bites of the ancient mammal Orgydon.

In this case, the Siberian Cuposaurus can go out to look for food without any distractions. Because its body structure has many similarities with turtles, many scientists regard it as the ancestor of turtles.

Compared with other animals, the Siberian Cuposaurus has thick armor on its back, which can resist the bite of Orgydon. In this case, the Siberian Cup Dragon can go out to look for food without any distractions. Because its body structure is very similar to that of a turtle, many scientists regard it as the ancestor of the turtle.

By the Triassic, the era of Siberian Cuposaurus gradually declined. Instead, there is a creature called a half-armored turtle. The reason why it is called a half-shelled turtle is mainly because the carapace of this turtle is not fully developed.

According to the existing fossils, the ribs of the turtle have become wider and connected to form a complete plastron, but there are only a few ossified turtle plates on the back spine, and the entire turtle shell Not complete.

Scientists analyzed that this is because the belly is most vulnerable to attack when it lives in water, so it gives priority to protecting the belly.

Compared to tortoises, the Tortoise is a semi-finished product. If we go back to the Triassic era, the Tortoise would definitely be a living target for predators, and they would not be able to resist even if they wanted to.

Of course, as time goes by, the turtle shell gradually becomes complete, such as the Zhengnan turtle at the back, and its carapace slowly begins to develop. At this time, the turtle clan can face the enemy head-on.

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By the time of the ancestral tortoise, its ribs were not much different from the plastron of today’s tortoises. However, it has not yet been proven that there is a genetic relationship between the ancestral tortoise and the ancestral tortoise. Therefore, the evolution of the tortoise The process is not yet completely clear.

Later came the age of the turtle. As the ribs of the turtle became denser and denser, the turtle plate formed from the vertebrae became more and more complete, and the clavicle of the chest also began to close. At this time, its tortoise shell is already impregnable. As long as its limbs, head and tail are retracted, even if it is hit with a stone, it will be difficult to break open the tortoise shell.

In other words, the turtle shell is actually its spine and ribs. It is a gradually evolved composite structure. It is neither a shell like a hermit crab nor an exoskeleton like a shrimp and crab. Therefore, it is The unique turtle is also jokingly called an "extraterrestrial creature" by scientists.