2020-11-06

Discovered for the first time in the world! This”shrimp” 500 million years ago is a”four-unlike” animal

By yqqlm yqqlm

The unicorn is an auspicious beast in ancient Chinese mythology. According to legend, its body combines the characteristics of a variety of animals, including lion head, antlers, tiger eyes, moose body, dragon scales, and ox tail. A few days ago,”Nature” magazine recently reported that a strange-looking fossil discovered more than 500 million years ago by scientists from the Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, is called”unicorn shrimp”, which adds another powerful hammer to the theory of biological evolution. .

So, why is it called”Kirin Shrimp”? Where did the researchers find it? What role does it play in the evolution of life? What is its scientific significance?

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Kirin shrimp fossil courtesy Zeng Han

Life has gone through a long history of about 4 billion years on earth. However, it was not until the Cambrian era more than 500 million years ago that complex and diverse life suddenly appeared on the earth. This milestone The major life evolution event of, known as”Cambrian Explosion“.

However, since Darwin, the”Cambrian Explosion” has been a major scientific mystery that plagued the scientific community. Darwin specifically mentioned in his”Origin of Species” that the sudden appearance of complex animals in the Cambrian was a huge challenge to the theory of evolution.

However, in 1984, the”Chengjiang Fauna” discovered in Yunnan by scientists from the Nanjing Institute of Geology and Palaeontology of the Chinese Academy of Sciences further highlighted the suddenness of the”Cambrian Outbreak” and brought”Darwin’s Confusion” pushed to the top. Because the discovery of fossils in the Chengjiang fauna shows that, including vertebrates, almost all modern animal phyla appeared 520 million years ago.

However, Darwin’s theory of evolution also proposed a way to solve the mystery of the”Cambrian explosion”, that is, scientists need to find the transitional ancestor fossils of the animal phylum origin.

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Kirin shrimp restoration picture courtesy Huang Diying

In Chengjiang fauna, the most diverse is Arthropods, trilobites and prawns known as”stars of the Cambrian”, are all arthropods. It is not an exaggeration to say that arthropods have been one of the most successful animals on earth since the great outbreak of the Cambrian.

Nowadays, the butterflies, crabs, centipedes and spiders that we know well are all arthropods. They have the same thing as a segmented body and appendages. It can be said that arthropods are the animals with the largest number of individuals on the earth today. They account for about 80%of the species diversity in the animal kingdom. They are found in various environments such as sea, land and air.

So, how did arthropods evolve? What did their ancestors look like? This is a major problem in biological evolution, which has plagued generations of scientists for more than 100 years. In the Chengjiang Biota, the abundant arthropod fossils have become one of the”bell-resolving stones” for”Darwin’s puzzle”.

This time, the Cambrian outbreak research team led by researcher Zhu Maoyan found the key fossil”Zhang’s unicorn shrimp” to answer the”mystery of the origin of arthropods” in the Chengjiang fauna.

The reason why it is called”Kirin Shrimp” is because it is like the”four different” auspicious beasts-Kirin” in Chinese traditional mythology, and its body is embedded with various animal morphological characteristics.

The”unicorn shrimp” is a shrimp-shaped, with five eyes, and possessed the giant predatory animal in the ocean at that time”Odd shrimp The predatory”big tongs” and the many characteristics of arthropods (such as the ubiquitous mosquitoes, insects, shrimps, and crabs) that we now know.

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p class=”pgc-img-caption”>Kirin shrimp restoration picture courtesy Huang Diying

In the Chengjiang fauna, the odd shrimp is considered to be the ancestor type of arthropods. It is the top predator with a body length of up to two meters. However, the odd shrimp There are huge differences in morphology between true arthropods and there is an evolutionary gap between the two that is difficult to bridge. This gap has become a key missing link in exploring the”mystery of the origin of arthropods.”

Kirin shrimp”, whose head is inlaid with the morphological structure of the arthropod ancestor type, including the Cambrian monster, the five unique eyes of the Opabine sea scorpion, and the predatory giant predator of the Cambrian, the strange shrimp. Feeding appendages. However, the body has obvious characteristics of true arthropods, such as hardened epidermis, healed head shell, multi-segmented torso and segmented legs.

Among the fossils of”unicorn shrimp”, the smallest is like shrimps and the largest is 7cm long.

The research team used a variety of technical methods to conduct detailed comparative anatomical studies on the fossil”unicorn shrimp”. Based on the accumulated research data of other Cambrian fossils in the world, combined with the unique chimeric morphology of the”unicorn shrimp” and the analysis of evolutionary developmental biology, the homology of the first pair of appendages between the strange shrimp and the true arthropod was demonstrated.

Researchers have reconstructed the pedigree and calculated a new model that reverses the evolutionary relationship of early arthropods and the morphological changes of appendages. The results show that the evolutionary position of the”unicorn shrimp” is between the odd shrimp and other true arthropods. It is located at the root of a true arthropod.

The”unicorn shrimp” represents an important transition fossil predicted by Darwin’s theory of evolution. It has built an intermediate bridge from the evolution of the strange shrimp to the true arthropod, filling the arthropod The key missing link in the origin process adds a powerful fossil evidence to the theory of biological evolution.

After several generations of scientists, people have gained a lot of important understanding of the mystery of the origin of animals. Far from being the end, there are still many”mysteries” waiting for us to uncover in the process of life evolution.

(The original title”A”shrimp” 500 million years ago was first discovered!”. Edit Fan Chengyou)