2020-11-06

First discovered! This”four-unlike” animal 500 million years ago will solve the mystery of the origin of arthropods

By yqqlm yqqlm

How did the arthropods evolve? What did their ancestors look like? This century-old puzzle of biological evolution may be solved by Chinese scientists.

Recently, the research team of the Nanjing Institute of Geology and Palaeontology of the Chinese Academy of Sciences discovered for the first time in the world a shrimp-shaped fossil more than 500 million years ago:it looks strange, has five eyes, and contains giant marine predators< span class=”entity-word” data-gid=”20406305″>The predatory appendages of the strange shrimp, as well as the hardened epidermis of arthropods such as mosquitoes, shrimps and crabs, healed head shells, and knotty Torso and segmented legs.

Because its body is embedded with the morphological characteristics of a variety of animals, just like the auspicious beast in Chinese traditional mythology-the unicorn, it was named”c”.

These unicorn shrimp fossils discovered by Chinese scientists in the Cambrian strata filled the process of arthropod origin The key missing link will solve the century-old mystery of the origin of arthropods, the biological evolution. On November 5,”Nature” magazine published this latest research result.

“This is another major discovery in our study of the Chengjiang fauna. The unicorn shrimp represents an important transitional species predicted by Darwin’s theory of evolution. It serves as an intermediate bridge from the evolution of the strange shrimp to the true arthropod. It adds a strong fossil evidence to the theory of biological evolution.” Researcher Zhu Maoyan, head of the research group of Cambrian Explosion, who published the paper, said .

Scientific puzzle of the Cambrian explosion

Life on Earth has gone through a long history of about 4 billion years. Why did it last more than 500 million years ago? In the Cambrian era, did complex and diverse life suddenly appear on Earth? Since Darwin, the”Cambrian Explosion”, a major life evolution event, has always 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.

“In 1984, the Chengjiang fauna discovered by our research institute scientists in Yunnan further highlighted the suddenness of the’Cambrian explosion’ and pushed the’Darwin’s confusion’ to the top.” Researcher Huang Diying, the corresponding author of the paper, explained that because fossil discoveries in the Chengjiang fauna indicate that, including vertebrates, almost all modern animal phyla appeared 520 million years ago. According to Darwin’s theory of evolution, to solve the mystery of the”Cambrian explosion”, scientists need to find transitional ancestor fossils that originated from animal species like Archaeopteryx. ”

Filling the missing link in the origin of arthropods

Among the Chengjiang fauna, arthropods are the most diverse.

“Since the’Cambrian Explosion’, arthropods have been one of the most successful animals on the planet, and they are also the most numerous animals on the planet today. According to Dr. Zeng Han, the first author of the paper, “arthropods have the characteristics of epidermal sclerosis, body segmentation, and appendage segmentation. They occupy about 80%of the species diversity in the animal kingdom and conquer the’sea, land and air’. The butterflies, crabs, centipedes and spiders we know are all arthropods.”

But the origin of arthropods has always been a mystery, and has puzzled generations of scientists.”The evolutionary relationship between arthropods in the Cambrian is still inconclusive.”Zeng Han said.

“In the Chengjiang fauna, the prawn is the top predator of the Cambrian, with a body length of up to two meters, and is considered to be the ancestor type of arthropods. However, the morphological differences between the strange shrimp and the true arthropod are huge, and there is a difficult evolutionary gap between the two. This gap has become a key missing link in exploring the mystery of the origin of arthropods.”The corresponding author of the paper and researcher Zhao Fangchen, the head of the Chengjiang Paleontological Research Station, said.

The unicorn shrimp is a”four different image” with multiple animal forms.

According to Zeng Han, the research team found 6 rare shrimp-shaped fossils in the Chengjiang fauna, the largest is 7 cm, and the smallest is only 1 cm. The researchers used a variety of technical methods to conduct detailed comparative anatomical studies on the fossils and restore them. Its shape 500 million years ago.

This animal body has obvious characteristics of true arthropods, such as hardened skin, healed head shell, multi-segmented torso, and segmented legs. However, Its head is inlaid with the morphological structure of the arthropod ancestor type, including the five eyes unique to the Cambrian monster”Opabin Sea Scorpion” and the predatory appendages of the strange shrimp. Therefore, it combines the real The physical characteristics of arthropods and arthropod ancestor types are a rare”four-unlike” chimeric animal. This is like the unicorn, hence the name.

However, it is necessary to make sure that the unicorn shrimp is in the process of evolution. Which position must go through scientific data analysis and calculation. Zeng Han introduced that based on years of accumulated research data, combined with the unique chimeric morphology and evolutionary developmental biological analysis of the unicorn shrimp, they demonstrated that the strange shrimp and the true arthropod The homology of the first pair of appendages. Through the reconstruction of the pedigree, a new model that reverses the evolution of the early arthropods and the morphological transformation of the appendages is calculated. The results show that the evolution position of the unicorn shrimp is between the strange shrimp and other true arthropod , Located at the roots of true arthropods.

The missing gaps in the evolution of arthropods have been filled. The reviewer of the research paper believes that “this perfect and unexpected transitional animal fills up arthropods. history of animal evolution of a knowledge gap”

column editor:Qin Hongwen word editor:Yang Rong thematic map source:Figure worm image editing:Su Wei

source:author:Science and Technology Daily < /p>