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Review
In the mysterious corner of the animal kingdom, there is a unique and ancient creature that carries hundreds of millions of years of evolutionary history and can be called one of the strangest animals in the world. This creature is also a common character in various myths and legends, that is, the ancient and mysterious turtle.
10,000-year-old turtle
The tortoise is an amazing creature that can both swim in the water and walk on land. The most striking feature of the tortoise is the sturdy dorsal and abdominal armor, which act like an indestructible piece of armor that protects the tortoise's soft body, allowing it to swim freely even in the water and walk flexibly when landing.
Interestingly, turtles can hide their heads, tails, and limbs in this armor, and they can use this ability to dodge enemies or cold weather.
Turtles are not ordinary birthday stars, some turtles live to be more than 100 years old, and even some legends can live to be more than 200 years old, so it can be said that they are the birthday stars of the animal world!
In Chinese culture, the turtle has a very special status. It is not only a symbol of life, but is also regarded as one of the four major gods. The ancient Chinese gave the turtle good fortune, wisdom, longevity and other beautiful symbols. Therefore, in literature, art, architecture, etc., the image and pattern of the turtle can be seen everywhere, which shows the reverence for the turtle.
The special status of the turtle derives from its natural attributes and mythological stories, in which the turtle has the image of carrying the earth, predicting the future, and having great powers. These characteristics and legends not only constitute the cultural connotation of the turtle, but also affect the way the Chinese think and behave.
Dressed in heavy armor
The skeleton structure of the turtle is unique in that it is made up of many small bones that are intricately connected to form a complex framework. This structure allows the turtle to survive in a variety of extreme environments. The skeleton structure of the turtle is mainly divided into two parts: the dorsal carapace and the ventral carapace, which is a perfect fusion of the inner and outer skeletons.
The dorsal carapace is located on the tortoise's back and is made up of the spine and ribs. The tortoise's spine is slightly rounded, which means that the tortoise is naturally a bit hunchbacked.
At the same time, the ribs continue to widen and eventually join together to form an elegant arch. On top of these bones, there are also more than a dozen scales that are formed by keratinization and ossification of the skin, which are called shields. The color and pattern of the shield can help us distinguish between different species of turtles, and it is also a beautiful decoration on their bodies.
Both the dorsal and abdominal carapaces of the turtle carry important tasks, protecting the internal organs and soft tissues of the turtle from external damage. Their shape and size also profoundly affect the turtle's lifestyle and adaptability.
In general, turtles living in water have a flatter dorsal carapace, which helps to reduce current resistance and increase swimming speed, while tortoise carapaces that live on land are relatively tall, which helps to increase volume, reduce heat loss, and better adapt to dry environments.
Some tortoises also have unique features and functions on their dorsal carapaces, such as star tortoises with star-like markings on their dorsal carapaces that can be used for camouflage and defense, while closed-shell tortoises have movable anterior and posterior bony plates that completely seal the carapace against foreign enemies.
The ventral carapace is located on the tortoise's abdomen and is the outer shell made up of the collarbone and sternopelvic bones. This part of the clavicle and sternopelvis expands outward, forming a flat plate-like shape that corresponds to the dorsal armor.
There are also scales on the ventral carapace, called the ventral plate. By the number and arrangement of the webs, we can judge the sex of the turtle. In general, the center of the abdominal carapace of a male tortoise is slightly concave inwards because the reproductive organs of a male tortoise need some space at the tail, while the ventral carapace of a female tortoise is flatter or slightly convex outwards to accommodate the needs of the abdominal reproductive organs.
One of the important functions of the abdominal carapace is to support the tortoise's body, balance its center of gravity, and aid breathing and movement. There is a gap between the ventral carapace and the dorsal carapace, called the bridge, which is the channel through which the tortoise's limbs and head retract. The length and width of the bridge have an impact on the tortoise's ability to move.
Turtles living in water usually have shorter and narrower bridges to increase the fluidity of the current, reduce friction, and improve swimming flexibility, while turtles living on land have longer and wider bridges to provide better stability, reduce inclination, and improve crawling efficiency.
Some turtles' bridges also possess unique features and functions, such as the jagged bone spurs on the snapping turtle's bridge, which can be used for defense and attack, and the mole's bridge, which has soft skin that can be used for breathing and perception.
The Mystery of Evolution
The evolution of the tortoise's dorsal and abdominal carapace has always been an important topic for scientists, and this complex and mysterious process has long puzzled researchers.
Based on the study of fossils and genes, scientists believe that the dorsal carapace was formed by the gradual widening and fusion of the ribs and vertebrae of the turtle's ancestors. The earliest evidence comes from the Triassic archaeocera, the South Turtle, whose ribs have begun to widen but are not yet fully connected.
Subsequently, the ribs and vertebrae continue to expand and connect, forming a complete dorsal armor. At the same time, the bony scales on the skin began to grow and ossify, forming shields that covered the dorsal armor, enhancing the solidity and aesthetics of the dorsal armor.
The ventral carapace is formed by the gradual expansion and fusion of the collarbone and sternum bones of the turtle's ancestors. The earliest evidence comes from the Triassic Archaeosaurus, the Semi-Carapaceed Tooth Turtle, which already had a complete ventral carapace, but no dorsal carapace.
After that, the clavicle and sternopelvic bones continue to expand and connect, forming a complete abdominal carapace. At the same time, the bony scales on the skin begin to proliferate and ossify, forming a ventral plate that covers the abdominal carapace, increasing the stability and balance of the abdominal carapace.
The dorsal and ventral carapaces are connected together by a bridge. The bridge evolved from the peripheral plates of the turtle's ancestors, which are located between the ribs and sternopelvic bones and serve as supporting the body and protecting the organs.
The earliest evidence comes from the Triassic archaeocera, the toothed turtle, which already had a complete dorsal carapace, ventral carapace, and a short bridge.
Subsequently, the perimeter plates continued to grow and deform, forming a long and wide bridge that closely connected the dorsal and ventral carapaces to form a complete carapace. At the same time, bone scales began to grow on the bridge, covering the bridge, enhancing the strength and function of the bridge.
The tortoise's bridge plays a key role in connecting the dorsal and ventral carapaces, providing the tortoise's limbs and head with access while providing space for its breathing and movement.
The combination of dorsal and ventral carapaces of turtles is a rare and unique evolutionary phenomenon that makes tortoises a unique animal. This structure gives the tortoise many advantages and challenges.
The carapace protects the tortoise's body from external damage and adapts it to different environments and lifestyles. But the carapace also limits the tortoise's size and mobility, making it slow and clumsy, making it an easy target for predators. Thus, the carapace of the tortoise is both its protector and the shackles that bind it.
epilogue
As we delve into the turtle's skeletal structure, we can't help but marvel at the strangeness of this creature. The turtle, every bone in its body contains hundreds of millions of years of evolution, making it one of the strangest animals in the world.
Beneath their hard carapace, lies the tenacity of life and the wisdom of adaptation. Perhaps, it is this unique design that makes the turtle a unique and mysterious creature on earth.
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